The Messenger
No. 124 – June 2006 Telescopes and Instrumentation
CRIRES: Commissioning of the MACAO Adaptive Optics Module and General Status Report
Hans Ulrich Käufl, Raul Esteves, veloped for the interferometry feed of the ment. This approach is also very much in Enrico Fedrigo, Domingo Gojak, VLT UTs, but were later also used for the line with the reintegration process at Jean-Louis Lizon, Enrico Marchetti, VLT instruments SINFONI and CRIRES the VLT. The integration, alignment and Sylvain Oberti, Jerome Paufique, (see Arsenault et al. 2004, Bonnet et al. testing of the AO part require special Eszter Pozna, Sebastien Tordo (ESO) 2004 or Paufique et al. 2004; alternatively tools and a special test camera which in one can consult the ESO AO webpage turn require a sequential integration at the http://www.eso.org/projects/aot/ which telescope. The CRIRES warm-optics The installation and commissioning of contains detailed information). acceptance review took place at ESO on CRIRES, the Cryogenic Infrared Echelle 24 February 2006, and thereafter packing Spectrograph, marks the completion In mid-2005 the assembly and integration and shipment of the units could start, of the original plan for the first genera- activities of CRIRES had progressed such subject to few additional checks. Packing tion of VLT instrumentation. Here we that the in-depth verification of the per- of the ‘warm optics’ finally started on report on the commissioning of the cur- formance could be started. As the re- 28 February 2006 and the crates left ESO vature sensing adaptive optics part quirements on stability and reproducibility Headquarters on 8 March 2006. All (MACAO) of CRIRES in April 2006. This are relatively demanding this test phase boxes of this first batch arrived in good activity also brings the quasi-series pro- resulted in requests for a variety of modi- order on Paranal on 17 March and duction of the MACAO systems to an fications which did not allow keeping the were met by a joint team of the ESO In- end. All four UTs are now equipped with original schedule. strumentation and Telescope Systems one MACAO system each to feed inter- Divisions. Reintegration and installation of ferometry while UT1 and UT4 have one However, in February 2006 CRIRES ulti- the components progressed rapidly with additional dedicated system each inte- mately passed the last fundamental mile- hardly any problem. grated into instruments. A summary of stone on its way to the VLT: the success- the overall status of CRIRES is given as ful completion of an ‘end-to-end’ test In the meantime, the CRIRES cold part well. of the system. Using a simulated cool star underwent further improvements and (black-body source and a gas cell with testing in Garching. By the time of writing CO mimicking a COmosphere1) and a tur- of this article the PAE for the complete CRIRES is a cryogenic, pre-dispersed, bulence generator to generate ‘seeing’, instrument had been granted and the infrared echelle spectrograph designed the overall stability of the system, that is spectrograph arrived in good order on to provide a resolving power l/Δl of the Adaptive Optics System and the Paranal on 5 May. The commissioning of 105 between 1 and 5 μm at the Nasmyth cryogenic spectrograph, was checked by the complete instrument will be reported focus A of the 8-m VLT Unit Telescope 1 recording spectra over many hours. in the next issue of The Messenger. (Antu). A curvature sensing adaptive op- The result of this test was that vibrations tics system feed is used to minimise slit and other instabilities are generally at losses and to provide diffraction-limited a level of the equivalent of 1/20th of a Testing the adaptive optics at the spatial resolution along the slit. The nomi- pixel (75 m/s Doppler shift equivalent) or telescope nal slit width of CRIRES is 0.2 arcsec. less and thus in line with the specifica- tions reflecting the astrophysical require- The commissioning of the warm-optics A mosaic of four Aladdin III InSb-arrays ments. part ran in parallel with the final pre- packaged on custom-fabricated ceramics paration for the second part of the PAE. boards has been developed. This pro- Thanks to the joint efforts of the team vides for an effective 4096 × 512 pixel How to move CRIRES from Garching and of Paranal staff, the integration and focal plane array, to maximise the free to the VLT realignment of the warm part in Paranal spectral range covered in each exposure. were successful: the MACAO system is Insertion of gas cells to measure high- Like any other VLT instrument, CRIRES now functional at full performance level. precision radial velocities is foreseen. had to pass the scrutiny of a review Spectro-polarimetry (circular and linear before shipment, termed PAE (Preliminary Figure 1a shows the adaptive-optics part polarisation) will be added in the course Acceptance Europe) in ‘ESO-speak’. of CRIRES after reintegration. For test of the project. To that end a cryogenic CRIRES consists of two relatively inde- purposes an infrared test camera with Wollaston prism in combination with re- pendent subunits: the adaptive optics a spatial sampling of 17 mas/pix (milli-arc- tarders for magnetic Doppler imaging part with the derotator, also carrying the seconds per pixel) was additionally in- is foreseen. CRIRES is part of the initial calibration facilities and the cryostat stalled to characterise the AO perform- first-generation instrumentation com- with the cryogenic optical bench. Hence ance (to be compared with the diffraction plement and is an in-house project done it was decided to split the PAE process limit: e.g. 1.2 l/D = 45 mas at 1.45 μm). by ESO (for an in-depth description of in two, and to have the ‘warm optics’ part In fact, once CRIRES is installed with its CRIRES see e.g. Moorwood 2003 or reviewed ahead of the rest of the instru- infrared slit viewer, the sampling – Käufl et al. 2004). The CRIRES MACAO system carries series number 6 of the 1 COmosphere is a term coined by Tom Ayres to highly successful ESO curvature sensor account for the very special chromospheres of cool AO systems which were originally de- stars dominated by the CO-molecule.
The Messenger 124 – June 2006 Figure 1a: A view of the CRIRES ‘warm optics’ near- Figure 1b: A team member, trying to sort out and re- ly completely installed on the Nasmyth A platform of connect the fibre bundle connecting the wave-front Antu (aka VLT UT1). The left electronics rack houses sensor lenslet array with the 60 avalanche photo di- most of the entire AO related electronics, that is the odes (APDs) contained in a special cabinet. The real-time computer, the local control unit (LCU), the APDs are solid-state photon-counting detectors. As adaptive mirror control and the power supplies for all curvature wavefront sensing systems basically need motors. Moreover the warm optics part comprises only one fast photometric channel per sub-pupil, the calibration unit with continuum sources, spectral APDs were given preference over CCD-detectors, lamps and the gas-cell slide, which allows to port due to their extremely low noise level (typically the ‘Iodine-cell-method’ for high-precision radial-ve- 0.4 counts per loop cycle). APDs, however, are very locity measurements into the infrared. The electron- sensitive and fragile devices, and the prevention of ics rack in the centre is an auxiliary rack for the in- accidental (and catastrophic) overexposures is a key frared test camera (which can be seen on the right issue. side in preparation: the shiny cryostat cylinder on a blue table). At this point a normal CCD camera is still used for alignment. For the reflection in the centre, see Figure 1b.
45 mas/pix – is no longer well suited to showing up as a ‘hot spot’2. The system 4–13 August 2006. In mid-June there will explore the AO-image quality (this cam- has proven its stability by observing in all be a first call for proposals for science era scale was chosen to be able to ex- typical seeing conditions from 0.5 up to verification programmes and at this point plore a larger field for offset-guiding). 1.5 arcsec. For bright stars with mR < 11, CRIRES will most likely be included in Figure 1b shows part of the integration. Strehl ratios in K-band above 55 % are the next call for proposals (P79). More obtained for median seeing conditions science verification is planned for P78
Figure 2 (next page) shows details inside (0.8?, t0 between 3 and 4 ms at 0.5 µm), (1 October 2006 to 31 March 2007) and the MACAO box. The commissioning at the level of performance of the other potentially also an early start of opera- culminated within a few minutes of twi- MACAO units. tions of CRIRES for normal programmes light on 3 April to check the derotator selected by ESO’s OPC through the nor- algorithm. Official first light for the adap- mal selection process. tive optics part with the infrared test Outlook camera was on 6 April when the AO con- trol loop was closed at 23h24 UT on the The commissioning of the complete sys- References 5th-magnitude B-star Muscae. The tem is ongoing and everything is pre- h Arsenault R. et al. 2004, The Messenger 117, 25 following commissioning tasks could be pared for first light on 4 June. A second Bonnet H. et al. 2004, SPIE proc. 5490, 130 finished so smoothly that the team gave commissioning run and potentially some Käufl H. U. et al. 2004, SPIE proc. 5492, 1218 back one night of commissioning time. science verification are planned for Moorwood A. F. M. 2003, The Messenger 114, 5 The AO system characteristics are sum- Paufique J. et al. 2004, SPIE proc. 5490, 216 marised in Table 1 and Figure 3 (next 2 The first author remembers that during the time page) shows – as an example – an image of his thesis project 20 years ago, 1 arcsec im- of Io, the innermost Galilean moon of age quality on a 2–4-m-class telescope was con- Jupiter with one of its active volcanoes sidered ‘excellent’ and 2 arcsec was certainly average quality. Against this background, the im- ages shown here constitute an amazing achieve- ment of technology.
The Messenger 124 – June 2006 Telescopes and Instrumentation Käufl H. U. et al., CRIRES: Commissioning of the MACAO Adaptive Optics Module
F/15 Nasmyth focus
Optical derotator
DM + TTM
Wavefront sensor
Dichroic
Figure 2: A close view of the optical path with the the corresponding optical spectrograph (UVES). protective cover removed. The mirror labelled ‘DM + TTM’ stands for deformable mirror in fast tip- ‘Dichroic’ will be replaced at some point in late June tilt mount. It should be noted that the complete by the CRIRES Cryostat Entrance Window. The AO wavefront correction comes at the expense of dichroic shown here on a provisional mount will then only four extra reflections. The optical derotator become part of the CRIRES vacuum vessel. This is based on the one used in the VLT UV and Visible mirror separates the light path at a transition wave- Echelle Spectrograph (UVES). length of ~ 950 nm. This limits a bit the overlap with
Table 1: Performance of the system; ‘good seeing’ R = 10 R = 13.5 R = 15 R = 17.4 was when the seeing was below 0.78?, while the Ensquared energy, 63 % 58 % – – ‘bad seeing’ was above 0.73? (DIMM measurements). good seeing The Strehl values and ensquared energy indicated Ensquared energy, 56 % 50 % 43 % 30 % are for K-band, taking into account the aberrations bad seeing introduced by the infrared test camera (82 %), and are therefore pessimistic. For a guidestar magnitude Best Strehl achieved 61 % 47 % 25 % (6 %) of R = 17.4 the value given for the Strehl ratio is only indicative: it is so low, that the concept of Strehl ratio starts loosing its meaning.
Figure 3: Left: A composite JHK false colour image of the Jovian Satellite Io. Io measures 3 600 km and was at a distance of 4.45 AU. A volcanic erup- tion is visible, so bright that its airy pattern ap- pears above the planet’s background. The apparent diameter of the disc is 1.1 arcsec. On the right a 3D-image in K-band of the binary star HD 105196
(mv = 8.3/ΔmK = 1.3) having a separation of 85 milli- arcsec.
The Messenger 124 – June 2006 Telescopes and Instrumentation
Probing Unexplored Territories with MUSE: a Second-Generation Instrument for the VLT
Roland Bacon1 Martin Roth 2 mat of today’s detectors, large fractions Svend-Marian Bauer 2 Joop Schaye 7 of the sky can be surveyed in depth with Petra Böhm 2 Geneviève Soucail 6 imagers. As far as spectroscopic follow- Didier Boudon1 Matthias Steinmetz 2 up is concerned, this is still a very time- Sylvie Brau-Nogué 6 Stefan Ströbele 4 consuming task, given the relatively small Patrick Caillier1 Remko Stuik7 multiplex capabilities available. Recent Lionel Capoani1 Peter Weilbacher 2 development of large multi-object spec- C. Marcella Carollo 3 Herve Wozniak1 trographs such as VIMOS at VLT (Le Fèvre Nicolas Champavert1 P. Tim de Zeeuw7 et al. 2003) or DEIMOS at Keck (Fabers Thierry Contini 6 et al. 2003) has somewhat improved the Eric Daguisé1 situation. However, the total number Didier Dallé1 1 CRAL – Observatoire de Lyon, France of sources in a typical imaging survey is Bernard Delabre 4 2 Astrophysikalisches Institut Potsdam, much larger than what is possible to ob- Julien Devriendt1 Germany serve with spectroscopy. The selection Stefan Dreizler 5 3 ETH Zürich, Institute of Astronomy, of sources is then mandatory. Usually the Jean-Pierre Dubois1 Zürich, Switzerland selection criterion is based on a series Michel Dupieux 6 4 ESO of multi-colour images and is intended to Jean-Pierre Dupin 6 5 Institute for Astrophysics Göttingen, select the appropriate spectral character- Eric Emsellem1 Germany istics of the population of the searched Pierre Ferruit1 6 LAOMP – Observatoire Midi-Pyrénées, objects. This incurs a direct cost in tele- Marijn Franx 7 Toulouse, France scope time since more than one expo- Gérard Gallou 6 7 Sterrewacht Leiden, the Netherlands sure must be made at each sky location. Joris Gerssen 2 As another disadvantage, the selection Bruno Guiderdoni1 process is never 100 % efficient, and thus Thomas Hahn 2 The Multi Unit Spectroscopic Explorer a fraction of time of the follow-up spec- Denni Hofmann 5 (MUSE) is a second-generation VLT troscopy is lost due to misidentifications. Aurélien Jarno1 panoramic integral-field spectrograph Andreas Kelz 2 presently under preliminary design The major weakness of this approach, Christof Koehler 5 study. MUSE has a field of 1 × 1 arcmin2 however, is probably not the relatively low Wolfram Kollatschny 5 sampled at 0.2 × 0.2 arcsec2 and is as- efficiency of the method, but the a priori Johan Kosmalski1 sisted by the VLT ground layer adaptive selection of targets. This pre-selection Florence Laurent1 optics ESO facility using four laser severely biases the spectrographic obser- Simon J. Lilly 3 guide stars. The simultaneous spectral vations and limits considerably the dis- Jean-Louis Lizon 4 range is 0.465–0.93 µm, at a resolution covery space. Magali Loupias1 of R ~ 3 000. MUSE couples the dis- Stéphanie Lynn1 covery potential of a large imaging de- Antonio Manescau 4 vice to the measuring capabilities of Imager and spectrograph Richard M. McDermid 7 a high-quality spectrograph, while tak- Christian Monstein 3 ing advantage of the increased spatial The ideal instrument is one which simul- Harals Nicklas 5 resolution provided by adaptive optics. taneously performs both imaging and Laurent Parès 6 MUSE has also a high spatial resolu- spectroscopy. The idea is to merge into Luca Pasquini 4 tion mode with 7.5 × 7.5 arcsec2 field of one instrument the best of the two capa- Emmanuel Pécontal 1 view sampled at 25 milli-arcsec. In this bilities: for imaging it is field of view and Arlette Pécontal-Rousset1 mode MUSE should be able to ob- high spatial resolution; and for spectrog- Roser Pello 6 tain diffraction-limited data cubes in the raphy it is high resolving power and large Chantal Petit1 0.6–0.93 µm wavelength range. spectral range. Jean-Pierre Picat 6 Emil Popow 2 Such an instrument will overcome the Andreas Quirrenbach 7 Imager or spectrograph? difficulty inherent to the classical method. Roland Reiss 4 Because there is no longer the need Edgar Renault1 Imagers and spectrographs are the most to pre-select the sources, one can even common tools of optical astronomers. detect objects that would not have been In most cases, astronomical observations found or pre-selected in the pre-imag- start with imaging surveys in order to find ing observations. In the most extreme the interesting targets and then switch case, such as objects with very faint con- to spectrographic observations in order tinuum but relatively bright emission lines, to study the physical and/or dynamical the objects can only be detected with properties of the selected object. Thanks this instrument, not with direct imaging to the excellent throughput and large for- techniques.
The Messenger 124 – June 2006 Telescopes and Instrumentation Bacon R. et al., Probing Unexplored Territories with MUSE
A simple computation shows that such Table 1: MUSE Observational Parameters pling from 0.2 arcsec to 0.025 arcsec. an ideal instrument will necessarily need The field of view is proportionally reduced a lot of detector pixels. For example con- Simultaneous spectral 0.465–0.93 µm to 7.5 × 7.5 arcsec2. The most signifi- sider a spatial field of view corresponding range cant change is in the AO optimisation and to a standard 2 048 × 4 096 pixel detector Resolving power 2 000 at 0.46 µm configuration (laser guide stars are moved 4000 at 0.93 µm and a wavelength range of 0.4–0.8 µm closer) and the tip/tilt, which is performed Wide-Field Mode with a spectral resolution of 3 000, which at IR wavelengths on either a natural Field of view 1 × 1 arcmin2 translate to 4 000 spectral pixels. The to- guide star within the field of view or the Spatial sampling 0.2 × 0.2 arcsec2 tal number of pixels is then 16 × 109. Giv- object itself. With such a configuration, Spatial resolution at 0.46 arcsec (AO) en that some optics are needed in front 0.75 µm (median seeing) 0.65 arcsec (non AO) the AO facility is expected to deliver a dif- of these pixels, one can immediately see AO condition of 70th percentile fraction-limited image with a Strehl ratio the feasibility problem. operation of 5 % (goal 10 %) at 0.75 µm. Sky coverage with AO 70% at galactic pole 99% at galactic equator
The Multi Unit Spectroscopic Explorer Limiting magnitude IAB = 25.0 (full Res) Science with the Wide-Field Mode in 80 h IAB = 26.7 (R = 180) –19 –1 –2 The Multi Unit Spectroscopic Explorer Limiting flux in 80 h 3.9 10 erg s cm MUSE has a broad range of astrophysical (MUSE) for the ESO/VLT telescope is a Narrow-Field Mode applications, ranging from the spectro- 2 major step towards this ideal instrument. Field of view 7.5 × 7.5 arcsec scopic monitoring of the Solar System’s 2 MUSE is being studied and built by a Spatial sampling 0.025 × 0.025 arcsec outer planets to very high-redshift gal- consortium consisting of six major Euro- Spatial resolution at 0.042 arcsec axies. We give in the following sections a 0.75 µm (median seeing) pean institutes, at Lyon (PI institute, CRAL, few examples of scientific applications Strehl ratio at 0.75 µm 5% (10% goal) France), Göttingen (IAG, Germany), that are considered to be important in- Limiting magnitude in 1 h R = 22.3 Potsdam (AIP, Germany), Leiden (NOVA, AB strument drivers. Limiting flux in 1 h 2.3 10–18 erg s–1 cm–2 Netherlands), Toulouse (LATT, France), –2 Limiting surface RAB = 17.3 arcsec Zurich (ETH, Switzerland) and ESO. It is brightness (mag) The most challenging scientific and tech- an integral-field spectrograph (or IFU) nical application, and the most important which combines large field of view, high ber of spectral pixels (4 000), resulting in driver for the instrument design, is the spatial resolution, medium resolving 360 million elements in the final data study of the progenitors of normal nearby power and large simultaneous spectral cubes. Such a large number of pixels is galaxies out to redshifts z > 6. These range. not feasible with a single piece of optics systems are extremely faint and can only and a single detector. MUSE is thus be found by their Lya emission. MUSE Nowadays, integral-field spectroscopy is composed of 24 identical modules, each will be able to detect these in large num- part of the panoply of modern tele- one consisting of an advanced slicer, a bers (~ 15 000) through a set of nested scopes. However, most of the currently spectrograph and a (4k)2 detector. A se- surveys of different area and depth (Fig- operating integral-field spectrographs ries of fore-optics and splitting and relay ure 1). The deepest survey will require have only a small field of view and are optics derotates and splits the square very long integration (80 hrs per field) to thus devoted to the detailed physical field of view into 24 subfields. These are reach a limiting flux of 3.9 × 10–19 erg study of single objects. Some multi-IFUs, placed on the Nasmyth platform between s–1 cm–2, a factor of 100 times better than like Giraffe at the VLT (Pasquini et al. the VLT Nasmyth focal plane and the what is currently achieved with narrow- 2002), have multiplex capabilities of a 24 IFU modules. AO correction will be per- band imaging. These surveys will simul- dozen objects, which increase their formed by the VLT deformable second- taneously address the following science efficiency. This however does not break ary mirror. Four sodium laser guide stars goals: the operational three steps (imaging, are used, plus a natural star for tip/tilt – Study of intrinsically faint galaxies at selection and spectrography) paradigm. correction. All guide stars are taken out- high redshift, including determination of side the scientific field of view in order their luminosity function and clustering MUSE has three operating modes: a to minimise the amount of scattered light, properties, wide-field mode which can work with and while the only additional optic located – Detection of Lya emission out to the without adaptive optics correction and a within the scientific field of view is a rev- epoch of reionisation, study of the narrow-field mode with high spatial reso- olutionary Na notch filter, reducing trans- cosmic web, and determination of the lution. The observational parameters are mission losses with respect to tradition- nature of reionisation, given in Table 1. al AO systems. This complex AO system – Study of the physics of Lyman break is part of the general VLT AO facility galaxies, including their winds and The total number of information ele- (Arsenault et al. 2006). The part specific feedback to the intergalactic medium, ments is given by the product of the num- to MUSE is called GALACSI. – Spatially resolved spectroscopy of ber of spaxels1 (90 000) with the num- luminous distant galaxies, including The MUSE narrow-field mode uses an lensed objects (Figure 2) 1 Spatial elements (to be distinguished from detector additional optical system inserted into the – Search of late-forming population III pixels). fore-optics to change the spatial sam- objects,
The Messenger 124 – June 2006 Figure 2: An HST-ACS image of the lensing cluster Abell 1689 (Broadhurst et al. 2005). This cluster is a prime candidate for strong lensing studies with MUSE, given its very large Einstein radius, and the Figure 1: Simulated MUSE deep field. Galaxies are large number of arcs identified. Broadhurst et al. coloured according to their apparent redshift. identified at least seven systems which were multiply
Galaxies detected by their continuum (IAB < 26.7 mag) imaged. The upper panel shows the full image, and/or by their Lya emission (Flux > 3.9 × 10–19 erg the lower panels show some of the strongly lensed s–1 cm–2) are shown. galaxies.
