Science Highlights

Light Echoes of Ancient Supernovae in the Large Magellanic Cloud

Armin Rest, Nicholas Suntzeff, Chris Smith, Knut Olsen (NOAO) & the SuperMACHO Collaboration

n the past decade, light echoes have been discovered further out, and fainter, than previously detected. In these around some nearby extragalactic supernovae well after images, white represents flux enhancements in the 2002 and the explosion, most notably the light echoes from SN 2004 images, and black in the 2001 image. Faint echo arcs 1987A.I However, no light echoes of historical SNe of Galactic can be seen as far out as 6.6 arcmin and 7.3 arcmin from the or extragalactic origin have been discovered to date. explosion site, or 0.9 and 1.1 kpc in front of SN 1987A.

Beside the SN 1987A light echoes, we found a number of other very faint linear structures that had high proper motions, generally superluminal. However, these echoes were spatially in a very different location than the SN 1987A echoes. We suspected that these were light echoes from pre- historical supernovae. The left panel of figure 2 shows such a light echo candidate. In order to find the source of the light echoes, we fit each light echo segment with a straight

Figure 1. Light echoes from SN 1987A.

In the SuperMACHO project, we have imaged the bar of the Large Magellanic Cloud (LMC) repeatedly and used an automated pipeline to subtract point-spread function matched template images from the recent epoch images. The resulting difference images are remarkably clean of the constant stellar background and are ideal for searching for variable objects. Using these difference images, we have mapped the extensive light echo complex around SN 1987A. The image in Figure 1 reveals echoes of SN 1987A NOAO-NSO 85 Newsletter

Figure 2. Candidate light echoes from pre-historical super- Figure 3. Spectrum of the brightest echo from light echo novae (left). These are extrapolated backward (right) to group LE2 (black line) compared with supernovae spectra of determine the positional origin of the light echoes. different types (light lines).

continued

March 2006 3 NOAO-NSO Newsletter 85 4 image of the lens galaxy, rendering detailed study of the the of study detailed rendering galaxy, lens the of image the overwhelms often images quasar lensed of light the and history, heterogeneous (and discovery serendipitous!) usually an by lensed quasar distant galaxy. lenses elliptical Quasar have intervening an a extremely involve band optical the in lensing strong galaxy-scale of examples known the of Most systems. lens uenv rmat (Ns Mtesn t a. 1985), al. LMC the in SNRs et. youngest six the of three Mathewson also are which (SNRs; remnants known of supernova positions the to arcminutes origins of echo within one correspond unidentified well-defined complexes, three The echo four 1987A. the SN is of to which origins point the as vectors positions extrapolated The backward. extrapolated Theand line. given isapparent the proper motion by vector Light of Echoes Ancient Supernovae continued S has historically been limited by the rarity of confirmed confirmed of rarity the by limited been historically has However, the power scientific of lensing to problem this tackle Binney (e.g. bright astro-ph/0412089). 2004, controversy Kochanek in astro-ph/0310219; 2003, of matter subject the dark of remains role ellipticals the and tracers, their since kinematic valuable, direct through observed be particularly generally cannot curves is rotation galaxies elliptical lensing Strong by galaxies. of clusters and galaxies in mass of (Rest et. al. 2005). al. et. (Rest Nature in published was paper sky. discovery Our southern the in star brightest third the been have would and V=-0.5 reached have would about and years. 400 between 800 Such Type-Ia supernovae on based echoes and position motion, their and we find ages from Type-Ia echoes in supernovae the LMC. Welight derive ages can for the scattered are structures detected newly proper apparent high these we the that conclude light, diffuse of variable motions the and positional SNRs the young Given with match spectra. emission X-ray the from Type-Ialikely events based on derived abundances chemical threeTheseareSNRs thethatthree precisely areas classified 1995). al. et. (Hughes Science Highlights of light paths by massive objects, is both a beautiful beautiful a measurement bending the for both tool powerful a is and phenomenon objects, dramatic massive by the paths light of lensing, gravitational trong March 2006 The SLACS Survey: ABumper Crop of New Gravitational Lenses Adam Bolton (Harvard/Smithsonian CfA) (Harvard/Smithsonian Bolton Adam