Lya 6.7
z
2.8 3.0 1 arcmin1
z
0.2 Cont 1 arcmin
– Study of active nuclei at intermediate and high redshifts, – Mapping of the growth of dark matter haloes, – Identification of very faint sources detected in other bands, and – Serendipitous discovery of new classes of objects. Multi-wavelength coverage of the same fields by MUSE, ALMA, and JWST will provide nearly all the measurements needed to answer the key questions of galaxy formation.
At lower redshifts, MUSE will provide ex- quisite two-dimensional maps of the kinematics and stellar populations of normal, starburst, interacting and active galaxies in all environments, probing sub-kiloparsec scales out to well beyond the Coma cluster. These will reveal the Science with the Narrow-Field Mode and beyond. However, observationally internal substructure, uncovering the fos- very little is known about this environ- sil record of their formation, and probe In contrast to the Wide-Field Mode, the ment, either in terms of stellar orbital the relationship between super mas- Narrow-Field mode science is dedicated structure or chemical enrichment history. sive black holes and their host galaxies to detailed studies of single objects at (Figure 3). very high spatial resolution. We give in the Young stellar objects: The key contribu- following a few examples. tion from MUSE will be both in spectral MUSE will enable massive spectroscopy grasp (covering key diagnostics of den- of the resolved stellar populations in The study of supermassive black holes: sity, temperature and ionisation) and the the nearest galaxies, outperforming cur- During galaxy mergers, supermassive ability to provide very high spatial reso- rent capabilities by factors of over 100. black holes sink to the bottom of the po- lution over a relatively large field of view. This will revolutionise our understanding tential well, forming binary systems This will allow the physical processes of stellar populations, provide a key which ‘scour out’ lower-density cores in involved in the formation and structure of complement to GAIA studies of the Gal- the central regions of the remnant. the jets to be investigated in detail. axy, and a preview of what will be pos- Such processes should leave detectable sible with an ELT (Figure 4). signatures in the environment of the Solar System: MUSE NFM would allow SMBH. Likewise, accretion of mass onto observations of various bodies within supermassive black holes should trigger our Solar System at a spatial resolution activity and feedback to the local regions approaching that of more costly space
The Messenger 124 – June 2006 Telescopes and Instrumentation Bacon R. et al., Probing Unexplored Territories with MUSE
Figure 3: Selection of nearby early-type galaxies observed with SAURON (de Zeeuw et al. 2002). Top row shows the reconstructed images, which are regular and smooth. The middle row shows the ve- locity field, and the bottom row shows the distri- Intensity bution of Mgb absorption strength. MUSE will be able to expand this pilot study at larger distance and in different cluster environments. Velocity b Mg
Figure 4: Left: Composite image of the southern spiral galaxy NGC 300, illustrating the power of massive spectroscopy with MUSE. The frames to the right are a narrowband [O iii] 5007 exposure (top), and a corresponding nearby continuum exposure (bottom), obtained with the NTT over a FOV of 2.2 × 2.2 arcmin2 (Soffner et al. 1996). MUSE will cover the same field in a total of four exposures. Unlike the narrowband imaging example, the MUSE data cube will provide full spectral information for each spatial element, with a huge discovery potential for massive stars, super bubbles, H ii regions, PNe, SNRs, novae – virtually the full inventory of the stellar and gaseous constituents of the galaxy.
missions. Applications are: monitoring – High stability and reliability over long pensates for the axial chromatism, which volcanic activity on the Galilean satellites, exposures then does not need to be corrected spectral monitoring of Titan’s atmos- – Maintain cost, mass and volume optically. This is a cost-effective solution, phere, global monitoring of the atmos- The 24 IFUs are central to MUSE. They avoiding the use of expensive optical pheres of Uranus and Neptune, inter- have been designed to achieve an ex- materials, e.g. CaF2. nal structure and composition of comets cellent image quality (85 % enclosed en- and mineralogical surface heterogene- ergy within 15 × 30 µm2 in the detector To maintain a high throughput (40 % for ities of asteroids. plane), and make use of innovative slicer the whole instrument) despite the rela- and spectrograph concepts. The slicer is tively large number of required surfaces, based on a two-mirror compact design, attention is paid to use state-of-the-art Opto-mechanical concept suitable for diamond machining (Figure 5 transmission and reflection coatings. and 6). Recent progress of the manufac- Detectors are 4k × 4k 15 µm deep deple- The opto-mechanical concept has to fulfil turing process has enabled high-preci- tion devices with improved quantum the following challenging requirements: sion metal surfacing with good surface efficiency in the red. Furthermore we will – Replication of modules at low cost in roughness (3 nm rms). Such mirrors are use new volume phase holographic gra- order to achieve the required number of now compatible with optical wavelength tings with a high efficiency over the large spatial and spectral elements. requirements and are much more cost (one octave) spectral range. – High throughput despite the required effective than other approaches for the number of optical surfaces large-scale production foreseen for MUSE. To simplify the interfaces between GAL- – High image quality in order to optimally The compact spectrograph design ACSI and MUSE, all AO components, use the image quality delivered by the achieves an excellent image quality over including the tip/tilt sensor, are mounted AO facility the large spectral bandwidth of MUSE. in the Nasmyth derotator. There is In this design, the tilt of the detector com- therefore a risk of misalignment of the AO
The Messenger 124 – June 2006 Figure 6: Breadboard slit (bottom) and pupil mirror array (top) in test at CRAL.
Figure 5: Each MUSE slicer consists of four stacks of 12 slit-mirror arrays (right side of the figure) and four stacks of 12 pupil-mirror arrays (left side). This gives a total of 2304 spherical mir- rors for the full instrument.
Figure 7: General view of MUSE at the VLT Nasmyth platform. reference system with respect to MUSE, Nasmyth platform of roughly 50 m3. This up with a highly modular character for the which is located on the platform. To mit- is bigger than every instrument that has assembly, maintenance and any opera- igate this risk and to maintain the optical been built so far for the VLT and will make tional exchange. axis within the tight tolerances required MUSE an impressive instrument (Figure 7 by the spatial performances and stability, and 8). With these dimensions, assem- a metrology system has been designed. bling and providing the necessary access Operations and data reduction It is a closed-loop system based on four to all the components is a challenge. reference light sources located in the The main instrument structure is de- Despite its impressive number of opto- fore-optics and imaged into the AO sys- signed as a single unit to fulfil the highly mechanical elements, MUSE will be easy tem. demanded stability of all optical compo- to operate. There are no moving parts in nents with respect to each other in order the 24 modules and the switch between The cryogenic system is based on pulse to maintain the superb image quality wide to narrow-field mode implies only tubes, which are compact and which given by GALACSI on long exposures. the addition of some optics within the avoid refilling 24 dewars with liquid nitro- fore-optics train. MUSE has only three gen. The accompanying compressors The latter is done with a complex optical operating modes: non-AO and AO wide are located outside the Nasmyth platform system that has to derotate and to split field mode, and AO narrow-field mode. on the telescope floor to avoid any pos- the observing field and to distribute and The three modes differ only by the pres- sible transmittance of vibrations onto the feed the spectrographic units with these ence of AO and the spatial sampling. In instrument. sub-fields. Despite its 24 spectrographs the wide-field non-AO mode, operations mounted into a monolithic structure, will be limited to the simple point-and- The instrument weight is approaching MUSE will act as a single instrument with shoot scheme. In the other modes, the eight metric tons in total and its size respect to the telescope and the AO sys- complexity is related to the operations of will fill basically the entire volume of the tem. Nevertheless, the instrument is set AO including the lasers. All modes share
The Messenger 124 – June 2006 Telescopes and Instrumentation Bacon R. et al., Probing Unexplored Territories with MUSE
the same spectroscopic configurations Figure 8: MUSE view (wavelength range and resolution). from the back of the Nasmyth platform. One can see the 24 spectro- On the other hand, with 1.6 Gb per single graph cameras and exposure, the data reduction is a chal- the cryogenic systems. lenge, not only because of this data vol- ume, but also because of its 3D char- acteristics. The handling of such large data cubes is not straightforward. As an example, one can mention the optimal summation of a series of data cubes ob- tained with AO and different atmos- pheric conditions. This is intrinsically a 4- dimensional problem because the AO- delivered PSF changes with time, location within the field of view, and wavelength.
Project status
The project is currently in its preliminary design phase. In July 2006, the opti- cal preliminary design review will be the starting point for the manufacturing of – It will be the first spectrograph opti- Acknowledgements a complete breadboard consisting of a mised to work with very long integration MUSE is funded by ESO and the following funding slicer, a spectrograph and a detector, times and to reach extremely faint emis- agencies and Universities: while the full preliminary design review is sion-line detection. – The Institut National des Sciences de l’Univers scheduled for early 2007. Results of the (INSU) of CNRS, the University Claude Bernard breadboard will be analysed for the final MUSE will thus be able to discover ob- Lyon I, the University Paul Sabatier Toulouse III and the Ministère de la Recherche et de la Technologie design review in July 2008. Manufac- jects that have measurable emission for the French participation turing, assembly and integration will then lines, but with a continuum that is too – The Verbundforschung of the Federal Ministery for take place up to mid 2011. First light faint to be detected in broad-band imag- Education and Research (BMBF), managed by is scheduled on Paranal in early 2012. ing. For example, the deepest broad- PT-DESY, by the Astrophysical Institut Potsdam and by the University of Göttingen for the German band imaging available today is the HST participation Ultra Deep Field (UDF) with IAB < 29. – The Netherlands Research School for Astronomy Conclusions According to CDM simulations, however, (NOVA) and the Netherlands Organisation for Sci- only 15 % of MUSE high-z Lya emitters entific Research (NOW) for the Dutch participation – The Swiss Federal Institute of Technology Zürich Astronomy is to a significant degree still (z > 5.5) will have a continuum bright (ETH) and the Swiss National Science Foundation driven by unexpected discovery (e.g. dark enough to be detected in the UDF. MUSE through the FINES fund for the Swiss participation matter and dark energy). These discov- is also the only instrument capable of A dedicated integration hall for MUSE will be build at eries are often made by pushing the limit detecting faint diffuse ionised gas, like CRAL. This building is funded by the Région Rhône- Alpes, the CNRS, the city of Lyon, the Ministère de la of observations with the most powerful extended halos or filaments. Finally, ob- Recherche et de la Technologie, the University telescopes and/or opening a new area of jects with unusual spectral features Claude-Bernard Lyon I, the Grand Lyon, the town of instrumental parameter space. MUSE is should also be detected by MUSE, what- Saint-Genis-Laval and the Rhône department. designed to push the VLT to its limit and ever their broad-band magnitude and MUSE public web site: http://muse.univ-lyon1.fr to open a new parameter space area in colours are. The unprecedented capabili- sensitivity, spatial resolution, field of view ties of MUSE should also lead to dis- and simultaneous spectral coverage. We coveries far away from our present ex- References are convinced that it fulfils all the required pectations. Arsenault R. et al. 2006, The Messenger 123, 6 conditions to have a large potential of Broadhuust T. et al. 2005, ApJ 621, 53 discoveries: In many aspects, MUSE is a precursor of Fabers S. et al. 2003, SPIE 4841, 1657 – It will be the first spectrograph that can future ELT instrumentation. For exam- Le Fèvre O. et al. 2003, SPIE 4841, 1670 blindly observe a large volume of space, ple, manufacturing, integration and main- Pasquini L. et al. 2002, The Messenger 110, 1 Soffner T. et al. 1996, A&A 306, 9 without any imaging pre-selection. tenance of a large number of identical, de Zeeuw P. T. et al. 2002, MNRAS 329, 513 – It will be the first optical AO-assisted high-performance optical systems at low IFU working at improved spatial re- cost and on reasonable time scale will solution in most atmospheric conditions be a critical aspect for most of the ELT in- with large sky coverage. struments.
10 The Messenger 124 – June 2006 Telescopes and Instrumentation
New, Efficient High-Resolution Red VPH Grisms in VIMOS
Gianni Marconi, Stefano Bagnulo, anti-reflection coated, 4k × 2k pixel CCD. Table 1: VPHG HRred grism characteristics. Jean-Louis Lizon, Bernard Buzzoni, VIMOS operates in three different modes: Hans Dekker, Sandro D’Odorico, Imaging (IMG), Multi-Object Spectros- Wavelength range 0.50–1.05 micron Carlo Izzo, Burkhard Wolff (ESO) copy (MOS), and with Integral Field Unit Spectral resolution R ~ 2 500 (IFU). For a summary of the instrument Dispersion ~ 0.6 Ångstrom/pixel capability and performance, see http:// VIMOS is the visible (360 to 1000 nm) www.eso.org/instruments/vimos/ One of the final prisms and grism optical wide-field imager and multi-object spec- assemblies is shown in Figure 1; the same trograph mounted on the Nasmyth focus One of the High-Resolution Red grisms element as hosted into the new mechani- B of Melipal (UT3) (Le Fèvre et al. 2003). (600 grooves/mm) was damaged during cal mount is shown in Figure 2. This new The instrument is comprised of four iden- the instrument testing phase. From the mounting includes an on-board alignment tical arms each with a field of view of beginning of operation in 2003, observa- system which reduces the time needed 7; × 8; with a 0.205? pixel size and a gap tions in this mode had to be executed to realign the grisms in case of dismount- between each quadrant of ~ 2;. Each using a HRorange grism in one of the ing or earthquake events to a few minutes. arm is equipped with six grisms providing channels. Coupled with the relatively low a spectral resolution range from ~ 200– efficiency intrinsic to the old grisms, The comparison of the old versus new 2500 and with an EEV 44-82, thinned, this mismatch was a strong limitation to grism efficiency curves as measured the performance of the instrument in in the ESO optical lab is shown in Fig- this particular setup. In September 2005 ure 3; the wavelength range 0.6–0.9 mi- Figure 1: Prisms and grating optical the HR grisms were replaced by cron corresponds to a slit at the centre elements glued together. red a new set of Volume Phase Holographic of the field. The response of the new VPH (VPH) grisms offering a superior efficiency grisms with VIMOS was measured by ob- while maintaining the same spectral re- serving spectrophotometric standard solution. The VPH grisms were manufac- stars on different photometric nights. The tured by CSL and their operating charac- global efficiencies of the UT3+VIMOS+ teristics are given in Table 1. grism with both the old and the new
VPHG HRred, as provided by the ESO- The definition of requirements, the VPH VIMOS pipeline, are shown in Figure 4. specifications, the procurement and A notable improvement (~ 40–70 %, de- the gluing of the prisms and the VPHGs pending on wavelength) has been ob- were done by the Optical Instrumenta- tained in the full spectral range covered tion Department. The mounting design, by the grisms. integration and testing by the Integra- tion Department. Commissioning and Reference characterisation were carried out by the Operation Staff in Paranal and VIMOS- Le Fèvre O. et al. 2003, SPIE 4841, 1670 assigned staff in the Data Management Division. Figure 4: The comparison between the global effi- Figure 3: The efficiency curve of the old grism (black ciency (telescope+instrument+grism) as measured Figure 2: The VPH grism as hosted line) and the new one (red line) as measured in the on sky by using the same spectrophotometric stand- inside the new mounting. laboratory. ard star; old grism (black line) new grism (red line).
1.0
New VPHG grism New VPH grism Old grism Old grism 0.2 0.8 ) rism +G Ins
0.6 + 0.15 el (T
ciency fi Ef ciency fi
0.4 l Ef ta 0.1 To
0.2
0.05 4000 6000 8000 10000 6500 7000 7500 8000 8500 Wavelength (Ångstrom) Wavelength (Ångstrom)
The Messenger 124 – June 2006 11 Telescopes and Instrumentation
The Atacama Pathfinder EXperiment
Rolf Güsten1 Lars-Åke Nyman 2 Karl Menten1 Catherine Cesarsky 2 Roy S. Booth 3, 4 Peter Schilke1
1 Max-Planck-Institut für Radioastro- nomie, Bonn, Germany 2 ESO 3 Onsala Space Observatory, Onsala, Sweden 4 now at Hartebeesthoek Radio Astron- omy Observatory, South Africa
APEX, the Atacama Pathfinder Experi- ment, is operational on Llano de Chaj- nantor, on what is considered one of the world’s best sites for submillimetre astronomy. With its large primary re- flector of 12 m diameter, carefully ad- justed to a surface smoothness of only 17−18 µm r.m.s, APEX will allow obser- vations up to 200 µm, through all at- mospheric submm windows accessible from the ground. Scientific opportuni- ties to explore the ‘cold universe’ are discussed, and first scientific results are presented.
Go Atacama! 1 A brief project history 0.3 mm pwv 0.6 mm pwv Because submillimetre radiation from 1.0 mm pwv By the mid 1990s, the astronomical rich- ) space is heavily absorbed by water te ness of the submillimetre wavelength si vapour in the Earth’s atmosphere, APEX X range had been demonstrated by the PE (A is located at an altitude of 5100 metres early successes of the 15-m James Clerk in the high Atacama desert on the Chaj- 0.5 Maxwell telescope and the Caltech nantor plains, 50 km east of San Pedro Submillimeter Observatory 10.4-m tele- ansmission
de Atacama in northern Chile. The ALMA Tr scope, both operating on the 4 000-m site characterisation, covering the years high Mauna Kea on Hawaii. At that time, 1995 to 2004, has shown that the loca- in North America, Europe, and Japan tion is one of the driest places on Earth: 0 plans for a large millimetre interferometer 500 1000 1500 the 50 (25) % quartile of the precipitable Frequency (GHz) array were made and extensive site test- water column is 1.0 (0.6) mm, respec- ing campaigns were undertaken. In the tively. During the Chilean winter months Figure 2: Zenith transmission of the atmosphere course of these, the 5 100-m high Llano (June through September), for an ap- above Llano de Chajnantor at submillimeter wave- de Chajnantor was identified as possibly lengths. Using data from the ALMA site charac- preciable fraction of the time conditions terisation, we calculate the 50 and 25 % quartile the best accessible site on Earth for are better than 0.3 mm pwv – exceptional columns of precipitable water to 1.0 and 0.6 mm, submillimetre astronomy, outside of conditions for which the supra-THz at- respectively – excluding data taken during the Antarctica. In fact, the weather statistics mospheric windows become transparent Bolivian winter months (day numbers 15–90). The for that site looked so good that the initial dark blue figure corresponds to 0.3 mm pwv, a for dedicated experiments (see Figure 2). rare, but not uncommon event that opens up the interferometer concept was extended supra-THz windows. and, despite its name, the Atacama Large Millimeter Array (ALMA) was planned to cover all the millimetre and submillimetre windows with good transmission to the ground.
12 The Messenger 124 – June 2006 Photo: A. Lundgren, ESO
Convinced of the quality of the Chajnan- the high site started in spring 2003; com- Figure 1: Panoramic view of the ALMA site, Llano de tor site, Karl Menten persuaded the Max- missioning began in spring 2004. After Chajnantor, taken from Cerro Chico. The APEX telescope is seen to the left, and our next neighbour, Planck-Society to provide funding to successful verification of the performance the CBI experiment, to the right. The ALMA AOS acquire a copy of one of the ALMA proto- of the telescope to specifications, the technical building (now under construction) and the type antennas (at that time three proto- facility was inaugurated on 25 September compact array configuration will be located in the types were planned) with as early as pos- 2005. With operational readiness the re- centre of the picture. sible deployment to Chajnantor – as a sponsibility for operation of the facility pathfinder for ALMA. ESO and the Onsala was entrusted to ESO, and responsibility on Chajnantor as well as in Sequitor. Duty Space Observatory (OSO) appeared was transferred from Rolf Güsten (Pro- staff sleep in the Sequitor base. The tele- as natural partners, since they had been ject Manager since spring 2004, during scope can be controlled remotely from operating the highly successful 15-m the commissioning phase) to the Station Sequitor through a 36 Mbit/s microwave Swedish-ESO Submillimetre Telescope Manager Lars-Åke Nyman. link and the Sequitor base has a 2 Mbit/s (SEST, Booth et al. 1987) since 1987 on connection to the outside world. Chaj- the lower altitude La Silla. The new ESO nantor is accessed either by the interna- Director General, Catherine Cesarsky, Operation of the Facility tional highway to Argentina, the Paso and Onsala Space Observatory Director Jama road (paved), for the first 60 km, Roy Booth welcomed the idea enthusias- The unique observing opportunities come followed by a 15-km dirt road, or through tically – the Atacama Pathfinder EXperi- with the costs of demanding logistics the ALMA road, which is now being con- ment was born. required to operate a frontier science ob- structed. servatory at a place as remote as Llano Immediately after the Memorandum-of- de Chajnantor. The telescope is operated The telescope is situated on Chajnan- Understanding between the partners was from the APEX base in Sequitor in tor about 2 km north of the newly con- signed on 02 July 2001, MPIfR con- San Pedro de Atacama at an altitude of structed ALMA AOS building and array tracted the design and construction of 2 440 m. However, it was essential that centre. The area includes the telescope the telescope to VERTEX Antennen- infrastructure to support operations and and a set of containers consisting of technik GmbH, Germany. Construction at maintenance of the telescope was built a control room, emergency dormitory,
The Messenger 124 – June 2006 13 Telescopes and Instrumentation Güsten R. et al., The Atacama Pathfinder EXperiment
Figure 3: The APEX control room in the Sequitor base, from which Claudio Agurto operates the telescope (low- er left). The radio link transmitters are visible on top of the building. To the left, the laboratory wing is seen, with our open air meeting room. laboratory, kitchen, storage and sanitary facilities. The control room and dormitory are oxygenated to a level of 29 %, which makes it reasonably comfortable to work inside. For outside work the staff
use portable oxygen systems. Electrical Photos: A. Lundgren, ESO power is provided through two genera- tors, each producing 450 kVA at sea level (downgraded to about half of that at 5100 m). Telephone connections and net- work are provided through the microwave link, and there is radio communications equipment for contact between the pick- up trucks, Chajnantor and Sequitor. Work at the high altitude is governed by strict safety rules; access to the site requires authorisation by the Station Manager.
The Sequitor base is situated about 6 km south of the centre of San Pedro de Atacama on 2.2 ha of land. It is located in the oasis of San Pedro with trees and vegetation, and access to irrigation water every three weeks. The buildings are made of adobe and follow the local style of construction. There is a building con- taining offices, laboratories and a control room, as well as 17 dormitories, a cafe- teria, a meeting/recreation building and storage. Power is provided through two generators, water is provided from San Pedro, hot water is produced through a combined solar/electrical heating system and there is a sewage treatment plant as well as a gasoline station. Figure 4: APEX at sun- set with Cerro Chajnan- tor in the background. The staff of 25, including astronomers, operators, engineers, technicians and maintenance personnel, is contracted to The Telescope INVAR cone, which is attached to the top ESO. The APEX staff must deal with of the Cassegrain cabin. The adjustable the many kinds of logistics activities of a The APEX telescope is a modified copy panels, manufactured to a surface ac- remote site, including trips and trans- of the VERTEX ALMA prototype, custom- curacy of 8 µm rms, have been chemical- fers for staff and visitors, transport of ma- ised for stand-alone (single-dish) op- ly etched to scatter solar radiation, allow- terials to and from Santiago and abroad, eration. Two additional Nasmyth cabins ing daytime observations. deliveries of diesel fuel for the generators, for heterodyne receivers and two large catering and cleaning services, infra- instrument containers for supplemen- The aluminium secondary reflector, sup- structure maintenance and truck mainte- tary equipment (such as spectrometers, ported by CFRP quadripod legs, provides nance (APEX operates five pick-up trucks). synthesizers, compressors and chillers) a field-of-view suitable for wide-field bo- add to a total mass of the modified anten- lometer arrays in the Cassegrain cabin. APEX is part of the local community of na of ~ 125 t. For operation (of basically the heterodyne Sequitor and San Pedro de Atacama, receivers) in the Nasmyth cabins, the and participates in local activities and The telescope is a Cassegrain system telescope waist from the secondary is contributes funds for educational, cultural with a parabolic main reflector, on an alt- transformed (through the elevation tube) and community projects. az mount. The 12-m-diameter reflector, by refocusing optics into the Nasmyth consisting of 264 aluminium panels in waists. The tertiary mirror package is on a 8 rings, is mounted on a carbon fibre re- rotary support to select between the two inforced plastic (CFRP) back-up struc- Nasmyth foci and to clear the optical path ture of 24 sandwich shell segments. The for the bolometer pick-up mirror (on the back-up structure is supported by an floor of the Cassegrain cabin).
14 The Messenger 124 – June 2006 Figure 5: Adjustment of the surface. 1320 positioners on in total 264 alu- minium panels were adjusted with a few µm accuracy. The small images show APEX engineer Juan Fluxa riding the cherry picker, and Leo Vanzi with Jorge Corante in the cage. Striving toward the perfect telescope
The coupling efficiency of a radio tele- scope to an astronomical source is ba- sically controlled by the surface smooth- ness e of its parabolic reflector: the Photos: R.Güsten, MPIfR classical Ruze formula describes the loss of efficiency with wavelength l as an exponential decrease ∝ exp(–(4π e/l)2), i.e. for e = l/15 the antenna coupling effi- ciency has decreased to half its maxi- mum already. In order to operate with high efficiency in the last of the classical atmospheric windows (around 300 µm wavelength, see Figure 2), the specifica- tions for the APEX require for a surface smoothness of better than 20 µm rms. This requires that, over the 12-m diameter of the main dish, the deviation from the perfect parabola has to be less than one fifth of the average thickness of a human hair – a rather challenging requirement on the manufacturing, assembly and ad- justment of the antenna.
After assembly, the main reflector was pre-aligned by VERTEX by means of op- tical photogrammetry to 35–40 µm rms surface accuracy. From there on the APEX holography team performed near- field holography with a 92.4 GHz trans- mitter located near the summit of Cerro Chajnantor, at an elevation angle of 13 deg. During three holography sessions (May and June 2004, April 2005), in an iterative process, phase residuals were measured and converted to surface error maps which were then used to correct for panel-to-panel misalignments and panel flexures. The manual adjustment of the (maximally) 1320 vertical adjuster ele- ments typically took a full workday, de- pending on the environmental conditions, with teams working in shifts (Figure 5). In April 2005, the surface was finally set and verified to an excellent 15 µm rms smooth- ness towards the transmitter (Figure 6). Because of gravitational deformations the performance of the antenna would rapidly degrade towards higher elevations. Therefore the finite-element model of the APEX dish was used to pre-load and thus optimise the surface settings for ele- vations that will actually be used for astronomical observations. The effective surface smoothness for the elevation range 30–80 deg, calculated to 17–18 µm, is confirmed by carefully calibrated measurements of the telescope’s cou-
The Messenger 124 – June 2006 15 Telescopes and Instrumentation Güsten R. et al., The Atacama Pathfinder EXperiment
pling efficiencies to astronomical sources Figure 6: The surface error pattern (planets). This makes APEX a superb of the APEX main reflector after the final (April 2005) holography telescope with performance well within session. The surface smoothness is 5 20 specifications that allows observations 14.7 µm rms (Güsten et al. 2006). ] µm into the supra-THz windows. [
parabola Science with APEX l 0
0 idea
As its name implies, APEX is a pathfinder om fr for other (sub)millimetre wavelength n atio missions, most directly for ALMA. This vi giant array of 50 12-m antennas sepa- De –5 rated by baselines up to 14 km, will also –20 be located on Llano de Chajnantor (Fig- ure 1) and is expected to start operation in 2012 (www.eso.org/projects/alma). –5 0 5 There are great complementarities to the Radius [m] Herschel Satellite and the Stratospheric Observatory for Infrared Astronomy quencies are shifted to the millimetre In a concerted effort with the IRAM 30-m (SOFIA), whose instruments will reach to range, but we know very little about the telescope, APEX has identified for the higher frequencies into the far-infrared very same transitions in nearby star- first time CF+ (fluoromethylidynium) in wavelength range not accessible from burst and merger galaxies. Particularly space. While its two lowest energy (and the ground. Towards longer wavelengths, the CHAMP+ heterodyne array will rem- lowest frequency) spectral lines were APEX picks up where the wavelength edy this imbalance. discovered with the former, APEX coverage of, e.g., the IRAM 30-m tele- clinched the identification with a third line. scope on Pico Veleta (Spain) ends. To- Early results from the first months of sci- This interesting molecule exists in an gether, the latter two instruments cover ence observations since operation readi- UV exposed molecular interface region all atmospheric windows observable from ness will be published soon in a special where the hot stars that excite the the ground between 0.2 and 4 mm with issue of Astronomy & Astrophysics Let- famous Orion Nebula also provide the comparable angular resolution (the half- ters. Here we highlight a few examples ionising radiation. Our observations power beamwidth of the 30-m antenna to demonstrate APEX’s immediate impact indicate that models of the chemistry of at the frequency of the CO(2–1) transition, on different fields of astronomy. fluorine-bearing molecules are realistic ~ 11?, compares nicely with the 9? resolv- and that these molecules can be used to ing power of APEX observations of warm probe interstellar clouds. They thus open CO(6–5) at 690 GHz). APEX detects a new molecular ion a new chapter in interstellar chemistry.
What does APEX observe? Mostly the More than 120 different molecules are cold and cool universe, through radiation known in the interstellar medium, about APEX reveals the nature of the BHR71 from molecules and dust. Molecular lines 10 % of them positively charged ions. outflow in the submillimetre range sample warmer Most of these molecules contain hydro- and denser gas than millimetre lines, so gen, oxygen, carbon, and nitrogen, It is commonly believed that highly- the formation of stars and galaxies and the four most abundant elements. A few collimated outflows are the first stage in the astrochemistry associated with these molecules containing silicon, sulfur, outflow evolution, and their study is events are central work areas for APEX. phosphorus and one even containing iron thus central to understand the interaction Molecular cores show very line-rich spec- have been found as well. However, only of the jet with the surrounding cloud. tra in the submillimetre range, the analy- two halogen-bearing molecules had been BHR71, a small Bok globule at 200 pc sis of which gives insight into the ignition known to exist in the interstellar medium: distance, harbours a beautiful example of phase of, particularly massive, stars. HCl and HF. HF, the main reservoir of such a highly collimated outflow. This Studying the submillimetre region is also interstellar fluorine, unfortunately is im- outflow is powered by a young low-mass crucial for understanding the feedback possible to observe from the ground but protostar, IRS1, belonging to a binary of newly born stars, through outflows and was detected with the Infrared Space system. Submm observations with APEX the creation of photon dominated re- Observatory by a team led by David of the CO(3–2) emission have confirmed gions. APEX will make particularly valua- Neufeld (Johns Hopkins University) that the existence of a second fainter and ble contributions to the study of galaxies, included APEX project scientist Peter more compact bipolar outflow, associ- where we are faced with the somewhat Schilke. Neufeld and colleagues recently ated with the other protostar of the binary paradoxical situation that the high-J (sub- put fluorine chemistry to closer scrutiny system (Parise et al. 2006). Tempera- millimetre) CO lines are well observed in and predicted CF+ to be the second most ture enhancements in the lobes of the highly redshifted objects, since the fre- abundant F-containing species. extended outflow are constrained by
16 The Messenger 124 – June 2006 Figure 7: HST image of the Orion neb- Figure 8: CO(3-2) map of the BHR71 ula. Towards the so-called Orion outflow. The colour scale represents ‘bar’ interface region APEX, together the integrated intensity over the whole with the IRAM 30-m telescope, velocity range of the IRS1 outflow. have detected a new ion molecule: Red and blue contours mark the inte- CF+ (Neufeld et al. 2006). Credit: grated intensities of the two lobes of NASA, C. R. O’Dell and S. K. Wong the outflow powered by IRS2 (Parise et (Rice University). al. 2006).
CF+ APEX J = 3–2 0.1
0 200
) 0.15 IRAM 30-m 100 0.1 J = 2–1
mperature (K 0.05 Te nna
te 0
An 0 0.04 IRAM 30-m J = 1–0 0.02 50 0
– 0.02 – 20 0 20 40 LSR Velocity (km s–1) –200
0 100 50 0 –50 –100
observations of high-energy lines of methanol. The authors derive tempera- 20 tures between 30 and 50 K, with den- sities ~ 105 cm–3. The small outflows ap- pear to be even warmer (up to 300 K). 0
–20 APEX goes extragalactic from the beginning 20 0 –20
The first extragalactic object at which APEX was pointed during its commis- sioning was NGC 253, which is consid- ered – with M82 – the archetypical nu- clear starburst galaxy. Because of its proximity, less than 10 million light years away in the southern constellation of Sculptor, APEX can spatially resolve its central circumnuclear gas layer. In Fig- ure 9 we display the emission of the CO J = 4–3 rotational transition (at a wave- length of 650 µm), superimposed on an NGC 253 optical image of the galaxy. Mapping different CO and atomic carbon lines al- Figure 9: Distribution of warm carbon lows studies of the density and tem- monoxide, as measured with APEX in its J = 4–3 rotational transition at perature of the gas in this interesting en- 461 GHz (Güsten et al. 2006), super- vironment. By modelling the excitation imposed on an optical image of of CO(4–3) and CO(7–6), we derive a ki- NGC 253. Spectra have been sampled netic temperature of 60 K and H density at half beam spacing (the beam 2 of APEX at this frequency is 13.3?). of ~ 104 cm–3 for the central gas layer. The submm rotational transitions of CO are shown to be the main cooling lines of the warm dense interstellar gas, peak- ing at J = 6–5 for the central 250 pc of NGC 253.
The Messenger 124 – June 2006 17 Telescopes and Instrumentation
These very first observations of a nearby Soon the first array receivers will be sion form found in the web pages, which starburst nucleus reveal the potential of commissioned: LABOCA, the 870 µm includes all information necessary for the APEX in constraining the gas excitation in 295 pixel facility bolometer camera, APEX staff to perform the observations. these nuclei. With broader band spec- is scheduled for June this year, and later The APEX raw data are stored in MBFits, trometers and the chopping secondary in August the Champ+ 2 × 7 pixel heter- the calibrated data in CLASS format. coming soon, and given the exceptional odyne array of the MPIfR will be com- ESO and Swedish data are transferred to observing conditions at the site, the missioned. In December OSO will deliver the ESO archive, and the release of data impact of this facility on extragalactic as- a suite of single pixel facility receivers follow the ESO archive rules. tronomy will be significant. covering the 210–500 GHz frequency range. Acknowledgements Instruments for APEX We thank the APEX staff and our teams at the home Observing with APEX institutes, whose outstanding support during the In parallel to the construction and com- build-up and commissioning phase has made missioning of the APEX, a demanding The observing time will be shared in pro- this project become reality on a compressed sched- cutting-edge technology programme has portion to the partner’s investments (45 % ule. We acknowledge with pleasure the support from Dave Morris and Albert Greve (both retired from been launched to provide the best pos- MPIfR, 24 % ESO, and 21 % OSO), with IRAM), and Nimesh Patel and T. K. Sridharan (CfA) sible detectors for this outstanding facil- 10 % allocated to Chile as host nation. for the holography of the telescope. ity. For its first observations, APEX was On the ESO side, APEX proposals are re- equipped with state-of-the-art submm viewed by the ESO OPC and deadlines References receivers developed by MPIfR’s Division follow the normal ESO deadlines for pro- for Submm Technology (FLASH I and II, posal submission. The APEX web pages Booth R., de Jonge M., Shaver P. 1987, Heyminck et al. 2006, with new technol- (www.apex-telescope.org) include tech- The Messenger 48, 2 ogy Fast-Fourier-Transform spectrom- nical descriptions of the system and ob- Güsten R. et al. 2006, A&A Letters (in press) Güsten R. et al. 2006, A&A Letters (in press) eters, Klein et al. 2006) and with a first serving time calculators. The observa- Heyminck S. et al. 2006, A&A Letters (in press) facility receiver (working in the 345 GHz tions are done in service mode, mainly Klein B. et al. 2006, A&A Letters (in press) atmospheric window) build at Chalmers during night-time. The Principal Investiga- Neufeld D. et al. 2006, A&A Letters (in press) University (Risacher et al. 2006). tors are asked to fill in a project submis- Parise B. et al. 2006, A&A Letters (in press) Risacher C. et al. 2006, A&A Letters (in press)
ALMA News
Tom Wilson (ESO)
ESO has selected Dr. Paola Andreani as the ARC Manager for ESO. Dr. Andreani will begin work at ESO Garching on 1 June 2006. Dr. Andreani is presently an Associate Astronomer at the Astronomi- cal Observatory of Trieste, a part of INAF. Dr. Andreani is also a Co-I of Herschel/ PACS and the local Project Manager of Herschel/SPIRE. She has been a working group manager of the Italian Herschel community, participating in the Herschel GTO process. Dr. Andreani is a well- known researcher in the field of extraga- lactic astronomy, and has carried out significant work on the Sunyaev-Zeldovich effect using the SEST. Dr. Paola Andreani
18 The Messenger 124 – June 2006 Telescopes and Instrumentation
The 2006 SPIE Symposium on Astronomical Telescopes and Instrumentation – Observing the Universe from Ground and Space
Alan Moorwood (ESO) – a special invited session featuring the conference based programme to facilitate best student papers this more efficiently. – tours of the University of Central Florida The most recent of these biennial SPIE – an exhibit featuring a full-scale model of In the first keynote plenary talk titled (The International Society for Optical the James Webb Space Telescope “Challenges for Astronomy and Astrophys- Engineering) Symposia was held from – 68 industrial and other exhibits – includ- ics in a Changing Budget Environment”, 24–31 May in the Orlando World Center ing the ESO stand shown in Figure 1 Garth Illingworth illustrated the variety Marriott Resort & Convention Center in and strength of the current US Space Florida, USA. Over the last decade, these The main conferences listed above cov- Science programme but then drew atten- meetings have grown to become the ered space telescopes and instruments tion to its anticipated reduction in the main forum for presenting and discussing sensitive over the full gamma ray to radio future due to the decline of the NASA all aspects of ground-based, airborne wave range, including overview talks budget expected following completion of and space telescopes and their instru- on the NASA and ESA programmes; the JWST. Of particular interest to many mentation, including associated ad- ground-based and airborne telescopes people was his list of estimated full-cycle vances in technology, software, opera- again covering all wavelengths and in- costs, including operations, for several tions and even astronomical results. As cluding ALMA and future extremely large flagship missions which ranged from a consequence the meetings are large telescopes (ELTs); ground-based and 9 billion dollars for HST down to ~ 2 bil- and well attended by people at all levels airborne instrumentation with invited lion for the airborne observatory SOFIA, in the process of initiating, approving, overview talks on the instrumentation at recently slated for possible cancellation implementing and operating astronomical all the major observatories; interferom- by NASA. Nevertheless, Garth made a projects and facilities. This year there etry; observatory operations; adaptive strong case for retaining the concept of were ~ 1700 registered participants who optics; opto-mechanical technologies; flagship missions rather than just trying presented ~ 1600 papers and posters software and control and detectors. to increase the number of smaller ones. in the following 12 parallel conferences Maybe he also put the current $ 4.5 bil- which formed the heart of the meeting. ESO staff and their achievements were lion cost of JWST in perspective for some very much in evidence in essentially people? – Space Telescopes and Instrumentation all the conferences dealing with ground- I: Optical, Infrared and Millimetre based topics. Everybody also seemed The second plenary talk was devoted to a – Space Telescopes and Instrumentation to benefit from learning what the others less political but currently hot scientific II: Ultraviolet to Gamma Ray are doing from the highest level over- topic “The Central Black Hole and Nucle- – Ground-based and Airborne Tele- views down to the most detailed ex- ar Star Cluster of the Galaxy” which was scopes changes of technical details. I don’t know delivered by Reinhard Genzel from the – Advances in Stellar Interferometry of any other such possibility for hear- MPE in Garching who presented a daz- – Ground-based and Airborne Instrumen- ing so many top-level talks covering such zling collection of recent VLT and other tation for Astronomy a range of topics in so short a time. Un- data made possible by developments in – Observatory Operations: Strategies, fortunately, with so many parallel ac- ground-based adaptive optics and inte- Processes and Systems tivities, considerable time is spent in navi- gral-field infrared spectroscopy. These – Modelling, Systems Engineering and gating the programme and, again, the have now established the presence and Project Management for Astronomy II organisers have vowed next time to try mass of the black hole at the centre of – Advances in Adaptive Optics and make a chronological as well as the Milky Way beyond reasonable doubt – Opto-Mechanical Technologies for Astronomy – Advanced Software and Control for Astronomy – Millimetre and Submillimetre Detectors and Instrumentation for Astronomy III – High Energy, Optical and Infrared De- Photo: E. Janssen, ESO tectors for Astronomy II
In addition were – four invited keynote plenary talks – a plenary conference of invited talks on the search for extrasolar planets – six specialist workshops/technical meetings/panel discussions – nine courses teaching special aspects of optics, detectors and software Figure 1: Visitors to the – two major interactive poster sessions ESO stand – another first at the Orlando 2006 – two networking receptions meeting.
The Messenger 124 – June 2006 19 Telescopes and Instrumentation Moorwood A., The 2006 SPIE Symposium
and have revealed and partially charac- Figure 2: Catherine terised its associated infrared flares – Cesarsky, Director Gen- eral of ESO, delivering which can provide further insight into its her plenary talk on properties (e.g rotation) – but appear to “Astronomy in Europe: have increased the mystery of the origin Status and Prospects” of its surprisingly young surrounding star Photo: E. Janssen, ESO to a packed audience. cluster.