n fimy sals wehr hy ee oe olpe or collapse core supernova, were the of they explosions. light whether thermonuclear the establish of firmly spectra and obtain would we to found, able are be arcs such If Kepler, 1006/Lupus. of events and Tycho, Type-Ia probable the as in such supernovae Galaxy, historical our recent in arcs echo similar find to principle, in possible, be should It supernovae. ancient from light seeing are we that doubt a beyond proves spectrum The time. out at this ruled completely be but Type cannot Ia, the than fit worse noticeably a produces panel) (middle Ibc Type the of spectrum The panel). (lower Ia Type over-luminous an observed the fit (upper not panel). spectrum Thebest fitdo weis obtain for SN 1991T,spectra II Type that find We SNe various types. of spectra dust-scattered and integrated fit We 3. of figure in shown light echo the spectrum S/N high relatively the extracted careful we With reduction, segments. echo the along aligned slitlets with GMOS using South Gemini with LE2 group echo light echo from brightest the of spectrum a obtained recently have We published. The SLACS lens sample is uniformly selected selected uniformly is be sample to lens still SLACS 10 The additional published. an with galaxies, aligned two of composed lenses, gravitational strong unknown previously 19 discovered also have We survey. lens spectroscopic of type this implemented successfully has astro-ph/0601628) submitted, ApJ, 2006, al. et Koopmans astro-ph/0512044; press, in ApJ, 2006, al. et Treu astro-ph/0511453; 703, 638, ApJ, 2006, al. et Bolton Survey: or SLACS, ACS, Lens Sloan (The group our component, (SDSS), spectroscopic massive Survey its Sky and Digital Sloan the of advent the With galaxies. of lower-redshift spectra the in lines emission the suggested in lenses 139) such of numbers 278, significant detecting of MNRAS, possibility 1996 al. et (Warren 1996 in 0047-2808 lens galaxy-galaxy the of discovery The surveys. imaging in identify to difficult more much are but numerous quite be should principle in another, by lensed of one galaxy consisting lenses, Strong difficult. quite latter uvy, i a erh o high-redshift for search a via surveys, spectroscopic

continued

Science Highlights

The SLACS Survey continued

(Bolton et al. 2004, AJ, 127, 1860), with relatively bright lens galaxies that are amenable to detailed photometric and dynamical study.

Central to the success of our survey has been the use of the Hubble Space Telescope (HST) and the Gemini GMOS-N Integral Field Unit (IFU). With HST, we obtain imaging of these new lenses at the highest possible spatial resolution (figure 1), thus permitting detailed morphological and photometric measurement of the lens galaxy, along with mass modeling using the lensed images of the background galaxies. The three-dimensional (two spatial plus one wavelength) capability of the GMOS IFU then allows us to confirm the coincidence of the high-redshift line emission Figure 1. HST ACS-WFC imaging of eight newly discovered grav- detected by SDSS with the lensed images seen by HST itational lenses from the SLACS survey. Credit: NASA, ESA, and cement the lensing interpretation over other possible A. Bolton (Harvard-Smithsonian CfA) and the SLACS Team. explanations for the observed image features (figure 2). will determine the full two-dimensional stellar kinematics One of the many initial results of the SLACS Survey is of the lens galaxies. These data are related to the mass and that, within the context of simple power-law mass models, light in the lens galaxy through the Jeans equation, and the these elliptical lens galaxies show the same “conspiracy” mass profile of the lens galaxy is additionally constrained by between luminous and dark matter as disk galaxies, the lensed images. leading to an approximately constant rotational speed as a function of position within the galaxy (an “isothermal” With its 5 arcsec × 7 arcsec field of view and 0.2 arcsec spatial density profile). We will again look to ground-based sampling, the GMOS IFU is the perfect tool for spectroscopy spectroscopy with instruments such as the GMOS IFU to of galaxy-scale gravitational lenses such as the SLACS constrain more detailed models of stellar and dark-matter sample. The instrument will undoubtedly deliver many components. Deeper observations with these instruments more ground-breaking results in this field. NOAO-NSO 85 Newsletter