The next plenary talk, on “Astronomy in Europe: Status and Prospects”, was delivered by Catherine Cesarsky, Director General of ESO, whose main theme was the growth of European astronomy over the last few decades and the breadth and depth which have already been achieved by the combination of the ESO, ESA and national programmes. She also stressed 3.6-m telescope on La Silla (see ESO visible and infrared sensors, CCD and Europe’s commitment to the future, in- Press Release 18/06). CMOS imaging sensors and applications cluding the building of an Extremely Large and scalable frameworks for observatory Telescope on the ground. The final ple- Other papers of particular European inter- software infrastructure. As far as I can nary talk was on “Novel Technology for est included those on the contributions judge, all seemed well attended whenever Optical and Infrared Astronomy” in which to be expected in the future from astrom- I passed by on the way to somewhere Colin Cunningham of the UKATC in Edin- etry with the VLTI (Didier Queloz); imaging else. burgh took us on a tour of the latest ideas with future ELTs (Roberto Gilmozzi); re- which may transform future ground- sults and plans for transit/eclipse obser- The large number of attendees and pa- based instrumentation including robotic vations with MOST, COROT and Kepler pers plus its seven-day duration reflects and other smart focal-plane systems, (Jaymie Matthews) plus the capabilities the feeling of most present that we are developments in integrated optics, exotic for exoplanet research of other future ma- still enjoying a golden age of astronomical filters, etc. jor space missions including Gaia (Dimitri exploration from ground and space as Porbaix) and JWST (George Rieke). Other echoed in the subtitle of the Symposium. The mental stress was relieved by a free talks covered various proposed US space The realities now include many ground- Sunday in the middle when attendees missions including SIM (Michael Shao) based observatories operating 8–10-m- could enjoy a wide range of leisure op- and TPF (Wesley Traub), whose time- class telescopes equipped with suites of tions including swimming and playing golf scales may have unfortunately length- powerful instruments plus (great) space at the conference hotel, touring the varied ened recently as a result of NASA’s budg- observatories sensitive from gamma attractions at the bewildering array of et forecasts, and a thought-provoking to radio wavelengths and with more to nearby Disney and other theme parks or closing review by Sara Seager of the come in the near future (e.g. COROT, visiting the Kennedy Space Center with latest ideas for searching for life on extra- Herschel and Planck in Europe). Much of the Memorial Day holiday crowds. solar planets and a reminder that it may what was presented and discussed how- be vastly different from what we are used ever still falls in the category of dreams Particularly pleasing to me was the ap- to. for the future. This applies to many space parent success of the plenary conference projects; to the development of a new on “The Search for Extrasolar Planets”. Topics covered in more detail in the spe- generation of extremely large ground- This was an innovation at these meetings, cialist meetings included adaptive optics based telescopes; new interferometers; introduced to provide an opportunity for and the future and relative merits of observatories in Antarctica, etc. In most all participants to come together for half a ground, space and Antarctic interferom- of these cases, however, the funding has day to hear about developments in one etry – which have all blossomed into not yet been secured or is even already of the currently most exciting astronomi- large areas of interest within the last few in doubt. Increased efforts by the astro- cal topics engaging and motivating both years – plus the production of glass nomical community may thus be neces- the ground and space community. More blanks for large lenses and filters which sary to prolong the life of this golden age. than 1000 attendees were present for sounds less exciting but has become a It will be interesting to meet again and the introductory keynote review by Michel major issue for the development of instru- review how things have progressed in Mayor (ESO Council member) of exoplan- ments for ELTs and wide-field telescopes. two years time when this Symposium et discoveries to date which included The special courses also featured optical series will be continued in Europe, at a the discovery, announced just prior to the interferometry; adaptive optics; opto- location which has not yet been decided Symposium, of an extrasolar system mechanics in space; astronomical optics; but will most probably be in a sunny, containing three Neptune-mass planets principles of Fourier optics and diffrac- French-speaking city south of Munich. in which his group played a leading role tion; telescope systems: materials choices Hope to see you there. using the HARPS instrument at the ESO for performance and stability; use of
20 The Messenger 124 – June 2006 Reports from Observers
The Compact Discs of Post-AGB stars
Albert Zijlstra1 ellipticals, bipolars, and core-halo objects bipolar lobes to form. But detecting and Eric Lagadec1 – a few are even round. The interacting resolving such discs requires extreme Mikako Matsuura1 stellar wind model (ISW) explains these angular resolution which only now is be- Olivier Chesneau 2 structures by a spherical, fast post-AGB coming feasible from ground-based ob- Sandra Etoka1 wind blowing into the earlier, slow AGB servatories. ejecta. A snowplough develops, amplify- ing any asymmetries already present. The prototype of the bipolar post-AGB 1 Jodrell Bank Centre for Astrophysics, The model works well but requires that stars is OH231.8+4.2. It shows two Manchester, United Kingdom the original AGB wind is already strongly (ionised) bipolar lobes on either side of a 2 Observatoire de la Côte d’Azur, Nice, asymmetric. The origin of this initial asym- central obscuring lane. The obscured France metry is still not fully clear, but the most central star (QX Pup) shows Mira-like var- accepted model involves a binary system. iability, indicative of an evolved AGB Three cases can be distinguished star. We obtained a range of observa- Many post-AGB stars are predicted to tions, including AO-assisted infrared show compact discs less than ~ 100 AU 1. Common envelope systems, where the imaging (NACO), OH maser observations in size. The VLT is uniquely able to companion triggers a fast mass loss. using the MERLIN array, and VLTI/MIDI. trace these size scales, using adaptive These system will rarely reach the AGB, The resulting data are arranged in Fig- optics (NACO) and optical interferom- as the common envelope is likely to ure 1. The left panel shows the 2.12 mi- etry (VLTI). We here report on observa- develop already on the preceding Red cron image, with the base of the two tions of four such objects, showing Giant Branch. Orbital separations lobes clearly identifiable (the lobes them- direct detections of these structures. are of the order of 1 AU. Perhaps 10 % selves are much larger). The dark lane of ‘protoplanetary nebulae’ may de- is seen to consist of several substructures rive from such systems, although fewer with brighter regions embedded. The Stars like the Sun, with masses in the would evolve into PNe. right panel, (b), shows an L-band image. range 0.8–8 MA, end their active lives Here the central region shows a bright with a catastrophic mass-loss event: the 2. Wider systems, where the geometry of core, and the main dark lane is shown to so-called superwind. Within a period of the mass loss is affected, but not the be located about an arcsecond south. less than 105 yr, between 20 % and 80 % mass-loss rate itself. Orbital separa- A thin dark lane is seen towards the north. of the total mass of the star is ejected. tions are a few to tens of AU. The sys- Panel (c) shows a focus on the compact The superwind occurs on the Asymptotic tem may form a circumbinary disc. core seen on panel (b). We obtained Giant Branch (AGB). The AGB star con- They may account for ~ 25 % of the PN several VLTI/MIDI baselines across this sists of a degenerate carbon-oxygen core, birth rate. source. Fringes were detected: we es- surrounded by the nuclear burning shell, timate the core to have a diameter of ap- in turn surrounded by the convective 3. Systems with minor effects on the proximately 30–40 mas (Matsuura et al. hydrogen envelope. The superwind re- mass-loss geometry. Typical separa- 2006). moves almost the entire envelope. When tions are ~ 100 AU. The geometry the envelope mass has been reduced may show the movement of the mass- The distance to OH231.8+4.2 is derived −2 to ~ 10 MA, the photosphere collapses, losing star, as in the spiral nebula from its association with the open cluster the superwind ceases and the star around AFGL 3068 (Mauron and M13, as 1.3 kpc. The VLTI/MIDI source moves rapidly to the blue in the HR dia- Huggins 2006). The prototypical AGB has a radius of 40–50 AU, which is within gram. The star now begins to ionise star, o Ceti (Mira) has such a white range of expectations for a circumbinary the expanding ejecta, forming a planetary dwarf companion ~ 100 AU away. disc. The dark lane is very much larger, nebula. Roughly 104 yr later hydrogen at 1000 AU, and may either be a thick burning ceases and the remaining core of torus or an ionisation shadow caused by the star enters the white-dwarf cooling Circumstellar discs the inner disc. Panel (d) shows OH ma- track. The nebula fades and eventually ser data obained with MERLIN: the OH merges with the interstellar medium. The Many post-AGB stars show evidence for traces the dark lane very well. The colour superwind is responsible for such diverse dense, dusty discs. They are unresolved indicates the velocity, in m/s. Almost all aspects as the white dwarf mass distri- but show up because of the high opac- emission is blueshifted with respect to bution (and therefore the SN Ia rate), in- ity in the disc which may obscure the the systemic velocity, indicating that only terstellar hydrogen recycling (accounting star. The cold dust in the disc also adds a OH emission in front of the source is seen. half the hydrogen in the local ISM), and strong far-infrared excess with a typical This can be explained if the OH maser interstellar nitrogen, carbon and dust. spectral index (de Ruyter et al. 2006). The amplifies the radio continuum from the small sizes suggest that these discs inner ionised nebula. The velocities in- Planetary nebulae (PNe) show intricate are Keplerian and do not take part in the crease with distance from the centre, as structures, evidence that the superwind overall expansion of the (much larger) expected from an ISW-driven bipolar out- is not a constant, spherical flow. The HST nebulae. In the ISW model, the small disc flow (Zijlstra et al. 2001). planetary nebula gallery shows a stag- provides an initial asymmetry into which gering range of morphologies, including the subsequent fast wind causes the
The Messenger 124 – June 2006 21 Reports from Observers Zijlstra A. et al., The Compact Discs of Post-AGB Stars
Collimated outflow
2 Baseline 1 1 Baseline 4 (d) 0 10000 20000 30000
Central core Outflow
(a) N2.12 (b) L-band (c)
OH231.8+4.2 is the first source to show Figure 1: Composite of OH231.8+4.2. (a) 2.12 mi- all components expected from the ISW cron image. For scale, the banana-like structure (2) is 0.7 arcsec across. (b) L-band image: The posi- model: an inner disc with size consistent tion angles of the VLTI baselines are indicated. with a circumbinary disc, a bipolar out- (c) A zoom on the bright core seen in the NACO flow, and a velocity field as predicted by a L-band image. (d) OH maser velocities measured fast wind–slow wind interaction. The only with MERLIN; the colour scale is in m/s. missing ingredient is the putative binary companion. The very high opacity of the inner region may make this hard to find.
Figure 2: NACO three- A tale of two chemistries colours image of Roberts 22, combining
H2, Brγ and 2.24 μm The disc forms relatively early on the continuum images. The AGB. If, during the AGB, the continuing field of view is 7?× 7?. dredge-up forms a carbon star, the disc will show the earlier, oxygen-rich chem- istry while the current wind is carbon-rich. The oxygen-rich chemistry leads to sil- icate dust, whilst the carbon-rich wind is dominated by silicate carbide dust, and once the star becomes hotter, PAH fea- tures are seen. A number of post-AGB stars display both PAH at shorter wave- lengths, and features attributed to crys- talline silicates at longer wavelengths. This combination of incompatible chemis- tries requires distinct regions, where the PAH are located in the UV-irradiated (warm) outflow and the silicates in the opaque, cold disc. The original example of this structure is the Red Rectangle, where ISO spectra revealed the presence of the crystaline silicates. Direct imaging
22 The Messenger 124 – June 2006 Figure 3: Mosaic of images of CPD- 56˚8032. Right: HST (F435). Bottom left: MIDI 8.7 μm image (deconvolved); middle: model of the observed inner rim of the disc based on VLTI data; top: 10 μm model image of the disc observed by MIDI.
0.5
0.0 csec Ar
–0.5 1�
–1.0 –0.5 0.0 0.5 Arcsec of the silicate disc would require 20-mi- flows and directions can be interpreted in be resolved with an elliptical diameter cron observations. terms of the ’warped disc’ scenario of of 0.4 × 0.3 arcsec. The VLTI/MIDI shows Icke (2003). The OH emission shows that very weak fringes, with visibilities de- Roberts 22 is one such post-AGB star the ’wedge’ is oxygen rich. The location pending on position angle. We model which shows evidence for both oxygen of the PAH emission is at the edge of the these fringes using an ellipsoidal ring, and carbon-rich chemistry. It is a reflec- equatorial disc. with an aspect ratio of 0.5 (equivalent to tion nebula, with an obscured central a ring viewed on angle of 30˚) and a ra- star: a spectral type of A2 I was inferred dius of 75 mas. For an assumed distance from the scattered light from the two The IR-[WC] stars of 1.35 kpc, the inner radius of this inner lobes. HST images of this bipolar nebula ring is 97 AU. There is no indication for show a dark lane across the centre of [WC] stars are PNe central stars which any preferred axis in the system from our the object, with additional dark regions show emission lines very similar to those HST images and VLTI/MIDI observations. to the north, close to where the dark lane of the massive WR stars. Their origin is is least clear. The oxygen-rich nature not well understood, but the absence of The expectation that the inner disc is the is proven by the presence of OH maser hydrogen in the stellar spectra suggests location of the silicates is not fully con- emission. Figure 2 shows our VLT/ they have been fully stripped of their hy- firmed. Our VLTI/MIDI spectra show that CONICA image. Compared to the HST drogen envelope. A few of these objects a part of the strong PAH emission arises image, the dark lane is less clear (al- are extremely strong infrared emitters, from the central source. About a third though still evident from the wedge on with infrared excess (the ratio of dust lu- of the integrated flux from the 7.8 and 8.6 the left) but a bright central, resolved minosity over Lya flux) higher than in any micron PAH features are recovered from source is seen at the centre. The OH other PN. Most or all of these IR-[WC] the VLTI/MIDI spectrum, but only about maser coincides with the wedge: it lacks stars show the chemical dichotomy, with 1/4 of the 11–14-micron plateau, and the redshifted emission at the central po- both very strong PAH emission and pro- the 11.2 feature is almost absent from the sition, and this indicates a compact nounced crystalline silicates. VLTI/MIDI spectrum. Part of the difference ionised source in the centre which is opti- may arise if the PAHs in the central ob- cally thick at 18 cm. The outer emission CPD-56˚8032 and He 2-113 are two mem- ject are ionised. The observed features shows pronounced bending, and in fact bers of this group. Figures 3 and 4 show are mostly C-H modes, and therefore structures are visible at many position images of these two objects. Figure 3 the central PAHs are hydrogenated even angles. Little of this was visible in the op- shows, on the right, an HST image (F435) though the star is hydrogen poor. The tical HST image: it is possible that the of CPD-56˚8032. The nebula has an irreg- oxygen-rich material is not seen, but we scattered optical light is too much influ- ular appearance surrounding the bright note that this dust is too cold to emit enced by the limited available escape central star. The VLTI/MIDI single dish im- at 10 microns. Our model of the infrared routes from the central source, to show age shows a bright core at 8 micron: spectrum indicates that the disc extends the intrinsic structure. The multiple after deconvolution, the core is found to outwards to perhaps 1000 AU: the ob-
The Messenger 124 – June 2006 23 Reports from Observers Zijlstra A. et al., The Compact Discs of Post-AGB Stars
served core corresponds to the inner The results show the power of the new, References edge of this disc. This suggests a model high-angular-resolution observing modes de Ruyter S. et al. 2006, A&A 448, 641 where the PAHs are located at the inner available at the VLT. The origin of the Hajduk M. et al. 2005, Science 308, 231 rim of an otherwise oxygen-rich disc that structures seen in these objects are Icke V. 2003, A&A 405, L11 could be flared. The PAHs may form at found within 100 AU of the star. Adaptive Lagadec E. et al. 2006, A&A 448, 203 the turbulent, shocked interface between optics and optical interferometry are Matsuura M. et al. 2006, ApJ (Letters), in press Mauron N., Huggins P. 2006, A&A 452, 257 the carbon-rich, H‑poor wind from the uniquely able to trace these size scales. Zijlstra A. A. et al. 2001, MNRAS 322, 280 star, and the disc. Now, if only we could detect the binary He2-113 shows a more regular morphol- companions! ogy (Lagadec et al. 2006). Figure 4 shows a three-colour image with indica- tion of a large torus (~ 1500 AU) and a bipolar outflow. But there is again an infrared source located at the centre, with a diameter of ~ 150 mas, surrounded by a void. VLTI data did not show any more compact structure. The inner rim seen in CPD-56˚8032 appears to lack a counterpart in He2-113, and neither does the PAH emission show an obvious central source. The large disc does ap- pear to be present.
Binarity
All four objects show evidence for the compact disc required by the ISW model. These discs indicate likely binary com- panions, evolving through either scenario 1 or 2 above. But in none of these cases do we find direct evidence for a stellar companion. This may be understandable, in view of the large luminosity differ- ence between an AGB star and a main- sequence or white-dwarf companion, but it leaves a weak link in the argument. (One could argue that we don’t find direct evidence for the primary star either.)
The IR-[WC] stars also show the disc mor- phology, and binarity is likely for these objects. However, the strong relation be- tween emission-line central stars and the IR-bright, dual-chemistry nebulae re- mains unexplained. The late thermal pulse scenario for the [WC] stars (Hajduk et al. 2005) does not predict any link between the unusual star and the un- Figure 4: Three-colour image of usual nebula. Binary coalescence may be He2-113, combining HST Ha (coded as red), NACO L; (green) and M; considered, removing the hydrogen (blue). The bright ring is approximately envelope in the process. Otherwise, ac- 1.5 arcsec across. cretion from the circumstellar disc on the post-AGB star or a white-dwarf com- panion may be involved.
24 The Messenger 124 – June 2006 Reports from Observers
Probing the Dark Matter Content of Local Group Dwarf Spheroidal Galaxies with FLAMES
Mark I. Wilkinson1 radial length scale) which are inferred to field stars (Shetrone et al. 2001; Tolstoy Jan T. Kleyna 2 contain dynamically significant quantities et al. 2006). Thus, the Galactic halo was Gerard F. Gilmore1 of dark matter. not predominantly formed by disrupt- N. Wyn Evans1 ing galaxies like the present-day dSphs. Andreas Koch 3 The proximity of the Milky Way dSph sat- Nevertheless, the chemical properties Eva K. Grebel 3 ellites makes it feasible to obtain spectra of dSphs provide valuable insights into Rosemary F. G. Wyse 4 for large numbers of individual stars in the processes of galaxy formation and Daniel R. Harbeck 5 them, facilitating more detailed studies of evolution on the smallest scales. their properties than are possible for galaxies beyond the Local Group. These It is the large apparent mass-to-light ra- 1 Institute of Astronomy, Cambridge spectra provide radial velocities and tios of dSph galaxies, and the conclu- University, Cambridge, United Kingdom chemical abundance determinations sion that they contain significant amounts 2 Institute for Astronomy, Honolulu, USA which, respectively, enable us to to probe of dark matter, that has caused them 3 Astronomical Institute of the University the stellar velocity distribution function to attract much attention in recent years. of Basel, Department of Physics and and halo potential within a dSph and pro- The first evidence of this emerged in Astronomy, Switzerland vide detailed information about the star- 1983, when Aaronson published velocity 4 The John Hopkins University, Baltimore, formation history of these systems. measurements of three carbon stars in USA Two recent Messenger articles have dis- the Draco dSph. These data implied a 5 University of Wisconsin, Madison, USA cussed in detail the insights into the velocity dispersion for Draco of 6.5 km/s, chemical evolution of the stellar popula- from which Aaronson cautiously inferred tions in dSphs which have been gained a mass-to-slight ratio of 30 solar units. We present preliminary kinematic re- by recent observations with the FLAMES As this was significantly higher than the sults from our VLT programme of spec- spectrograph on the VLT (Koch et al. values typical of globular star clusters, troscopic observations in the Carina 2006a; Tolstoy et al. 2006). In this article this provided the first hint that the dSphs dwarf spheroidal galaxy using the we will focus on the implications of the were a class of stellar system distinct FLAMES multi-object spectrograph. kinematic data in the Carina dSph for our from the globular clusters, despite the These new data suggest that the dark understanding of the dark matter. fact that in many cases their stellar mass matter halo of this galaxy has a uniform was similar. Subsequent observations density core. The implications for our The dSphs are the lowest-luminosity sat- have borne out these early estimates and understanding of the nature of the dark ellites of the Milky Way and M31, charac- all dSphs observed to date have velocity matter are discussed. terised both by their low stellar luminosi- dispersions in excess of 6.5 km/s. ties (up to 2 × 107 solar luminosities, with the majority in the range 105–106 solar By 1998, due to the dedicated efforts of Dark matter in dSphs luminosities) and the apparent absence of several teams, velocity dispersions had gas and on-going star formation. The been measured for eight dSphs (Mateo According to the current cosmological recent discovery of the Ursa Major dSph 1998). However, dSph velocity distribu- paradigm, non-luminous, non-baryonic (Willman et al. 2005) and the Canes tions were still represented solely by the matter contributes approximately 20 % of Venatici (Zucker et al. 2006) and Bootes central velocity dispersion, which con- the overall mass-energy budget of the (Belokurov et al. 2006) dSph candidates tains only limited information about the Universe. Locally, on the scale of galaxies brings to twelve the number of dSphs nature of the system. The situation like the Milky Way, it constitutes about around the Milky Way. A similar number changed in 1997, with the publication of 90 % of the gravitating mass. Determining have been identified orbiting M31. At the first velocity dispersion profile for the nature of this dark matter is a key least one dSph is clearly being disrupted a dSph (Mateo 1997). Using 215 individual goal of contemporary astronomy. The by the tidal field of the Milky Way – the stellar velocities in Fornax, Mateo showed dwarf spheroidal galaxies (dSphs) of the Sagittarius dSph has extensive debris that the velocity dispersion remains ap- Local Group provide a particularly valua- trails which have been observed over proximately flat almost to the edge of the ble window on the properties of dark much of the sky. The stellar distributions light distribution. This profile is inconsist- matter on small (~ 1 kpc) scales. Several of most dSphs exhibit some level of dis- ent with the simplest model of Fornax of these low-luminosity galaxies have turbance in their outer regions, although in which the mass is distributed in the been found to have extremely large whether this is due to their proximity same way as the light and the stars have mass-to-light (M/L) ratios (up to 1000 in to their parent galaxies remains contro- an isotropic velocity distribution. solar units) which suggests that these versial. Although the dSphs were once are the most dark-matter-dominated stel- thought to be the primordial building The past decade has seen a rapid in- lar systems known in the Universe (e.g. blocks whose disruption contributed to crease in the size of dSph kinematic data Kleyna et al. 2001, Wilkinson et al. 2004, the hierarchical build-up of the stellar sets, driven by the availability of multi- Mateo et al. 1998). Given the apparent halo of the Milky Way, recent studies object spectrographs on 4-m to 10-m- absence of dark matter in globular star have found that the chemical composi- class telescopes which allow the simulta- clusters, they are also the smallest stellar tion of the stars in the present-day neous acquisition of spectra for large systems (in terms of stellar mass and dSphs differs substantially from that of numbers of stars. The first dSph disper-
The Messenger 124 – June 2006 25 Reports from Observers Wilkinson M. I. et al., Probing the Dark Matter Content of Local Group dSphs
sion profile based on multi-fibre observa- 25 Figure 1: Spatial distribution of Carina tions was that of Draco, based on veloc- members observed in our survey. 20 Stars approaching and receding (re- ities for 159 stars obtained using the 15 lative to Carina) are shown as blue WYFFOS spectrograph on the William and red symbols, respectively. The Herschel Telescope (Kleyna et al. 2001). 10 size of the symbol is proportional to the magnitude of the radial velocity. Since that time, dispersion profiles 5 n) The ellipse indicates the nominal tidal have been measured for all the Milky Way mi
rc 0 limit of Carina with semi-major axis dSphs. For most Milky Way dSphs, the of 28.8 arcmin. large (25 arcmin diameter) field of view of Y (a −5 the FLAMES spectrograph on the VLT −10 is ideally matched to their angular size −15 facilitating the efficient coverage of the full −20 area of each object. −25 −30 −20 −10 0 10 20 30 The properties of dSph haloes are largely X (arcmin) determined by the physical properties of the dark matter. For example, the num- ber of low-mass dark-matter haloes in global stellar kinematics of all the dSphs errors are 1.2 km/s for the entire data the vicinity of a Milky Way-type galaxy is have not yet been defined sufficiently set and 1.5 km/s for the faintest stars a strong function of the nature of the dark well to yield definitive results on the inner (V = 20–20.5). matter – cold dark matter (CDM) simu- slope of their dark matter distributions. lations typically predict hundreds of low- Our Carina data set will be sufficiently A total of 1257 targets in Carina were ob- mass haloes around the Milky Way while large to place robust constraints on the served. Of these, 535 are probable mem- warm dark-matter models contain sig- profile of a dSph dark-matter halo, while bers of Carina (based on their radial nificantly fewer. However, it is currently our modelling will further the analyses velocities). The remainder are foreground not clear which objects in the simulations of the data from all the dSphs. Milky Way stars which can be used to correspond to the observed dSphs. A investigate the properties of the velocity number of authors have claimed that the distribution of our own Galaxy (see properties of dSphs are consistent with Observations of the Carina dSph below). Of the probable members, some their residing in haloes of mass > 109 437 stars have spectra with sufficient solar masses. In this case, the numbers The Carina dSph has previously attracted signal-to-noise to enable chemical abun- of dSphs might be consistent with attention due to its unusual, bursty star- dances to be determined using the Cal- CDM simulations. One of the key goals of formation history, with the most recent cium triplet estimator (Koch et al. 2006b). our observations in Carina is to test in peak occurring around 3 Gyr ago (e.g. The spatial distribution of Carina mem- detail whether its properties are consist- Monelli et al. 2003). Its central velocity bers from our survey is shown in Figure 1. ent with those of an object with a mas- dispersion is 6.8 km/s (Mateo et al. 1993), As our primary goal in this survey is to sive, extended dark halo. implying a mass-to-light ratio of about map out the velocity structure of Carina, 30–40 (solar units). Majewski et al. (2005) it is particularly important to observe The shapes of the dark-matter density provide evidence of irregularity in the stars at large projected radii as these profiles of dSphs are also sensitive to the outer regions of the light profile, perhaps place the strongest constraints on the type of dark matter. Galaxy haloes com- associated with tidal disturbance. Our mass and extent of the galaxy. As can be posed of cold dark matter are predicted Carina data were obtained as part of seen in the figure, our targets probe to to be cusped, with the density in the in- VLT Large Programme 171.B-0520 (PI: the nominal tidal radius of Carina (around ner regions rising as 1/rn, where n lies in Gilmore). The targets were selected to lie 28.8 arcmin). Our sample increases the the range 1–1.5. Alternatively, if the dark on the red giant branch of the colour- number of measured stellar velocities for matter were warm, i.e. composed of par- magnitude diagram of Carina and span Carina members by almost an order of ticles which had a non-negligible intrin- the magnitude range V = 17.5 to 20 magnitude and extends to radii at which sic velocity dispersion, then this would (see Figure 2 of Koch et al. 2006a). The both the effects of an extended halo as lead to a shallow or uniform density core, photometric and astrometric data for well as the tidal effects of the Milky Way whose size depends on the actual ve- the input catalogue were obtained by the may be observable. locity dispersion of the particles. The pres- ESO Imaging Survey (EIS) as part of ence or absence of a cusp, as well as the Wide-Field Imager Pre-FLAMES sur- The histogram in Figure 2 shows the dis- its precise steepness is one of the most vey. The spectroscopic data were taken tribution of velocities for our full sample direct measurements of the nature of in visitor mode and reduced using the of stars along the line of sight to Carina. dark matter. There is already evidence of standard GIRAFFE reduction software, The members of Carina are clearly visible cored haloes in some dSphs (e.g. Kleyna with sky subtraction performed using our as the narrow peak centred at about et al. 2003; Goerdt et al. 2006) but the own in-house software (see Wilkinson 223.8 km/s. The systemic velocity of identification of a property of the dark et al. 2006 [in prep.] for more details on Carina is not well separated from the ve- matter requires a universal result. The the data processing). Median velocity locities of Milky Way stars along the line
26 The Messenger 124 – June 2006 350 Figure 2: Velocity distribution of all profiles for the metal-rich and metal-poor stars observed along the line of sight stars in Carina based on the above defini- to Carina. The peak due to Carina 300 members at around 223.8 km/s is tion. The amplitude of the dispersion clearly visible. profile of the metal-rich stars appears to 250 be systematically lower than that of the metal-poor stars. This is consistent with 200 their relative spatial distributions, since
N the more extended metal-poor population 150 would be expected to exhibit a larger velocity dispersion. The observation by 100 Harbeck et al. (2001) that the younger stellar populations in Carina are more 50 centrally concentrated than the older stars, combined with the age-metallicity 0 −50 0 50 100 150 200 250 300 350 relation for Carina stars identified by
vlos (km/s) Koch et al. (2006b), would then suggest an interpretation of the kinematic data in 15 ity dispersion with position in the dSph. In terms of a secondary, more recent burst Figure 3 we present the dispersion profile of star formation concentrated towards for Carina, plotted as a function of pro- the centre of Carina. s) 10 jected radius. To calculate the dispersion
(km/ in each radial bin of this profile, we as- The flatness of the velocity dispersion sume that the projected velocity distribu- profile has important implications for the
(R) 5
σ tion in each bin is a Gaussian convolved dark-matter density profile of Carina. with the stellar velocity errors (which For a stellar system in virial equilibrium, 0 are also assumed to be Gaussian). We the Jeans equations provide a simple 15 also introduce a power-law interloper estimator of the halo mass distribution velocity distribution to take account of the once the spatial distribution of the stars s) 10 presence of foreground Milky Way stars and their velocity-dispersion profile are
(km/ in our velocity samples. known. Figure 4 shows the density pro- file inferred from our Carina data set.
(R) 5
σ The dispersion profile of Carina based on We have used the surface-density pro- the complete data is remarkably flat, file determined by Majewski et al. (2005) 0 with an amplitude of about 7–8 km/s out to determine the stellar-density distribu- 0 10 20 30 to the edge of the data at a radius of tion and have assumed that the gravita- R (arcmin) approximately 45 arcmin. Koch et al. tional potential is everywhere dominated (2006b) showed that if the stellar pop- by the dark matter. Spherical symmetry Figure 3: Top: Velocity dispersion profile for all stars ulation is divided at a metallicity of is assumed and we have simplified the in Carina. Bottom: Velocity dispersion profiles for [Fe/H] = –1.68, the ‘metal-rich’ sample is form of the Jeans equations by assuming stars with [Fe/H] < –1.68 (blue) and [Fe/H] > –1.68 (red). slightly more centrally concentrated than that the velocity distribution is every- the ‘metal-poor’ population. The lower where isotropic. The black line in the den- panel of Figure 3 shows the dispersion sity plot shows the form of the density of sight. This makes it more difficult to establish membership, as simple criteria 109 (e.g. the standard velocity cut of three times the internal velocity dispersion) may include a non-negligible level of fore- ground contamination. 108 ) –3 c kp Dark matter in Carina 0 (M
ρ
The large central velocity dispersions in 107 dSphs are usually interpreted as evidence Figure 4: Mass density profile of of significant amounts of dark matter. Carina as inferred from the velocity Much stronger constraints on the amount dispersion profile using Jeans Carina of dark matter in a dSph, as well as its equations and assuming velocity 1/r isotropy. The black curve shows 106 spatial distribution, can be obtained from 10–2 10–1 100 the expected relation for a standard knowledge of the variation of the veloc- r (kpc) cusped halo.
The Messenger 124 – June 2006 27 Reports from Observers Wilkinson M. I. et al., Probing the Dark Matter Content of Local Group dSphs
profile expected from cosmological simu- gation of our Carina data, and a velocity is probed by kinematic observations. Fur- lations of galaxy formation in the cold sample towards M31, Martin et al. (2006) ther, several of the dSph mass estimates dark-matter paradigm. In contrast to the provided an alternative interpretation, presented in this plot are based only on profiles of the haloes seen in simula- namely that they detect the velocity sig- the central velocity dispersion – the mass tions, in the central regions of Carina it nature of the Monoceros ring, another scale may therefore be somewhat dif- appears that the dark-matter density is large stellar structure which is suggested ferent once detailed dynamical models close to uniform. to surround the Milky Way disc at low are completed for all dSphs. However, latitude. this plot demonstrates that it is possible We emphasise, however, that the dark- to interpret the velocity dispersions of matter density profile presented here is In order to gain a better understanding of dSphs in terms of the intrinsic properties based on strong assumptions about the what the internal kinematics of dSphs of the dark matter. stellar spatial and velocity distributions can tell us about the nature of the dark which may not be justified, particularly at matter, it is important to consider the very large radii. By assuming velocity properties of these objects as a class. In Future work isotropy, we are prey to the strongest de- Figure 5, we plot the mass-to-light ratios generacy of this problem, namely that a of the local group dSphs against their Now that velocities have been measured flat dispersion profile in an isolated dSph absolute V-band magnitudes. The figure as far out as the nominal tidal radii in can be produced either by the presence is based on that given in Mateo et al. most dSphs, the next major advance of large amounts of mass at large radii, or (1998) but includes more recent mass de- will be to obtain usefully large samples of by radially varying anisotropy in the veloc- terminations where these are available – stars at much larger radii. Although ity distribution. In our modelling of the the mass for Carina is based on the Wilkinson et al. (2004), and Munoz et al. Draco dSph (Wilkinson et al. 2002), we simple dynamical modelling presented (2005) have taken the first steps in this constructed a family of dynamical models above. The solid curve shows the ex- direction, the results are still controversial which included dark matter haloes of pected relation for a population of objects and larger data sets are needed. The varying extent, as well as radially varying with a stellar mass-to-light ratio of unity key difficulties are the large areas of sky velocity anisotropy. We are currently ex- (solar units) and a total halo mass of which must be surveyed, and the pre- tending this methodology to new dynami- 4 × 107 solar masses. In this case, the selection of targets in regions where the cal models appropriate for the (multi- total mass-to-light ratio, (M/L)Tot is simply expected surface density of dSph mem- population) case of Carina (Wilkinson et given by (M/L)Tot = (M/L)Stars + MDM/LV, bers is extremely low. However, stars in al. 2006, in prep.). These models will en- where MDM is the mass in dark matter these regions will provide extremely use- able us to quantify the properties of and LV is the total V-band luminosity. Not- ful information about dSph haloes. We the dark-matter density profile of Carina. withstanding the significant scatter about expect that at some level all dSphs must Our models incorporate multiple trac- this relation, it appears that most obser- be affected by the tidal field of the Milky er populations, to enable us to use the vations to date are consistent with dSphs Way. However, thus far there is no de- metal-rich and metal-poor sub-popula- having a common halo mass scale of finitive kinematic evidence of this process tions of Carina (and other dSphs) as around 4 × 107 solar masses, generally in any dSph. Constraining the radii at independent tracers of the underlying cored mass distributions, and a low cen- which the Milky Way begins to disturb dark-matter potential. tral dark-matter density. It is important dSphs will make it possible to derive the to note that this mass scale refers to the current total mass and extent of their In addition to their value in constraining mass interior to the edge of the stellar dark haloes. Of course, identifying funda- models of the dark matter, it has become distribution, since this is the region which mental properties of the dark matter re- apparent that our kinematic data can also be used to investigate the properties of the Milky Way velocity distribution 3.5 along the line of sight to Carina. Two re- cent papers have investigated this novel 3 possibility. Wyse et al. (2006) compared UMa Draco the velocity distributions along the line 2.5 UMi ] of sight to three dSphs (Carina, Draco V AndIX 2 Carina tot, and Ursa Minor) and found an excess of Sextans
stars with an azimuthal velocity of about M/L) 1.5 AndII
100 km/s relative to the predictions of g [( LeoII LeoI
lo Fornax smooth Galaxy models. They conclude Figure 5: Mass-to-light ratios versus 1 absolute V magnitude for Local Group that this kinematic structure, which is dSphs. The solid curve shows the seen along widely separated lines of sight, 0.5 Sculptor relation expected if all dSph haloes may be the remains of an object which contain about 4 × 107 solar masses of fell into the Milky Way at early times, and 0 dark matter interior to their stellar distributions. Arrows indicate mass may even have contributed to the for- −8 −10 −12 −14 −16 estimates which are lower limits based on central velocity dispersions only. mation of the Thick Disc. In their investi- Mv
28 The Messenger 124 – June 2006 quires that common properties in all the Acknowledgements Koch A. et al. 2006a, The Messenger 123, 38 dSphs be identified – we must therefore Koch A. et al. 2006b, AJ 131, 895 Mark I. Wilkinson acknowledges the Particle Physics Majewski S. R. et al. 2005, AJ 130, 2677 carry out similar studies of all dSphs. and Astronomy Research Council of the United Martin N. et al. 2006, MNRAS 367, L69 Kingdom for financial support. Andreas Koch and Mateo M. et al. 1993, AJ 105, 510 Finally, in the area of dynamical model- Eva K. Grebel thank the Swiss National Science Mateo M. 1997, ASP Conf. Ser. 116, 259 ling, identifying correlations between the Foundation for financial support. Mateo M. et al. 1998, AJ 116, 2315 Monelli M. et al. 2003, AJ 126, 218 kinematics and abundances of the stel- Munoz R. R. et al. 2005, ApJ 631, L137 lar populations in dSphs (e.g. Tolstoy et References Shetrone M. D. et al. 2001, ApJ 548, 592 al. 2006) is likely to provide important Tolstoy E. et al. 2006, The Messenger 123, 33 new information about the formation and Aaronson M. 1983, ApJ 266, L11 Wilkinson M. I. et al. 2002, MNRAS 330, 778 Belokurov V. et al. 2006, ApJL, submitted, Wilkinson M. I. et al. 2004, MNRAS 611, L21 evolution of these objects, which in turn astro-ph/0604355 Wilkinson M. I. et al. 2006, in proceedings of XXIst will further constrain models of any astro- Goerdt T. et al. 2006, MNNRAS 368, 1073 IAP meeting, EDP sciences, astro-ph/0602186 physical feedback on their dark matter. Harbeck D. et al. 2001, AJ 122, 3092 Willman B. et al. 2005, ApJ 626, L85 Kleyna J. T. et al. 2001, ApJ 564, L115 Wyse R. F. G. et al. 2006, ApJ 639, L13 Kleyna J. T. et al. 2003, ApJ 588, L21 Zucker D. B. et al. 2006, ApJ 643, L103
A Three-Planet Extrasolar System
Using the ultra-precise HARPS spectro- Planetary System graph on ESO’s 3.6-m telescope at around HD 69830 1 (Artist’s Impression). La Silla, a team of astronomers has discovered that a nearby star is host to three Neptune-mass planets. The in- nermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in the habitable zone. This unique system is likely further enriched by an asteroid belt.
Over more than two years, the team carefully studied HD 69830, a rather in- conspicuous nearby star slightly less orbiting their parent star with periods The outer planet has probably accreted massive than the Sun. Located 41 light of 8.67, 31.6 and 197 days. some ice during its formation, and is years away towards the constellation likely to be made of a rocky/icy core sur- of Puppis, it is, with a visual magnitude of “Only ESO’s HARPS instrument installed rounded by a quite massive envelope. 5.95, just visible with the unaided eye. at the La Silla Observatory, Chile, made Further calculations have also shown that The team’s precise radial-velocity meas- it possible to uncover these planets”, said the system is in a dynamically stable con- urements allowed them to discover Michel Mayor, from Geneva Observatory, figuration. the presence of three tiny companions and HARPS Principal Investigator. “With- out any doubt, it is presently the world’s The outer planet also appears to be lo- 1 Lovis et al. 2006, Nature 441, 305. The team is most precise planet-hunting machine.” cated near the inner edge of the habit- composed of Christophe Lovis, Michel Mayor, able zone, where liquid water can exist at Francesco Pepe, Didier Queloz, and Stéphane The detected velocity variations are be- the surface of rocky/icy bodies. Although Udry (Observatoire de l’Université de Genève, Swit- tween two and three metres per sec- this planet is probably not Earth-like due zerland), Nuno C. Santos (Observatoire de l’Uni- versité de Genève, Switzerland, Centro de Astro- ond. Such small signals could not have to its heavy mass, its discovery opens the nomia e Astrofisica da Universidade de Lisboa and been distinguished from noise by most way to exciting perspectives. Centro de Geofisica de Evora, Portugal), Yann of today’s available spectrographs. Alibert, Willy Benz, Christoph Mordasini (Physika- With three roughly equal-mass planets, lisches Institut der Universität Bern, Switzerland), François Bouchy (Observatoire de Haute-Provence The newly found planets have minimum one being in the habitable zone, and a and IAP, France), Alexandre C. M. Correia (Uni- masses between 10 and 18 times the possible asteroid belt, this planetary sys- versidade de Aveiro, Portugal), Jacques Laskar mass of the Earth. Extensive theoretical tem shares many properties with our own (IMCCE-CNRS, Paris, France), Jean-Loup Bertaux simulations favour an essentially rocky Solar System. (Service d’Aéronomie du CNRS, France), and Jean-Pierre Sivan (Laboratoire d’Astrophysique de composition for the inner planet, and a Marseille, France). rocky/gas structure for the middle one. (Based on ESO Press Release 18/06)
The Messenger 124 – June 2006 29 Reports from Observers
The Shapley Supercluster: the Largest Matter Concentration in the Local Universe
Dominique Proust1 Hernán Quintana 2 Eleazar R. Carrasco 3 Andreas Reisenegger 2 14h Eric Slezak 4 Hernán Muriel 5 Rolando Dünner 2 Laerte Sodré Jr. 6 Michael J. Drinkwater 7 Quentin A. Parker 8 Cinthia J. Ragone 5 13h
1 GEPI – Observatoire de Paris-Meudon, France 2 Pontificia Universidad Católica de Chile, Santiago, Chile 10 000 20 000 30 000 40 000 50 000 60 000 3 Gemini Observatory, La Serena, Chile 4 Observatoire de la Côte d’Azur, France Figure 1: Cone diagram (right ascen- 5 Observatorio Astronómico, Córdoba, sion) of the galaxies observed in the area of the Shapley supercluster and CONICET, Buenos-Aires, Argentina (SSC) up to a recession velocity of 6 IAG-USP, São Paulo, Brazil 60000 km/s. 7 University of Queensland, Australia 8 Macquarie University and AAO, Aus- 1987). This meant that an enormous Figure 1 shows the ‘cone diagram’ of tralia amount of matter attracted our Galaxy these galaxies. Velocity is plotted versus and the surrounding galaxies; it took the right ascension, ranging between 12h30m generic name of Great Attractor. In this and 14h30m. Each cluster of galaxies is Since the 1980s, we have known that direction, there is already the Hydra- characterised by an apparent elongated the Local Group of galaxies is moving Centaurus supercluster, whose galaxies structure along the line of sight, due to at a velocity of 366 ± 125 km/s in the have on average a recession velocity of the velocity dispersion inside the cluster. direction of Centaurus. In this region, 4 000 km/s. However, in spite of its wealth Note the presence of the foreground the well-known Shapley supercluster of of galaxies, this huge complex has only a Hydra-Centaurus supercluster. It is con- galaxies (SSC) consists of many clus- negligible gravitational effect on the Lo- nected by a bridge of galaxies to the ters and groups of galaxies in the red- cal Group. This is why we undertook a Shapley supercluster itself, whose 5 701 shift range 0.04 < z < 0.055. An interna- dynamical analysis of the SSC by study- galaxies have a mean recession veloc- tional collaboration has highlighted ing galaxies as faint as magnitude ity of 15 400 km/s. Many structures con- this greatest matter concentration in the mb = 18.0, beyond the Hydra-Centaurus nect the SSC to other superclusters, local Universe, less than 500 million complex, in an area of the sky extending underlining the filamentary distribution light years from us. The SSC may be over 30˚ × 12˚. of the matter in the Local Universe. The able to account for half of the sought longest one appears to extend out to for ‘Great Attractor’. The galaxies were selected from photo- 48 000 km/s, joining structures evidenced graphic plates of ESO, then digitised on by Einasto et al. (2001). The analysis the MAMA at Paris Observatory. The of the SSC made by Ragone et al. (2006) The supercluster of galaxies Shapley 8 observations were carried out with the based on simulations, shows that it is (SSC), located in the north of the constel- 2.5-m Du Pont telescope at Las Cam- composed of 122 galaxy systems; 60 are lation of Centaurus (a 13h25m, d –30˚), panas with the spectrograph 2D-frutti, new and 44 belong to the supercluster was observed in 1930 by Harlow Shapley; the ESO 3.60-m telescope with the (Figure 2). The galaxies contained in the he then noticed an oval cloud of galaxies OPTOPUS and MEFOS spectrographs, SSC represent an average matter over- in Centaurus which appears to be one of and the 1.8-m UKST telescope at the density of 5.4 ± 0.2, definitely larger than the richest currently detected, having Anglo-Australian Observatory with the nearby superclusters such as Horolo- dimensions of approximately 2.8˚ by 0.8˚. spectrographs FLAIR and 6dF. By sup- gium-Reticulum whose density excess is In the 1980s, this structure interested plementing the observations with ve- only 2.4. The SSC extends more than astronomers particularly because they locities from the NASA extragalactic 120 million light years, its volume being discovered that the Local Group, formed database (NED), 10 529 velocity measure- equivalent to that of a sphere of 80 mil- by about thirty galaxies surrounding us, ments were gathered, corresponding lion light years in radius: it is the largest moved with respect to the cosmic micro- to 8 632 galaxies. In the central part of matter concentration in the Local Uni- wave background frame of reference the supercluster, 92 % of the galaxies verse, less than 500 million light years at the velocity of 366 ± 125 km/s in the could be measured, and on the whole from us. direction of Centaurus (Dressler et al. 61 % of the objects were observed.
30 The Messenger 124 – June 2006 Figure 2: Distribution on Clusters of galaxies related with X-ray 0 9 000 km/s < v < 13 000 km/s sources are located at the centre of the –2 the sky of the 44 clus- ters and galaxies in the SSC, indicating the presence of gas 8 velocity range of the at very high temperature, more than ten 57 A3 SSC. Upper panel: million degrees. They were analysed clusters with velocities 25 – 6a between 9 000 and by Bardelli et al. (1996), deriving a mass 6 73 3 14 –1 7 A1 13 000 km/s. Lower M = 3.1 × 10 h Msun within a radius AS panel: clusters between –1 of 2h Mpc (h = Ho/100 km/s/Mpc). 13000 and 18000 km/s.