Figure 2. Left: HST I-band image of the gravitational lens SDSSJ0737+3216 from which a model of the lens-galaxy image has been subtracted. Center: GMOS-N IFU continuum-subtracted narrowband emission-line image at the wavelength of redshifted [OIII] λ 5007 Å emission, showing strong coincidence with the image of the lensed galaxy. Right: GMOS-N IFU narrow-band continuum image at same wavelength, showing the lensing galaxy (Bolton et al. 2006, ApJ, in press, astro-ph/0511453).

March 2006 5 NOAO-NSO Newsletter 85 6 telescope coupled with the sensitivityoftelescope thecoupled with Schmidt Curtis UM/CTIO the of view of field wide the of advantage Taking (~1 scales. scales pc) global to small from galaxies), other in (and Clouds ISM the a the of build understanding to deeper the which upon provides foundation wavelengths, other at surveys parallel with together which, Line of two galaxies nearby these survey line Emission emission- optical an (MCELS), Survey Cloud the (UM)/CTIO Magellanic completed Michigan of recently University have We populations. stellar underlying the with interaction its and energetics, its constituents, its ISM, the studying for laboratories ideal Clouds Magellanic the makes extinction and low proximity relative Their a (SMC). of images Cloud Magellanic Small cover the of portion month’s shown this as in Clouds, Magellanic the than in apparent more this is Nowhere (SNRs), supershells. gigantic and superbubbles, remnants supernova (SNe), supernovae (PNe), nebulae regions, HII planetary and winds, stellar gas with ambient dust the of interaction complex and dynamic a rather but gas, with stars (lower image) and with with and image) (lower stars with cover the on color full in shown SMC of the that as such images, mosaic large into images the all assembled We have to ISM. the from emission us!) for of diffuse extent faint the full the reveal contaminant the (a from to stars images the primarily of most use subtract we which bands, continuum green and red matched in images obtained also we images, line emission- these to 6731 addition In Å. to Hα, [O Å, III] λ5007 and [S II] λ6716, corresponding bands Clouds in narrow both mapped have we CCD, 2K × 2K a T Science Highlights The Magellanic Cloud Emission Line Survey (MCELS) to be a quiescent distribution of distribution quiescent a be to thought longer no is galaxies (ISM) of medium interstellar he March 2006 Chris Smith, Sean Points(NOAO) Sean College) Smith, (Middlebury &Frank Winkler Chris

images taken by the MCELSsurvey. the by taken images 1,500 than more from assembled Cloud Magellanic Large the of mosaic A 1. Figure for both our analysis and the public public the release. data and analysis our both for and global assessment quality in preparation calibration flux final currently undergoing are and 1996, in beginning period five-year a been roughly have over data taken The 2). (figure table inset other the in given are observations the and of details Specific effects. instrumental problems flat-fielding different regions of the detector, four to help eliminate in times, more or eight sampled was spot Each galaxies. both of content gaseous the of SMC--most the of degrees square 15 and LMC the of degrees square degrees 64 including square sky, of 79 approximately total a cover of observation MCELS The 1). (figure here Large Cloud (LMC) the Magellanic mosaic shown and (top), subtracted stars a relatively small group, and although although and group, small relatively a MCELS has been a by large undertaking shells. as supergiant and superbubbles such structures large-scale as well as SNRs, and PNe as such objects scale small- of both samples studying we are driven emission. With this information excited emission from photoionization- ratio be can shock-used to differentiate II]/Hα [S the example, For emission. the driving are that the processes physical about information provides also ratios emission-line through together lines emission three the Using fluxes. emission-line the measure more accurately to able are we transients), find to SuperMACHO and surveys ESSENCE like time-domain by used same image- (the from the images continuum stellar digital the remove to techniques subtraction advanced Using continued Science Highlights