0) 14 -3 0 Using our catalogue, we determined the 00 336 (2 –3 4 7 8 3 δ 74 C1 luminosity and the mass of the super- 745 1 S 5 57 AS57 A3 AS 72 A3 A35 cluster using various models such as the A3 2
determination of the mass by X-ray A354
properties, the analysis of the velocity 35 fields of each galaxy cluster and the – spherical collapse model. We obtained a total luminosity of about 1.4 × 1014 h–2
times that of the Sun for a total mass of 0
–4 h m h m m m h m m 16 –1 14 20 14 00 40 20 13 00 40 the supercluster Mt = 5 × 10 h Msun. α (2000) Although very high, this mass would rep-
resent only half of that required to at- 0 13 000 km/s < v < 18 000 km/s tract the Local Group (Hoffman et al. –2 2001) in the direction of the supercluster. In addition to this, at least an identical amount of matter in the same direction 25 b – 6 must be present in order to account for 7 73 A1 57 the particular motion of our Galaxy. A3 5 16 -302 59 528 5 A355 31 42 A3 3 A3 4 2 5- 0) 1 31 2. 31 35323530 5 0 SC 00 278 A A 12 2 29 5 2 J (2 –3 6 1313 35 3556 RX References δ 5C A 3 SC A A356S A355 A 0 44 5 54 3 5 A 18 A356 3 a Dressler A. et al. 1987, ApJ 313, L37 2 A S7 74 68 1 42 A 6 59 3 5 74 AS A373 7 Einasto M. et al. 2001, AJ 122, 2222 66 A3 AS AS 3564 AS 29 35 A
35 A S7 Hoffman Y. et al. 2001, arXiv:astro-ph/0102190 A – 3 Proust D. et al. 2006, AA 447, 133 33 5 S7 35 21 A A 7 Ragone C. J. et al. 2006, AA 445, 819 AS 0
–4 14h20m 14h00m 40m 20m 13h00m 40m α (2000) Photo: H. H. Heyer, ESO
The VLT and its Auxiliary Telescopes at Sunset.
The Messenger 124 – June 2006 31 Reports from Observers
The Host Galaxies of the Brightest Quasars: Gas-Rich Galaxies, Mergers, and Young Stars
1 Frédéric Courbin sars (MV < −23.5). A new observational of ‘quasar envelopes’, and demonstrated Géraldine Letawe 2 approach is implemented, based on that they were made of gas and stars, Georges Meylan1 spatial deconvolution and decomposi- and that they were at the same redshift Pierre Magain 2 tion of the spectra. Our clean, deep, as the quasars. These pioneering obser- Pascale Jablonka1,3 spectra of quasar host galaxies show vations unambiguously established the Knud Jahnke 4 that the brightest quasars reside in connection between quasars and galax- Lutz Wisotzki 5 all types of galaxies, that their stellar ies. Yannick Letawe 2 populations are compatible with those Pierre North1 of young discs, even when the host The huge quantities of luminous energy galaxy is an elliptical one. Most of the escaping from quasars immediately leads host galaxies show prominent gas to questions about the properties of their 1 Ecole Polytechnique Fédérale de emission lines, whose metallicity sug- host galaxies. Are quasar host galaxies Lausanne (EPFL), Observatoire, gests a rather inefficient star forma- normal galaxies? Are they more massive? Sauverny, Switzerland tion. The source of ionisation of the gas Where does the matter fuelling the cen- 2 Institut d’Astrophysique et de Géo- is the quasar in 50 % of the objects. tral black hole come from? What are the physique, Université de Liège, Belgium All these objects are undergoing inter- physical processes responsible for the ig- 3 Observatoire de Genève, Sauverny, actions, suggesting that interactions nition of a quasar and what is its life-time, Switzerland play a major role in the ignition and fuel- if any typical value exists at all? The an- 4 Max-Planck-Institut für Astronomie, ling of the brightest quasars. swers to these questions rely not only on Heidelberg, Germany accurate observations of quasars them- 5 Astrophysikalisches Institut, Potsdam, selves, but also on the characterisation of Germany Quasars are among the most luminous their host galaxies. Most quasar host objects in the Universe. Powered by studies carried out over the last two de- the accretion of matter falling onto a cades concentrate on imaging and have 7 10 Because they are faint and hidden in 10 –10 MA supermassive black hole, led to the global picture that the most the glare of a much brighter unresolved they radiate at almost every wave- luminous quasars reside in large elliptical source, quasar host galaxies still chal- length of the electromagnetic spectrum, galaxies. The VLT spectroscopic obser- lenge the most powerful telescopes, from g-rays and X-rays to the radio vations described in this article support a instrumentation and processing tech- domain. Although, at the time of their dis- different picture, where galaxies of all niques. Determining their basic morpho- covery, quasars were found to be point types can harbour bright quasars and logical parameters and their integrat- sources, it was soon realised that they where gravitational interactions between ed colours is feasible, but difficult, from were in fact located in the centre of much galaxies or even mergers, play a major imaging alone. However, detailed in- larger, but also much fainter, envelopes. role in the ignition and fuelling of quasars. formation on their stellar and gas con- The envelopes of the most nearby qua- This was suggested already by the tents and on their dynamics is achiev- sars extend over a few arcseconds, mak- discovery of binary quasars (e.g., able with deep spectroscopy. We have ing it possible to obtain spectra of their Djorgovski et al. 1987, Meylan et al. 1990) completed such a deep spectroscopic external parts, even in moderate seeing but has never been investigated in detail study, with the VLT and FORS1 in MOS, conditions. Boroson et al. (1984) obtained for single quasars. for the host galaxies of 20 bright qua- the very first spectra of a small sample
HE 1503+0228 (z = 0.135) Deconvolved image with the quasar removed HST+ACS/HRC (F606W)
Figure 1: Example of an HST/ACS observation of a low-redshift quasar with its spiral host galaxy, HE 1503+0228, at z = 0.135. Even with the excellent resolution of the High-Resolution Channel of the ACS, the bright central quasar makes it difficult to see the internal parts of the galaxy. The image on the right has been spatially deconvolved and the quasar has been subtracted using the MCS de- 1 arcsec convolution algorithm. The spiral arms are now obvious even in the centre of the galaxy, as well as the bulge of the galaxy (Letawe et al. 2006b).
32 The Messenger 124 – June 2006 Figure 2: Example of spectra decomposition for the the quasar spectrum. The continuum and emis- z = 0.23 quasar HE 2345-2906, using the MCS sion lines of the host can be followed even ‘under- deconvolution algorithm (Magain et al. 1998, Courbin neath’ the quasar PSF. The height of the spec- et al. 2000). The top panel shows a portion of the trum is 19 arcseconds. The seeing during the obser- original VLT/FORS1 spectrum, after reduction and vations was 0.7 arcsecond and the spatial resolu- sky subtraction. The bottom panel shows the tion after deconvolution is 0.2 arcsecond (Letawe et spectrum of the host galaxy alone, after removal of al. 2006a). A VLT/FORS1 MOS study of quasar host galaxies
The high contrast between the central quasar and its host, and the small angu- lar size of the host are the main limita- tions to a spectroscopic study. Quasar host galaxies are typically 2–3 mag- nitudes fainter than their central quasar. Their angular size is only a few arcsec- Hβ [O III][O III] onds at low redshift (z ~ 0.1–0.3). Fig- ure 1 gives an example of a spiral galaxy hosting a quasar. Even with excellent seeing or HST data, the observations re- main challenging, because the wings of the observed PSF, even a few arcsec- onds away from the quasar, still strongly contaminate the data. Two observational strategies are then possible to minimise the mutual contamination of the quasar and host spectra: (1) to carry out ‘off-axis the host spectrum by that of the quasar. about 50 % are undergoing interactions spectroscopy’, by placing the slit of With a mean signal-to-noise of 10–20 per to the point that it is hard to even infer a the spectrograph a few arcseconds away spectral resolution element, this spec- morphological type. While the fraction from the quasar in the hope that less trum allows us to measure several of the of quasar hosts with gravitational interac- quasar light will contaminate the host important Lick indices describing the tions is about the same as for normal galaxy, (2) to develop reliable decomposi- stellar content of the galaxy. The promi- galaxies, we show with our data (see be- tion techniques in order to separate the nent emission lines are used to infer the low) that the most powerful quasars individual spectrum of the quasar from ISM gas metallicity as well as the ionisa- are systematically in hosts with signs of that of its host galaxy. We make the latter tion source (stars versus central AGN) interactions. In one extreme case, the choice for our study, which considers responsible for the measured emission host galaxy may have been even com- ‘on-axis spectra’ of 20 bright quasars line ratios. Curved emission lines are pletely disrupted in a strong collision with with the VLT and FORS1. seen in the 2-D spectra of the host galaxy a galaxy (HE 0450-2958; Magain et al. (Figure 2), making it possible to measure 2005; see also ESO Press release 23/05). We adopt the Multi-Object-Spectroscopy its velocity field. mode (MOS) of FORS1 and devise a Aside from the extreme cases, our spec- new observational strategy in which one The variety in quasar and quasar-host troscopic sample allows us to infer gen- of the 19-arcsecond-long slitlets is used properties is such that many objects in eral characteristics of quasar hosts, as to observe the quasar while the other slit- our sample require slight modifications compared with their quiescent, non-AGN, lets are used to simultaneously observe of the general techniques used to analyse counterpart. While the full analysis and field stars used as PSFs. The simultane- the sample as a whole. While a few qua- interpretation are described in Letawe et ous observation of the object of scien- sar hosts are in isolated spiral galaxies al. (2006a), we summarise here the main tific interest and of several PSF stars al- (e.g. HE 1503+0228; Courbin et al. 2002), conclusions. lows us to use the spectroscopic version of the ‘MCS deconvolution algorithm’ 10 (Magain et al. 1998, Courbin et al. 2000), HE 2345-2906 which takes advantage of the spatial information contained in the spectrum of PSF stars in order to carry out a spatial 5 ) /Å deconvolution and decomposition of the 2 cm
spectra. This strategy was already pro- s/ QSO Figure 3: Integrated spectrum of HE 2345-2906. The g/
posed by Courbin et al. (1999, 2002). It er 0 top and bottom panels display respectively the 6
–1 HOST has now been used to decompose nu- 0 spatially deconvolved quasar and host spectra, inte- (1 merous VLT spectra of quasar hosts and grated in the spatial direction. Each spectrum is ob- Flux tained by using the three FORS1 grisms G600B,R,I, of galaxies lensing distant quasars (e.g., 0.5 (R ~ 400) in order to cover the full optical range. Eigenbrod et al. 2006). Figures 2–3 give The spectra are displayed in the rest frame. Note the an example of our spectra decomposi- quasar broad emission lines, that are seen narrow tion, applied to a FORS1 spectrum of the in the host galaxy. The Ha + N ii (6565 Å) emission 0 line is even resolved in the spectrum of the host, be- z = 0.23 quasar HE 2345-2906. Both fig- 4 000 5 000 6 000 7000 cause of the lower circular velocity than in the qua- ures indicate no residual contamination of Restframe Wavelength (Å) sar (Letawe et al. 2006a).
The Messenger 124 – June 2006 33 Reports from Observers Courbin F. et al., The Host Galaxies of the Brightest Quasars
Stellar populations 0.4 Figure 4: Lick Mg2 and Hb indices for 14 of the quasar host galaxies (red symbols), compared with the non-active galaxies of Trager et al. (1998) and Studies based on imaging only conclude Kennicutt (1992). Circles stand for elliptical galaxies, that almost all of the most luminous qua- 0.3 while triangles indicate later-type galaxies. Red open sars reside in massive elliptical galax- squares indicate the objects that contain gas ion- ies (e.g., Floyd et al. 2004, based on HST ised by the central AGN itself. Our values of the Lick indices match well those measured for late-type imaging). We measure in our spectra the 0.2 galaxies. The only two objects that have metallicities 2 Mg2, H and G4300 Lick indices, indic- compatible with elliptical galaxies are undergoing
b Mg ative of the stellar content of the galaxies. interactions (Letawe et al. 2006a).
The results are plotted in Figure 4 along 0.1 with the same measurements for two control samples of non-AGN galaxies.
Most objects have stellar populations that 0 compare well with late-type rather than early-type galaxies. Only two objects –20 –15 –10 – 5 0 5 have stellar populations consistent with Hβ their early-type morphology. Quasar host galaxies show on average bluer col- ours than those of non-AGN galaxies, in- dicative of an additional underlying young stellar population (e.g., Jahnke et al. 2004) that might be explained by recent gravitational interactions. The majority Figure 5: Emission-line ratios for 14 of the quasar Ionised by nucleus of the objects we study here shows stel- host galaxies. The solid line indicates the limit be- tween objects with an ISM ionised by star formation 1 lar populations inconsistent with nor- and the objects with an ISM ionised by the central mal inactive isolated early-type galaxies quasar. Filled symbols represent objects with ob- or massive bulges, but rather shows vious signs of interactions, while open symbols are isolated objects. All objects with ionisation by the
spectral features more typical for young ] β 0.5 quasar are undergoing interactions. They also cor- /H discs. I II respond to the brightest quasars. Measurements
g [O Ionised by stars connected by a dashed line are for the same object lo but correspond to measurements in the central or Gas ionisation and metallicity external parts of the galaxy, where the ionisation 0 is found to be respectively by stars or by the AGN Disc (Letawe et al. 2006a). Emission-line ratios are well-known indi- Elliptical Undefined cators of the source of ionisation of the Undefined + YP
Interstellar Medium (ISM). We measure in –0.5 Figure 5 the [O iii]/H ratio as a function –0.8 –0.6 –0.4 –0.2 0 0.2 b log [N II/Hα] of the [N ii]/Ha ratio for 14 quasar host galaxies that have significant narrow emission lines. These two ratios compare high and low ionisation lines, hence allowing us to discriminate between high- energy ionisation sources and sources of lower energy. Galaxies where the ISM 45 Figure 6: Luminosity of the quasar in the Hb emis- sion line (erg s−1) as a function of its [O iii] (5007 Å) is ionised by star formation are there- Disc Elliptical luminosity. The typical 1-s error bar is given in fore located, in such a diagram, at a dif- Undefined the lower right corner. The characteristics of the host ferent place than the galaxies where Undefined + YP galaxies are as stated in the legend, where open the ISM is ionised by the central quasar. symbols represent isolated galaxies, and filled sym- The result is striking: half of the galax- 44 bols are for galaxies that display signs of interac- tions. It is immediately seen that the quasars with the ) ies show the signature of an ISM ionised β
H brightest emission lines tend to reside in interacting by the quasar itself. All these are under- L( systems (Letawe et al. 2006a). g going interactions. In addition, the line ra- lo tios in these objects indicate that even 43 the gas located several kpc away from the centre of the quasar is ionised by the hard radiation field of the quasar. The ob- jects are also the brightest of the sam- 42 ple, making it clear that interactions play 41 42 43 44 45 a major role in the ignition and fuelling of log L([O III])
34 The Messenger 124 – June 2006 Figure 7: Gas metallicities of the qua- the brightest quasars. Figure 6 adds 6 more support to this picture, by estab- Our sample of H II galaxies sar host galaxies (top), and of two 4 samples of metal-poor blue compact lishing a clear correlation between galaxies (middle panel), and metal- the luminosity of the central quasar in the 2 rich galaxies (bottom). Although our emission lines, and the fact that the sample is dominated by discs/spirals, quasar resides in an interacting system. 0 their metallicity remains low com- 7 7.5 8 8.5 9 9.5 pared with normal spirals, suggestive In Figure 6, all the bright quasars are of a low efficiency of star formation 15 undergoing interactions, while the faintest (Letawe et al. 2006a). Blue compact galaxies ones rather reside in disc-dominated 10 galaxies. Isolated elliptical galaxies host
only moderate-luminosity quasars. N 5
0 When the source of ionisation of the ISM 7 7.5 8 8.5 9 9.5 is stellar, it is possible to estimate the Star-Formation Rate (SFR) using the [O ii] 25 equivalent width. Although more objects 20 Spirals would be needed to draw a definite 15 conclusion, we note that three hosts out 10 of four with confirmed elliptical morphol- 5 0 ogy have significant [O ii] emission, in 7 7.5 8 8.5 9 9.5 contrast with non-AGN elliptical galaxies. 12 + log (O/H) In all the cases where it can be meas- ured, the SFR is comparable to what is ing the presence of interactions. When with a neighbour. Indeed, the companion generally found in young discs. the host is a spiral galaxy, we fit a three- galaxy seen in the HST image is at the component velocity model including a same redshift as the quasar. It is however The metallicity of the gas traces how central point mass, a rotating disc, and already apparent from the FORS1 spectra galaxies have evolved. The hosts of our a dark matter halo. The masses we com- and from the HST images that interac- sample have a mean log (O/H)+12 of pute in that way are in the range 1011− tions are or have been present during the 12 about 8.4, i.e., in the low part of the met- 3 10 MA, integrated over a 10-kpc aper- history of this elliptical galaxy. allicity distribution of spiral galaxies ture, i.e., in good agreement with the (see Figure 7). Only two galaxies have a masses of normal, non-AGN galaxies. gas metallicity well compatible with the On the role of interactions in quasar mean value of 8.8, typical for spirals. This Not all symmetrical velocity curves can formation suggests that star formation has been be adequately fitted by three-component rather inefficient, and that the ignition of models, and other structures in the qua- Accurate image-processing techniques the quasar activity might therefore be re- sar host galaxies are found to mimic ro- combined with deep slit spectroscopy lated to an early stage of evolution of their tating discs when observed at such small yields a wealth of information that makes host. Note, however, that a statistical- angular sizes. The case of HE 1434-1600 it possible to unveil connections between ly more significant sample is necessary is a good example, where highly ionised the physical properties of quasars and to confirm this trend, as we have selected gas displaying a velocity field that can be of their host galaxies. the objects where we are sure that the mistakenly interpreted as circular motion, gas is ionised by star formation, i.e., a is in fact distributed in shell-like structures We find that bright quasars do not exclu- subsample dominated by a young stellar along the slit. However, accurate fit of the sively reside in large elliptical galaxies. population. velocity curve allows us to rule out cir- Half of the galaxies in our sample show cular rotation (Letawe et al. 2004), as con- stellar populations typical of young discs. firmed by HST imaging that unveils the Dynamics details of the gas distribution in the host. A second striking result is that most of Figure 8 shows an HST/ACS image that the host galaxies, including the ellipticals, The spectral resolution of the data is suf- we have obtained for HE 1434-1600. The contain large amounts of gas. This gas ficient to derive rough velocity information host galaxy of this quasar is classified has probably been brought into the ISM on the host galaxies, as can be noticed as an elliptical galaxy using ground-based through gravitational interactions. Indeed, already from Figure 2. This information is imaging. The HST image immediately the brightest quasars are systematical- valuable, not only in estimating the total confirms shell structures. By combining ly in interacting systems, independent of mass of the galaxies when unperturbed these data with 3D spectra, as can be their morphological type, when a mor- rotation is seen, but also to unveil signs of obtained with ARGUS (Figure 9), it will be phological type can be determined at all. interactions. Indeed, all objects that show possible to decide whether the shells irregular or even distorted shapes on are expanding away from the central qua- In all galaxies with interactions, the gas is the VLT acquisition images, also have dis- sar or whether they are residual materi- ionised by the central AGN rather than turbed velocity curves, hence confirm- al left in the host’s ISM after an encounter by star formation, even several kpc away
The Messenger 124 – June 2006 35 Reports from Observers Courbin F. et al., The Host Galaxies of the Brightest Quasars
Figure 8: HST image of the z = 0.144 from the quasar. This remains true for HE 1434-1600 (z = 0.144) quasars that have large reddening values, HST+ACS/HRC (F606W) quasar HE 1434-1600. The image has been taken through the F606W filter, hence ruling out the possibility that bright using the High-Resolution Channel quasars are seen brighter because of the Advanced Camera for Surveys the dust in their host has been destroyed onboard the HST. The slit of our during mergers or encounters. Companion galaxy FORS1 spectrum is about vertical in this image. The FLAMES/ARGUS field of view is also indicated. Note the Finally, we find that quasars that reside in obvious shell-like structures that may non-interacting galaxies appear to be expand away from the quasar. The in metal-poor but gas-rich spiral galaxies. companion galaxy to HE 1434-1600 is at the same redshift and is in gravi- These galaxies harbour the less luminous tational interaction with the quasar and quasars. its host galaxy (Letawe et al. 2004).
The general picture drawn from our study FLAMES/ARGUS field of view is that the brightest quasars are clear- (7 × 11 arcsec) ly related to gravitational interactions or even mergers between several galaxies. Aside from the clear case of the brightest HE 1434-1600 (z = 0.144) [O III] (5007 Å) Continuum quasars, the fainter quasars might form in the early stage of formation of their host galaxy, which are all metal-poor, i.e., galaxies where star formation has been rather inefficient so far. While we find very large amounts of gas in the latter galax- ies, it is not clear what mechanism brings the gas to their central AGN. The mech- anisms involved are probably more ‘local’ than global mergers or interacting sys- tems, e.g., the explosion of supernovae, gravitational instabilities or bar-driven fuelling. It will be interesting in the future to investigate the correlation between quasar luminosity and the presence of bars in the host galaxy.