MCELS continued we are only now carrying out the final reduction, astrometric calibration and MCELS DETAILS flux calibration, it has produced many TELESCOPE: University of Michigan/CTIO 0.6/0.9m Curtis Schmidt publications based on reductions of CAMERA: SITE 2048 × 2048 CCD and STIS 2048 × 2048 CCD small portions of the full dataset. FIELD OF VIEW: 1.7 square degrees (1.3 × 1.3 degrees) Some past, and near future, scientific RESOLUTION: 2.3 arcsec/pixel, ~5 arcsec resolution highlights from MCELS include: BANDS: 3 emission lines, 2 continuum: Hα 6568/28 [S II] 6729/50 * The discovery of many new SNRs in [O III] 5012/40 the LMC based on the [S II] / Hα Continuum 6850/100 ratio diagnostic (e.g., Smith et al. Continuum 5130/155 (DDO51) 2006, in prep). COVERAGE: LMC: 64 square degrees (8 × 8 degrees) SMC: 15 square degrees (3.5 × 4.5 degrees) * The study of known and suspected Figure 2. supernova remnants in the SMC, including the discovery of several new remnants (Winkler et al. 2006, Undergraduate students have played the MCELS website and the NOAO in prep). a significant role in all phases of the Science Archive within the next year. MCELS project. At CTIO, Roger Our preliminary data release of a * An investigation into the deposition Leiton carried out dozens of nights of roughly 2 × 2 degree region including of energy and chemically-enriched observations from the Schmidt, and 30 Doradus and LMC-2 is now available material into the ISM via breakouts his contributions to the data analysis at www.ctio.noao.edu/mcels. from SNRs (Williams et al. 1999, became the subject of his bachelor’s ApJ, 514, 798). thesis at University of La Serena. A The final release of reduced data will number of students at Middlebury consist of flux calibrated combined * An examination into shell formation College in Vermont contributed to images (emission-line calibration and star formation in the superbubble many phases of the analysis, including good to better than 10 percent) with N51 D (Oey & Smedley 1998, AJ, 116, flux calibration and the development accurate astrometric solutions. The 1263). of software for combining hundreds individual reduced images will also be of images into near-seamless mosaics, available, along with the raw data and * A multi-wavelength study of the including those used for the cover calibrations. Catalogs of supernova kinematics and physical conditions image of this NOAO/NSO Newsletter, remnants, planetary nebulae, HII of the interstellar gas in the N44 the SMC. Four B.A. honors theses in regions, compact Hα sources, and superbubble (Kim et al. 1998, ApJ, physics at Middlebury have resulted other emission line objects will also be 503, 729). from their work. Many of these same produced. undergraduates are also co-authors on * A multi-wavelength investigation of one or more of the papers above. This project is funded in part by NSF the kinematics, physical structure, grants AST #9540747 and #0307613 and energization of the supergiant We are planning the release of all of the and through the Dean B. McLaughlin shell LMC-2 (Points et al. 1999, ApJ, MCELS data and data products through Fund at the University of Michigan. 518, 298). NOAO-NSO 85 Newsletter