On the technical side, our study shows that clean, deep, multi-slit spectroscopy is a powerful way to characterise high- contrast objects such as quasar host gal- 3 arcsec (7 kpc) axies. While integral-field spectroscopy is useful in order to map the ionisation state of the gas across the galaxy and to References Figure 9: ARGUS quasi-monochromatic images of measure the velocity field of the gas, ob- the z = 0.144 quasar HE 1434-1600. The fibre size Bahcall J. N. et al. 1997, ApJ 479, 642 in this image is 0.25 arcsecond, after subsampling of taining deep continuum spectra remains Boroson T., Oke J. B. 1984, ApJ 281, 535 the original data (which have 0.5 arcsecond fibres). only accessible to slit spectra in MOS. In Courbin F. et al. 1999, The Messenger 97, 26 The seeing was 0.6 arcsecond during the obser- addition to be much more sensitive, slit Courbin F. et al. 2002, A&A 394, 863 vations. The images display the two spectral regions spectrographs and their MOS capability Courbin F. et al. 2002, The Messenger 107, 28 centred on the [O iii] (5007 Å) emission line (right) Courbin F. et al. 2000, ApJ 529, 1136 and on a continuum region (left) with the same wave- provide easy access to the PSF informa- Djorgovski S. G. et al. 1987, ApJL 321, L17 length coverage. These data allow us to trace the tion mandatory to the removal of the Eigenbrod A. et al. 2006, A&A 451, 759 gas across the galaxy and to determine its ionisation central quasar. There is therefore a strong Floyd D. et al. 2004, MNRAS 355, 196 state from the central kpc to the outer parts. How- complementarity between 3D and slit Jahnke K., Kuhlbrodt B., Wisotzki L. 2004, ever, the stellar continuum remains only accessible MNRAS 352, 399 to slit spectra, hence pointing to the complemen- spectroscopy as far as quasar host gal- Kennicutt R. 1992, ApJS 79, 255 tarity between the two techniques. axies are concerned. The general trends Letawe G. et al. 2004, A&A 424, 455 unveiled by the present 20-object sam- Letawe G. et al. 2006a, submitted to MNRAS ple call for a more systematic study in- (astro-ph/0605288) Letawe Y. et al. 2006b, in prep cluding, e.g., all known bright low-redshift Magain P. et al. 2005, Nature 437, 381 quasars and Seyfert galaxies. Magain P., Courbin F., Sohy S. 1998, ApJ 494, 452 Meylan G. et al. 1990, The Messenger 59, 47 Trager S. C. et al. 1998, ApJS 116, 1
36 The Messenger 124 – June 2006 Other Astronomical News
André B. Muller (25.9.1918–1.4.2006)
Richard M. West (Munich, Germany) Based at the University of Groningen as ber 1963 to place the future ESO observ- an associate of Adriaan Blaauw, ESO atory in Chile, André became an ESO Director General (1970–74), André worked staff member on 1 January 1964, as With great sadness, we have learned for some time at the Leiden Observatory superintendent in Chile. Together with his about the death of André Muller on station on the premises of the Union Ob- wife Louise and their six children, he 1 April, at the age of 87. Living in retire- servatory in Johannesburg, South Africa. moved from South Africa to La Serena in ment in his native Holland since 1983, Thus he was well prepared to participate March of that year and soon thereafter, he was one of ESOs true pioneers, an in the early site studies in that country. he made the first and decisive visit to the outstanding representative of the select He led the ‘Quick Look Expedition’ at the La Silla mountain, together with ESO group of European astronomers who Table Mountain in the Klavervlei Farm Director General Otto Heckmann. He was succeeded in steering ESO through the area in 1959–60, reporting to the ESO closely involved in the acquirement of difficult initial phases. André was close- Committee (the precursor of the Council) this exceptional location and was respon- ly associated with the entire process, in July 1960. He went on to supervise sible for the smooth establishment of from the first site monitoring programmes several stages of the following ‘Compre- the extensive infrastructure needed to run in South Africa to the subsequent search hensive Programme’ that included testing an observatory in the middle of the desert. in Chile, the decision in favour of the at four different observing sites in 1961– He set up the Pelícano base camp and La Silla site, as well as the management 63. Site monitoring in those days was traced the path along which the road to of ESOs early activities in Chile, includ- very hard work indeed, as illustrated by the summit was later constructed. He had ing the construction of the headquarters the following instructions: “… Observers an incredible workload over the next and observatory and the installation of and assistants have to work during 25 years, as the buildings were constructed the first generation of ESO telescopes. consecutive nights and after this period and the telescopes began to arrive. In Few persons, if any, have been so inti- have to take leave during five consecutive March 1966, Council held its first meeting mately connected to the setting-up of nights. ... With the exception of these five in Chile and the La Silla road was dedi- ESOs facilities and it would be impossible nights, there will be no opportunity for cated. On this occasion, great admiration to list in detail all of the services André outings, whatsoever …” It was during this was expressed for André Muller and performed for the organisation with such period that André concluded that the as- his able team of Chileans and Europeans. great expertise and zeal during his long tronomical quality of a site is critically Work also proceeded on the ESO Head- career. dependant on the amount of temperature quarters in Chile at the Vitacura site in the change during the night: the less, the capital, Santiago de Chile. At the end André Muller obtained his PhD in Leiden better. of this exceedingly busy period, the offi- in 1953, with a study of the variable star cial dedication of the La Silla Observatory XZ Cygni. His thesis advisor was Pieter As ESO began to orient itself towards took place on 25 March 1969, with the Oosterhoff, one of the twelve leading Eu- Chile, André Muller was sent to that associated visits and a major international ropean astronomers who authored the country in late 1962 and joined Jürgen symposium in Vitacura on the Magellan- historical statement in January 1954 that Stock’s travelling team. Following the ic Clouds, the proceedings of which were ultimately led to the creation of ESO. decision by the ESO Council in Novem- edited by André Muller. Photo: EHPA, made available by J. Rösch
Searching for a site in March 1964: Jean Rösch (left) and André B. Muller (right) in front of the mountain Cinchado.
The Messenger 124 – June 2006 37 Other Astronomical News
Having done far more than any call of task, the Southern Sky Surveys. Work- All of us who had the privilege to work duty, André Muller then transferred in ing in close contact with the ESO Tele- with André Muller will remember him not October 1969 to the Office of the Director scope Project Division at CERN, he con- only as an extremely competent astrono- General in Bergedorf near Hamburg, tributed to the development of the first mer/instrumentalist/manager in his many Germany. Here he assumed the crucial computer-based telescope control sys- functions, but also as a delightful and task of leading the ESO Visiting Astron- tem. Together with Hans-Emil Schuster, friendly person. He was always ready to omers Programme, being responsible for who had worked with André in Chile help and to provide guidance from his the scheduling of the rapidly growing since 1964 and who was responsible for rich experience. Few possessed his inti- number of observing programmes with the operation of the Schmidt telescope, mate knowledge of the organisation and the expanding telescope park at La Silla. he spent much time at La Silla over the its colourful history. He continued to supervise the important, next years in order to tune this very deli- preparatory seeing studies for the 3.6-m cate instrument to optimal performance. Thank you André, for your kindness and telescope dome. From now on, André By the end of September 1983, André your great services to ESO and all would also remain closely connected to Muller left ESO for a well-deserved retire- those young European astronomers who the 1-m Schmidt telescope project. This ment in his native country. Unfortunately, gained access to some of the best ob- instrument was under construction in André and Louise would only be together servational facilities in the world. We will Hamburg but had become somewhat a few years, before she died in March never forget what you have done for as- delayed and now needed a firm hand to 1987. tronomy! get ready as soon as possible for its main
Finnish Parliamentary Committee at ESO Headquarters
Claus Madsen (ESO) Dr. Ilkka Taipale, MP, asking a question to the ESO team. At the centre, Committee Chairperson On 15 March, members of the Education Ms. Kaarina Dromberg, and Culture Committee of the Finnish MP and Mr. Tuomo Hänninen, MP (right in Parliament paid a visit to the ESO Head- Photos: H. H. Heyer, ESO the picture). quarters. The guests were welcomed by the Director General in her office. Fol- lowing this were extensive briefings on the main activities of ESO by various ESO staff members. After the session, the deputies had a chance to visit the Sci- ence Archive and the Optics Laboratory, followed by a late lunch. Finland is the most recent member of ESO and there was a strong interest by the delegation members to learn more about the work and the projects carried out by our or- Several Committee ganisation. Amongst the many topics dis- members showed considerable interest cussed were also the role of astronomy in Adaptive Optics. in science education and the SAMPO project, which is part of the initial Finnish contribution to ESO.
38 The Messenger 124 – June 2006 Other Astronomical News
Report on the ESO-FONDAP Conference on Globular Clusters – Guides to Galaxies held in Concepción, Chile, 6–10 March 2006
Tom Richtler1 workshops on star clusters have been galaxies, both in the halo of M31 and in Søren S. Larsen 2 organised since the Pucón meeting, and the discs of lenticular galaxies. Young, star clusters are often included in many massive star clusters (YMCs) in actively other contexts (e.g. star formation, galaxy star-forming galaxies were discussed 1 Universidad de Concepción, Chile evolution), but it seemed very timely to in several talks and the identification of 2 University of Utrecht, the Netherlands meet once again in 2006 and discuss the these objects as young versions of globu- vast amount of progress made. lar clusters is becoming less controver- sial. Populations of intermediate-age (few Background and venue The venue of the conference was the gigayears) star clusters have now been Lecture Hall of the Universidad de Con- identified in some merger remnants and The role of ESO in the development of cepción in the Facultad de Humanida- may provide a crucial ‘missing link’ be- astronomy in Chile is difficult to overstate. des y Arte on the university campus. Many tween the rich populations of YMCs ob- However, the Chilean government is also of the participants stayed at the Hotel served in starbursts and mergers and the well aware of the significance of science Araucano in central Concepción, where ‘classical’ old GCs. However, explaining for the development of the country and also the welcome reception and con- the differences in the mass functions of has created large programmes for Chile- ference dinner were held. With about young and old star clusters continues to an science to grow and maintain a sci- 150 participants and many more requests be a field of active investigation. Increas- entific productivity competitive with that for contributed talks than available slots, ing amounts of data are being collected of countries with a longer scientific tradi- putting together the schedule was not an for very young, still embedded star clus- tion. One of these programmes is called easy task. The final programme was busy ters, which may provide important clues FONDAP (Fondo de Investigación Avan- with 23 review talks and 43 contributed to the star-formation process leading zado en Areas Prioritarias) and there is no talks, distributed over the five days (with to GC/YMC formation. Such studies are question that astronomy is a priority field Wednesday afternoon free). In addition, likely to receive a tremendous boost once in Chile. The astronomy FONDAP pro- 58 posters were presented at the meet- ALMA comes on-line. gramme (www.cenastro.cl) unites groups ing. While the tight schedule unfortunate- from Santiago (Universidad de Chile, Uni- ly did not allow for a dedicated poster Observational studies of extragalactic versidad Católica) and Concepción (Uni- session, the posters were permanently globular clusters are becoming more versidad de Concepción). One of the mounted in the lobby adjacent to the lec- quantitative and detailed. Five years ago, FONDAP goals is to support schools and ture hall so that poster viewing was pos- little information was available about conferences. Since globular clusters sible during every coffee break. the age distributions of globular clusters play an important role in the research of beyond the Local Group. In the mean- the Concepción group, we had the feel- In the following, we describe in a general time, several spectroscopic and photo- ing that a small workshop of two or three manner a few of the topics discussed, metric studies have been published and days on globular cluster research would omitting all author names. The forthcom- tighter constraints are becoming avail- be due. But the reaction from the com- ing proceedings will give the full credit able, although the measurements are munity was overwhelming and within a to individual researchers. demanding and the presence of interme- short time we had to drop the idea of an diate-age GC populations in early-type intimate workshop and instead had to galaxies is still debated. Even so, the face the challenge of a full-scale interna- Scientific topics distinction between ‘old’ and ‘young’ is tional conference, which would stretch still one between formation redshifts our organisational and infrastructural ca- The selection of scientific topics dis- greater or less than 1.5–2, and it would pabilities to the limit. As so often, ESO cussed at the meeting already reflects clearly be desirable to push the limits was very generous and so a joint ESO- much of the progress made over the further than that. Doing so for large sam- FONDAP conference on Globular Clus- past five years. The trend from previous ples of clusters may have to await fu- ters in Concepción became reality. meetings to view globular clusters ture generations of extremely large tele- (GCs) as members of an increasingly di- scopes. Constraints on alpha-to-Fe The conference marked the five-year an- verse ‘zoo’ of star clusters continued. abundance ratios are becoming available niversary of the first-ever IAU symposium At the high-mass end of the mass spec- from spectroscopy. An entirely new on Extragalactic Star Clusters (also trum, several contributions discussed the avenue of research is abundance analysis the first IAU Symposium on Chilean soil) objects now commonly referred to as of extragalactic star clusters from high- which was held 2001 in Pucón and was ‘Ultra Compact Dwarfs’ (UCDs). It does dispersion spectroscopy, with some first also co-organised by the Concepción not yet seem quite clear whether UCDs results being presented at this meeting. group (Doug Geisler). In the intervening are a distinct class of objects, or if there In principle, this would already have been five years, an ESO workshop on the sub- is a gradual transition from high-mass observationally possible five years ago ject was organised in 2002 in Garching GCs to UCDs and dwarf galaxy nuclei. with HIRES or UVES, but only now has (Markus Kissler-Patig) and another meet- Populations of relatively faint, extended the modelling of integrated GC spectra at ing (primarily devoted to young star star clusters which do not fit the clas- high resolution reached a sufficiently clusters) was held in Cancún, Mexico, in sical description of globular clusters are mature level to allow a meaningful anal- November 2003. Several other smaller now also being discovered in several ysis. Other new results on old GCs
The Messenger 124 – June 2006 39 Other Astronomical News Richtler T., Larsen S. S., Conference on Globular Clusters – Guides to Galaxies
included the discovery of a colour-lumi- Our own Galaxy and other galaxies in the the observed, virtually universal mass nosity relation among the metal-poor Local Group will always be those that can function of old globular clusters as a re- globular clusters (the ‘blue tilt’), and the be studied at the greatest level of detail sult of evolution from an initial power- possible presence of intergalactic glob- and serve as comparison cases for more law distribution, except under special ular clusters in some rich galaxy clus- distant systems. Although the emphasis circumstances. The fractal structure of ters. There was also a lively discussion of was on extragalactic GCs, a few talks the interstellar medium might play an im- the colour bimodality in globular-cluster covered classical topics in Galactic GCs portant role. systems and its interpretation as a met- (abundances, stellar-mass functions, allicity bimodality, a subject that has re- CMDs) with less classical results. In par- cently become quite controversial. ticular, complementary information about Final remarks the stellar populations in many Local As in many other fields, large data sets Group galaxies is available by other means The lively response of the community are playing an increasingly important role (e.g. from studies of field stars). Cata- attested to the fact that research in glob- for research in extragalactic globular logues of globular clusters in M31 are still ular clusters is as active a field as clusters. One example is the ACS Virgo being improved and a large amount of ever. As noted by William Harris, a good and Fornax surveys, which provide high- photometric and kinematic information is indicator of the health of any field is its quality imaging of more than 100 early- now available for GCs there, which can ability to attract new bright students, and type galaxies and their globular-clus- be compared with other constraints on there were many examples of this in ter systems and were covered in several the accretion/merger history of M31 from Concepción. When will there be nothing talks. This has allowed many results to be studies of tidal streams. One controver- left to work out for the next generation? established with much greater signifi- sial issue is the presence of intermediate- Perhaps this will be when the actual cance than before. For example, correla- age globular clusters in M31, where cluster-formation processes and their de- tions between the mean colours (metal- adaptive optics imaging suggests that at pendences on physical parameters licities) of globular cluster sub-populations least some objects previously identified and environment are understood, when and luminosities of their host galaxies are as such may instead be loose groupings nucleation of galaxies is understood, better revealed in these new data, and of stars (‘asterisms’) and not real GCs. when star formation is understood, when more accurate measurements of globular Detailed studies of star clusters in M33 chemical enrichment is understood, in cluster sizes are possible with the better are more scarce, although it is now other words: not too soon. Globular clus- spatial resolution of ACS compared to catching up with its larger cousins. In par- ters are involved in so many aspects of earlier WFPC2 studies. Interesting links ticular, M33 is interesting because of its galaxy formation and evolution that they are also appearing between galaxy nuclei relatively rich population of young popu- are really “Guides to Galaxies”. and supermassive black holes, whose lous star clusters. masses follow very similar scaling rela- Our field seems well prepared to take ad- ions with respect to the host-galaxy mass. While research in extragalactic star clus- vantage of the many new facilities that ters remains dominated by a flurry of will become available in the next decade Dynamics of globular-cluster systems is observational results, an increased inter- and beyond (ALMA, ELTs, JWST). We another case where large data sets are play with theory is now forthcoming. are therefore confident that there will be playing an important role. Several hun- Several talks covered aspects of galaxy ample supply of new results for the next dreds to ideally 1000 or more radial ve- formation and evolution in the cosmo- many more meetings to come. locities are needed in order to carry out a logical context, and it is encouraging to satisfactory modelling of the kinematic see that cosmological simulations are properties of GC systems. With such da- starting to reach a resolution and sophis- Acknowledgements ta sets, it becomes possible to put con- tication including dissipational processes, Many thanks to all who helped making the con- straints on the detailed dark-matter distri- where the formation of globular cluster- ference possible: FONDAP Centre of Astrophysics, butions in galaxies, test alternative sized objects can be addressed. Different ESO, Las Campanas Observatory, Cerro Tololo theories to dark matter (e.g. MOND), and views about galaxy formation and the Observatory, Universidad de Concepción. The tire- determine the radial anisotropy of the ve- role of accretions, mergers and early col- less work of the Local Organising Committee was absolutely essential. Maria Eugenia Geisler, with her locity distributions, which has impor- lapse are now starting to converge, al- engagement and her skills, deserves most of the tant implications for the dynamical evolu- though the details are not yet clear. The credit. Finally, we want to thank all participants for tion of GC systems. Such data sets are spatial distributions of GC systems may their enthusiasm which made the conference such a now becoming available, thanks to effec- even provide constraints on truly cosmo- scientifically (and non-scientifically) enjoyable event. tive multi-object spectrographs on larger logical questions such as the epoch of telescopes (GEMINI/GMOS, VLT/FORS2, reionisation. N-body simulations are now FLAMES, VIMOS, Magellan/IMACS, able to model star clusters with GC- Keck/DEIMOS, etc.). like masses over cosmological time- scales, resulting in a better theoretical understanding of the dynamical evolution of star clusters. However, the simula- tions are still having difficulties producing
40 The Messenger 124 – June 2006 Other Astronomical News
Fellows at ESO
Andreas Lundgren Andreas Lundgren
I arrived in Chile as an ESO fellow in September 2004 and I was immediately thrown into the buzzing APEX project, which back then still had one year left to inauguration.
Even if I have worked with data in most wavelength regimes, my scientific work is mostly based on millimetre and sub- millimetre data. More specifically, I am interested in the distribution, kinemat- ics and physical properties of the molec- ular gas in spiral galaxies. In my thesis I concentrated on the nearby barred spiral galaxy M83, and this galaxy is still the core of my science. ly clear: Sitting in a container at 5 100 m After the defence of my thesis, I decided I was born in Sweden, and I did my un- altitude, and while observing, sniffing to see the other side of submillimetre dergraduate studies in Gothenburg, oxygen. Outside there is nothing but rock astronomy, going from the development and graduate studies at the Observatory and sand, and one of the driest atmos- of detectors in the lab, to their use in an of Stockholm. During my PhD years pheres on earth. astronomical observatory. I arrived in I did several observing trips to the SEST, Chile in May 2004 to work at the APEX and I really enjoyed visiting La Silla. telescope near San Pedro de Atacama. Therefore it was an easy decision to Vincent Reveret APEX is one of these new-generation make when I was offered the opportunity telescopes, like ALMA or the HERSCHEL to take a sabbatical year from my PhD Since I started to study physics, I have satellite, that lead the ‘revolution’ in studies 2002–2003 in order to work at always been interested in optics and submillimetre astronomy. Even if working SEST. all the incredibly different ways to detect conditions at APEX can be difficult light. After graduating in applied physics (oxygen molecules are very rare up on SEST and APEX are in many aspects in England, I did my PhD in Saclay near the telescope site!), I love going there similar, but some things are very different. Paris. I specialised in the development of because of San Pedro’s beauty and the When we operate APEX from the base a new kind of detector for submillimetre excellent working atmosphere in the station in Sequitor, some 70 km from the astronomy, the so-called large bolometer team. site, the work is very much like sitting arrays (the equivalent of CCD camer- in the SEST control room with the dark as for submillimetric range). That was a With the next arrival of a large bolometer curtains down. But when we go to Chaj- pleasant time: a very good team spirit camera (called LABOCA), APEX will nantor in order to carry out morning or associated with the successful develop- be one of the most powerful submillime- daytime observations (Since APEX is a ment of a totally new kind of detectors. tre telescope in the world. We know radio telescope, it can be used 24 hours I thought I could never find such a nice that many astrophysical hot topics can per day) the differences becomes vivid- lab again. I was wrong. benefit from APEX capabilities, like star formation for example. This is one part of my research: I study the rela- tionship between intense UV fields com- ing from OB associations and the conditions of star formation inside long columns of gas (sometimes called elephant trunks). I still work in instrumen- tation, even if now I focus more on simu- lations to prepare for the next genera- tion of bolometer cameras that maybe we will see on APEX one day ...
Vincent Reveret
The Messenger 124 – June 2006 41 Other Astronomical News
Walloon Space Days
Claus Madsen (ESO) Jean-Pierre Swings (University of Liège), Roberto Gilmozzi and Philippe Dierickx (ESO) On 28–29 March, the Cluster Wallonie taking questions from Espace, mainly a partnership of compa- the floor. nies in the Walloon ‘Space Valley’, or- Photos: H. H. Heyer, ESO ganised the first so-called ‘W Space Days’ at the Colonster Castle, located on the premises of the University of Liège. The primary aim of these days is to encour- age meetings between professionals in the sector and to identify new scientific and technological opportunities. They should also help to raise awareness of the activities of the space sector amongst the general public and young people in particular. Indeed the event successfully brought together scientists, industrialists, funding agencies and policymakers. On the first day, some 210 representatives of research centres, industries and organi- sations from 13 countries in Europe par- Marie-Dominique ticipated in the professional event, while Simonet, Minister for Science, New Tech- the next day was a ‘public day’. The first nologies and External morning’s programme comprised a series Relations for the Wal- of talks, including ELT presentations by loon regional govern- Roberto Gilmozzi and Philippe Dierickx. ment was the guest of honour at the demon- stration of the fourth The event coincided with the completion VLT Auxiliary Telescope of the fourth VLTI Auxiliary Telescope and in the AMOS assembly the programme thus included a celebra- hall. tion and a press conference at the AMOS factory, located in the nearby Liège Science Park. The afternoon offered op- portunities for company consultations and the day finished with a well-attended public lecture by Philippe Dierickx. On the following day, university students had a chance to see the Auxiliary Telescope at AMOS. As an extension to the pro- gramme, AMOS opened its doors again to the public on 1 April, with more than 450 visitors learning about the VLTI ATs. From the AT4 Ceremony at AMOS. W Space Days will be organised again in 2008, providing an interesting forum for discussion of current and future pro- grammes in astronomy, astrophysics, and astronautics, for the members of the Cluster Wallonie Espace, but – with broad European participation – also ex- tending far beyond this region.
42 The Messenger 124 – June 2006 Other Astronomical News
Schoolchildren Worldwide Compete to “Catch a Star!”
Douglas Pierce-Price (ESO) More than 130 teams from 24 countries larly well in the competition. For example, worldwide took part. They chose an 10 out of the 11 students who won travel astronomical object, such as a nebula, prizes are girls. There was also, as we “Catch a Star!”, an international competi- star, planet, or moon, or a more gen- have consistently seen in ESO’s educa- tion for school students organised by eral theme such as ‘black holes’ or ‘star tional projects, a strong showing from ESO’s Educational Office and the Euro- formation’. They then wrote about this central and eastern European nations. It pean Association for Astronomy Edu- topic, researching and discussing how would be interesting to analyse these re- cation, has had its fourth successful year. large telescopes such as those of ESO sults further, to investigate whether there could be used to study it. Younger stu- are specific reasons for the girls’ suc- The competition encourages students dents were invited to take part in a cess, and why certain countries are par- to work together in teams, learning about separate picture competition, for which ticularly well represented. Such an anal- astronomy and discovering things for they created a large number of very im- ysis could provide useful information for themselves by researching information. pressive drawings and paintings. future educational projects. The most important goal is to develop an interest in science and astronomy Other prizes, of astronomy posters and About the same number of countries took through investigation and teamwork. This CD-ROMs, were also given. Some were part as last year, with more than half is why many of the prizes are awarded awarded by lottery, and some as ‘highly of the entries coming from just three by lottery, to make the competition inclu- commended’ prizes by the jury. For the countries. Our aims for the future are to sive and avoid a sense of elitism. There picture competition, all the children won make the competition easier to enter, are, however, also four major travel prizes “Catch a Star!” T-shirts, with other prizes and to widen participation. We hope that which are awarded by jury. “Catch a awarded with the help of a public web- even more students, from even more Star!” was originally open to European based vote. countries, will “Catch a Star!” next time. countries and Chile, but from this year the competition was made truly interna- Given the importance of gender issues in Find out more about the competition at tional. science, and especially physics, it is en- http://www.eso.org/catchastar/ couraging to note that girls did particu-
Prize Project Students Teacher/Group leader Country Table of winners of Trip to ESO at Paranal Star clusters and Edina Budai Akos Kereszturi Hungary the “Catch a Star!” travel and Santiago (Chile) the structure Andrea Szabo prizes. of the Milky Way Judit Szulagyi Trip to Königsleiten The Fireworks Galaxy – Alexandra Georgieva Petar Todorov Bulgaria Observatory (Austria) NGC 6946 Rumen Stamatov and ESO Headquarters Trip to Wendelstein The Annular Solar Aida Pallàs Ramos Anicet Cosialls Manonelles Spain Observatory (Germany) Eclipse versus Violeta Porta Alonso and ESO Headquarters the Venus Transit Alícia Tiffon Calvet Trip to Hispano- Sunspots Denitsa Georgieva Dimitar Kokotanekov Bulgaria German Astronomical Tanya Nikolova Observatory at Rositsa Zhekova Calar Alto (Spain)1
1 This prize was kindly provided by Spain’s Consejo Superior de Investigaciones Científicas.
Two of the winners of the drawing competition section of “Catch a Star!”, by Karolis from Lithuania (left) and Yuriy from Belarus (right).
The Messenger 124 – June 2006 43 Other Astronomical News
A Solar Eclipse Expedition to Turkey
Stefan Uttenthaler (ESO) Figure 1: Image of the on behalf of all the participants listed in corona obtained by combining digital photos the caption to Figure 3 taken by Karl Thurner and by Thomas and Claudia Winterer. On 29 March 2006, a total solar eclipse occurred over South America, Africa, Turkey, Russia and Kazakhstan. It was the first one close to central Europe after the eclipse of 11 August 1999, and was calculated to have a maximum duration of totality of 4min 7sec. A group of eleven persons from ESO, accompanied by three from MPE and several amateur as- tronomers from the Augsburg area (altogether 20 participants) travelled to the Antalya region of Turkey to observe the eclipse. The Turkish Riviera could be rated as a good, but not excellent ob- serving site, with a probability of seeing the eclipse of 48 % for Antalya.
The weather on the eclipse day was very good with wind coming from the South, dissolving the clouds along the coast and building them up in the mountains inland. Our observing site was a remote hill lo- cated between Side and Antalya close to the coast. The exact GPS coordinates were determined by Christian Clemens to be 36˚ 52; 18?.8 N 31˚ 13; 52?.8 E. The du- ration of totality at this place was calcu- Figure 2: The diamond lated using an on-line JavaScript1 to be ring effect, captured by Christian Clemens. 3min 42sec. The eclipse took place in the early afternoon.
Our photographic and observing equip- ment was very diverse and aimed at capturing the prominences, the corona, the mysterious shadow bands as well as the surroundings. The event itself was very hectic for the photographers among us, and a simply breathtaking view for those who were just enjoying the specta- cle. We celebrated the event with cham- pagne. The fully successful photo cam- paigns certainly were another reason to celebrate (Figures 1 and 2). Figure 3 shows a group picture of the expedition crew. The happy faces show what an Figure 3: The ESO expedition crew. Back row (from exciting event it was for all of us, and left to right): Alexander Stefanescu, Christian Clemens, Arjan Bik, Stefan Uttenthaler, Christiane plans are already being made for trips to Leitner, Jürgen Keberle, Bruno Rino, Karl Thurner, upcoming solar eclipses! Françoise Delplancke, Stefan Ströbele, Yuri Bialetski, Thomas Winterer. Front row: Thomas Eimüller, 1 Eclipse calculator: http://www.chris.obyrne.com/ Jochen Sokar, Burkhard Wolff, Margrethe Wold, Eclipses/new-calculator.html Barbara Sokar, Nataliya Prymak, Anna Beletskaya, Claudia Winterer. Sebastian Deiries observed the eclipse from a different site in Kemer, south-west of Antalya.
44 The Messenger 124 – June 2006 Announcements
2007 ESO Instrument Calibration Workshop
23–26 January 2007, ESO Headquarters, Garching, Germany
The ESO La Silla Paranal Observatory Therefore, we invite you to join us at The workshop will be focused on ESO (LPO) is currently operating 19 optical, the first ESO Instrument Calibration instrumentation. A limited period of the NIR, and MIR instruments (9 VLT, 2 VLTI, Workshop to be held from 23–26 Janu- workshop will be dedicated to new instru- 8 La Silla). To monitor and calibrate both ary 2007 at the ESO headquarters in ments on the horizon of the LPO, i.e. the performance of each of these instru- Garching, Germany. the VST, VISTA, and the VLT second gen- ments and the quality of the data they eration instruments. Future challenges deliver, ESO executes dedicated calibra- The goals of this workshop are to foster as arising with ELT instrumentation are of tion plans. These systematic and regular the sharing of information, experience interest for the workshop but their pres- measurements further aid in the calibra- and techniques between observers, in- entation will be limited to invited talks. We tion of data from science programmes, at strument developers, and instrument expect that this workshop will lead to least to specified levels of accuracy. operation teams, to review the actual pre- improved calibration plans to the benefit cisions and limitations of the applied in- of the entire ESO user community as well The first ESO/ST-ECF workshop on cali- strument calibration plans, and to collect as the ESO Science Archive. brating and understanding HST and the actual and future requirements by the ESO instruments was held in 1995 to ESO users. ESO Organising Committee: Reinhard review the calibration strategies of HST Hanuschik, Andreas Kaufer (chair), and ESO La Silla instruments and to Workshop topics are the calibration and Florian Kerber (co-chair), Nando Patat, prepare for the start of operation of the data reduction of Michele Peron, Martino Romaniello, VLT. – Optical Spectro-Imagers Michael Sterzik, Christina Stoffer, Lowell – Optical Multi-object Spectrographs Tacconi-Garman. Now in 2006, after seven years of sci- – NIR and MIR Spectro-Imagers ence operation with the innovative, com- – High-Resolution Spectrographs Workshop webpage: plex, and still growing instrumentation – Integral Field Spectrographs http://www.eso.org/cal07 suite at the VLT, it is timely to review the – Adaptive Optics Instruments Contact: [email protected] achievements and limitations of the es- – Polarimetric Instruments tablished instrument calibration plans – Wide-field Imagers together with the ESO user community. – Interferometric Instruments – Pipelines, Quality Control, Science Archive, AVO, Data-Reduction Systems, Software and Techniques.
Towards the European Extremely Large Telescope
27 November–1 December 2006, Marseille, France
European astronomical research is at a and means of that ambitious long-term sessions. Invited speakers will introduce critical juncture with the European Ex- programme. It will successively address the sub‑sessions of the Science and tremely Large Telescope (E-ELT) project the E-ELT Science case, its basic ref- Instrumentation sessions. Some impor- currently being defined by the ESO ELT erence design and instrumentation con- tant deadlines are as follows: Project Office with a large involvement of cepts. – Paper and poster submission: the community through, in particular, 31 July 2006 topical working groups, OPTICON and The meeting is organised in three main – Author notification: 30 September 2006 the ELT Design Study, and with a de- sessions: Science (1.5 days), Presenta- – Final programme: 31 October 2006 cision to proceed designing the facility to tion by ESO of the E-ELT status and dis- be taken end 2006/early 2007. This meet- cussion (1.5 days), Instrumentation For further information, see http://www. ing will offer the European astronomi- (1 day). Contributed talks (approximately popsud.org/elt2006/index.php cal community at large the opportunity to 15 minutes each) and posters are invited provide precious feedback to the goals for the Science and Instrumentation
The Messenger 124 – June 2006 45 Announcements
ESO Fellowship Programme 2006/2007
ESO awards several postdoctoral fellow- in Santiago, at the ESO Headquarters ships begin between April and October ships each year. The goal of these fel- in Garching, or at any institute of astron- of the year in which they are awarded. lowships is to offer young scientists op- omy/astrophysics in an ESO member Selected fellows can join ESO only after portunities and facilities to enhance state. having completed their doctorate. their research programmes at one of the world’s foremost observatories. All fellows have ample opportunities for The closing date for applications is scientific collaboration within ESO, both 15 October 2006. With ALMA becoming operational in a in Garching and Santiago. For more few years, ESO offers ALMA Fellowships information about ESO’s astronomical Please apply by filling the form available to complement its regular fellowship pro- research activities please consult http:// at http://www.eso.org/genfac/adm/pers/ gramme. Applications by young astrono- www.eso.org. A list of current ESO staff forms/fellow06form.pdf attaching to your mers with expertise in mm/sub-mm as- and fellows and their research interests application: tronomy are encouraged. can be found at http://www.eso.org/ – your Curriculum Vitae including a science. Additionally, the ESO Headquar- (refereed) publication list In Garching, the fellowships start with an ters in Munich, Germany, hosts the Space – your proposed research plan (max. two initial contract of one year followed by Telescope European Coordinating Facility pages) a two-year extension (three years total). and is situated in the immediate neigh- – a brief outline of your technical/obser- The fellows spend up to 25 % of their bourhood of the Max-Planck-Institutes for vational experience (max. one page) time on support or development activities Astrophysics and for Extraterrestrial in the area of e.g. instrumentation, opera- Physics and is only a few kilometres away In addition three letters of reference from tions support, archive/virtual observatory, from the Observatory of the Ludwig- persons familiar with your scientific work VLTI, ALMA, ELT, public relations or Maximilian University. In Chile, fellows should be sent directly to ESO before the science operations at the Observatory in have the opportunity to collaborate application deadline. Chile. with the rapidly expanding Chilean astro- nomical community in a growing partner- Applications and letters of reference shall In Chile, the fellowships are granted for ship. be submitted electronically to one year initially with an extension of [email protected] by the deadline. three additional years (four years total). We offer an attractive remuneration pack- During the first three years, the fellows age including a competitive salary (tax- Please read our list of FAQs regarding are assigned to one of the operations free), comprehensive social benefits, and fellowship applications (http://www.eso. groups on Paranal, La Silla or ALMA. Fel- provide financial support for relocating org/~mkissler/fellows_FAQ.html). lows contribute to the operations at a families. Furthermore, an expatriation al- level of 80 nights per year at the Observ- lowance as well as some other allow- Questions about the fellowships not atory and 35 days per year at the San- ances may be added. The outline of the answered by the above FAQ pages can tiago Office. During the fourth year there terms of service for Fellows provides be sent to: Markus Kissler-Patig, is no functional work and several options some more details on employment condi- Tel +498932006-244, are provided. The fellow may be hosted tions/benefits (see http://www.eso.org/ e-mail: [email protected] by a Chilean institution (and will thus have gen-fac/adm/pers/fellows.html). access to all telescopes in Chile via the Questions about the application proces Chilean observing time). Alternatively, Candidates will be notified of the results can be sent to: [email protected] she/he may choose to spend the fourth of the selection process between De- year either at ESO’s Astronomy Centre cember 2006 and February 2007. Fellow-
Three-colour image of the Tarantula Nebula in the Large Magellanic Cloud. The image is based on observations made on 10 February 2002 and 22 March 2003 with the FORS1 multi-mode instrument on ESO’s Very Large Telescope in three different narrow-band filters (centred on 485 nm, 503 nm, and 657 nm), for a total exposure time only slightly above three minutes. (ESO PR Photo 13a/06)
46 The Messenger 124 – June 2006 Announcements
Personnel Movements
1 April–30 June 2006
Arrivals Departures
Europe Europe
Andreani, Paola (I) European ARC Manager Pierfederici, Francesco (I) Software Engineer Comendador Frutos, Laura (E) Administrative Assistant Quinn, Peter (AUS) Head of Data Management and Operations Cristiani, Silvia (I) Secretary/Administrative Employee Quiros-Pacheco, Fernando (MEX) Student De Breuck, Carlos (B) APEX Support Astronomer Vossen, Gisela (D) Administrative Assistant Purchasing Duhr, Linda (NL) Secretary/Assistant Erm, Toomas (S) Electronics Engineer Gobat, Raphael (CH) Student Heissenhuber, Florian (D) Network Specialist Kiekebusch, Mario (RCH) Software Engineer Lorch, Henning (D) Software Engineer Lowery, Simon (GB) Communications Specialist Malapert, Jean-Christophe (F) Software Engineer Naets, Thomas (B) Internal Auditor Pedicelli, Silvia (I) Student Randall, Suzanna (GB) Fellow Saitta, Francesco (I) Student Shida, Raquel Yumi (BR) Student Toft, Sune (DK) Fellow
Chile Chile
Andersson Lundgren, Andreas (S) Operations Astronomer Borissova, Jordanka (BG) Astronomer Gil, Carla (P) Fellow Dall, Thomas (DK) Fellow Herrera, Leonardo (RCH) Electronic Engineer Del Burgo, Stephan (F) Optical Engineer Jimenez, Nestor (RCH) Telescope Instruments Operator Jakoboski, Julie (USA) Student Le Bouquin, Jean Baptiste (F) Fellow Saldias, Christian (RCH) System Administrator Monaco, Lorenzo (I) Fellow Morell, Merilio (RCH) Telescope Instruments Operator Nuernberger, Dieter (D) Operations Astronomer Reveret, Vincent (F) Operations Astronomer Sana, Hugues (B) Fellow Valdes, Guillermo (RCH) Software Engineer Wright, Andrew (GB) Network/Communications Specialist
List of Proceedings from the ESO Astrophysics Symposia
Volume Title Editors (foreseen for August) 2006 Chemical Abundances and Mixing in Stars in the Milky Way Sofia Randich, Luca Pasquini and its Satellites 2006 Planetary Nebulae Beyond the Milky Way Letizia Stanghellini, Jeremy R. Walsh, Nigel G. Douglas 2005 Growing Black Holes: Accretion in a Cosmological Context Andrea Merloni, Sergei Nayakshin, Rashid A. Sunyaev 2005 High Resolution Infrared Spectroscopy in Astronomy Hans-Ulrich Käufl, Ralf Siebenmorgen, Alan F. M. Moorwood 2005 Multiwavelength Mapping of Galaxy Formation and Evolution Alvio Renzini, Ralf Bender 2005 Science with Adaptive Optics Wolfgang Brandner, Markus Kasper 16/2003 Astronomy, Cosmology and Fundamental Physics Peter A. Shaver, Luigi Di Lella, Alvaro Giménez 15/2004 Toward an International Virtual Observatory Peter J. Quinn, Krzysztof M. Górski 14/2003 Extragalactic Globular Cluster Systems Markus Kissler-Patig 13/2003 From Twilight to Highlight: The Physics of Supernovae Wolfgang Hillebrandt, Bruno Leibundgut 12/2003 The Mass of Galaxies at Low and High Redshift Ralf Bender, Alvio Renzini 11/2003 Lighthouses of the Universe: The Most Luminous Celestial Objects Marat Gilfanov, Rashid A. Sunyaev, Eugene Churazov and Their Use for Cosmology 10/2003 Scientific Drivers for ESO Future VLT/VLTI Instrumentation Jacqueline Bergeron, Guy Monnet 9/2003 The Origin of Stars and Planets: The VLT View João F. Alves, Mark J. McCaughrean 8/2003 Gamma-Ray Bursts in the Afterglow Era Enrico Costa, Filippo Frontera, Jens Hjorth 7/2003 Deep Fields Stefano Cristiani, Alvio Renzini, Robert E. Williams 6/2003 Mining the Sky Anthony J. Banday, Saleem Zaroubi, Matthias Bartelmann
The Messenger 124 – June 2006 47 ESO is the European Organisation for Contents Astronomical Research in the Southern Hemisphere. Whilst the Headquarters Telescopes and Instrumentation (comprising the scientific, technical and H.-U. Käufl et al. – CRIRES: Commissioning of the MACAO Adaptive Optics administrative centre of the organisa- Module and General Status Report 2 tion) are located in Garching near R. Bacon et al. – Probing Unexplored Territories with MUSE: Munich, Germany, ESO operates three a Second-Generation Instrument for the VLT 5 observational sites in the Chilean Ata- G. Marconi et al. – New, Efficient High-Resolution Red VPH Grisms in VIMOS 11 cama desert. The Very Large Telescope R. Güsten et al. – The Atacama Pathfinder EXperiment 12 (VLT), is located on Paranal, a 2 600 m T. Wilson – ALMA News 18 high mountain south of Antofagasta. At A. Moorwood – The 2006 SPIE Symposium on Astronomical Telescopes and La Silla, 600 km north of Santiago de Instrumentation – Observing the Universe from Ground and Space 19 Chile at 2 400 m altitude, ESO operates several medium-sized optical tele Reports from Observers scopes. The third site is the 5 000 m A. Zijlstra et al. – The Compact Discs of Post-AGB stars 21 high Llano de Chajnantor, near San M. I. Wilkinson et al. – Probing the Dark Matter Content of Pedro de Atacama. Here a new submil- Local Group Dwarf Spheroidal Galaxies with FLAMES 25 limetre telescope (APEX) is in opera- A Three-Planet Extrasolar System 29 tion, and a giant array of 12-m submil- D. Proust et al. – The Shapley Supercluster: the Largest Matter Concentration limetre antennas (ALMA) is under in the Local Universe 30 development. Over 1600 proposals are F. Courbin et al. – The Host Galaxies of the Brightest Quasars: made each year for the use of the ESO Gas-Rich Galaxies, Mergers, and Young Stars 32 telescopes. Other Astronomical News The ESO MESSENGER is published four R. M. West – André B. Muller (25.9.1918–1.4.2006) 37 times a year: normally in March, June, C. Madsen – Finnish Parliamentary Committee at ESO Headquarters 38 September and December. ESO also T. Richtler, S. S. Larsen – Report on the ESO-FONDAP Conference on publishes Conference Proceedings and Globular Clusters – Guides to Galaxies 39 other material connected to its activi- Fellows at ESO – A. Lundgren, V. Reveret 41 ties. Press Releases inform the media C. Madsen – Walloon Space Days 42 about particular events. For further D. Pierce-Price – Schoolchildren Worldwide Compete to “Catch a Star!” 43 information, contact the ESO Public S. Uttenthaler et al. – A Solar Eclipse Expedition to Turkey 44 Affairs Department at the following ad- dress: Announcements 2007 ESO Instrument Calibration Workshop 45 ESO Headquarters Towards the European Extremely Large Telescope 45 Karl-Schwarzschild-Straße 2 ESO Fellowship Programme 2006/2007 46 85748 Garching bei München Personnel Movements 47 Germany List of Proceedings from the ESO Astrophysics Symposia 47 Phone +498932006-0 Fax +49893202362 [email protected] www.eso.org
The ESO Messenger: Editor: Peter Shaver Technical editor: Jutta Boxheimer www.eso.org/messenger/
Printed by Peschke Druck Schatzbogen 35 81805 München Germany Front Cover Picture: Spiral Galaxy NGC 4565 © ESO 2006 This image is based on data obtained by FORS1 and FORS2 at the VLT. The data ISSN 0722-6691 were extracted from the ESO Science Archive and further processed by Henri Boffin (ESO). They are based on exposures made through four optical filters – B, V, R and I. More information can be found in ESO PR Photo 24a/05.