March 2006 7 NOAO-NSO Newsletter 85 8 magnetic features does not result from relatively higher higher relatively from the result of not enhancement does brightness features the magnetic that reveals spectra computed the of Analysis filtergram. band CN wavelength shorter the in 0.96 of factor a being by average, of on lower, surprisingly slightly equal, contrast almost intensity is elements the magnetic the that filtergrams, predicts computation resulting features. The ribbon-like bright the as out stand 1, figure in in shown concentrations Magnetic filtergrams. synthetic construct to filters spectra FWHM nm 1 over the integrated and simulation magnetoconvection solar high-resolution a from snapshot single a for passbands both in spectrum the computed we hypothesis, this test To wavelength. shorter at the limit resolution telescope sensitivity better slightly function the and Planck temperature, to higher higher the of with features because magnetic fidelity of tracking allow would CN it of band whether of question the similar prompting nm, A 388.3 at exists lines employed. filters the nm of 1 FWHM) (typically passbands broad relatively the by possible made exposures short the of because reconstruction image and optics adaptive as such techniques improving image for at shows features and magnetic contrast high is advantageous method This molecule. CH the of lines by dominated is that nm), (430.5 a of G-band region spectrum the so-called the in A popular method for features is small-scale tracking imaging under (ATST) by NSO. development Telescope Solar Technology Advanced the by resolved be should but the telescopes, beyond solar are present of that reach dynamics scales spatial and on field structure magnetic the the of of predictions makes magnetoconvection, which solar of simulation realistic we a end, employ this To observationally. elements flux these track small-scale to way optimal the finding Wewith concerned telescopes. are solar of limit resolution current well the possibly below sizes with concentrations field small-scale of form the in exists flux magnetic of the fraction A substantial scales. possible smallest the to regions sunspots with active large from ranging scales, spatial all on field the to track able we have to be redistributed, is and it evolves O Science Highlights how the magnetic field in the Sun is generated, how generated, is Sun the in field magnetic the how understand to order In dynamo. solar ofthe nature the is physics solar in mysteries remaining the of ne March 2006 Synthetic CH- and CN-band Images of Solar Magnetoconvection Han Uitenbroek & Alexandra Tritschler &Alexandra Han Uitenbroek granular lanes. granular stand out as the bright, ribbon-like structures in the inter the in structures ribbon-like bright, the as out stand features Magnetic respectively. nm, 388.3 430.5 and at nm bands (right) CN and (left) CH the in filtergrams Synthetic ehd o rc salsae antc ed bcue of because fields wavelength. longer magnetic at the sensitivity detector higher small-scale track to method two the in contrast molecular bands, similar imaging in the CH the band is still the given preferred that, conclude We band. wavelength shorter the in temperature by molecular intensity the independent, raise preferentially would caused which two enhancement, brightening the to in contrast wavelength in contrasts bands, similar is the in resulting mechanism evacuation magnetic of brightening-through- This filtergrams. in the elements seen enhancements intensity characteristic leading higher, the be to to intensity The filter integrated the causes concentrations. field passband filter in the lines absorption of magnetic spectral weakening strong look into that sight of down lines for lines spectral molecular the of a in weakening of resulting reduced, density is substantially molecules the environment, pressure lower the In height. is pressure geometric one at equal external the lower than gas substantially internal the the surroundings, of pressure non-magnetic gas the with concentration field magnetic a inside pressures gas and magnetic of sum the Tobalance concentration. flux magnetic of highest of regions the evacuation butpartial the from temperatures,

- Science Highlights

Direct Measurements of Zonal Winds on Mars through

Ultra-High-Resolution Observations of CO2 Guido Sonnabend & Daniel Wirtz (University of Cologne)

During the first week of December 2005, we successfully operated the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) at the McMath-Pierce Solar Telescope to observe CO2 emission and absorption features in the 10 µm wavelength range on Mars. While this absorption occurs in the lowest few kilometers of the atmosphere, the emission originates in a thin layer at around 70 km. Thus frequency shifts in the line positions between absorption and emission can be used to calculate wind speeds in the high atmosphere. Figure 2. Set-up scheme of the optical receiver: laser (LO) Our heterodyne instrument consists of an optical receiver and signal (switchable between telescope and two loads and common back-end electronics including an in-house at known temperature for calibration) are combined by a built Acousto-Optical Spectrometer (AOS). Inside the diplexer and focused on the detector. After filtering and receiver, the monomode emission from a local oscillator amplification, the frequency analysis is carried out using an (LO) is superimposed with the infrared (IR) radiation AOS (not depicted). coming from the telescope and detected on a fast Mercury Cadmium Telluride (MCT) detector. With this method, the spectral information is shifted from the mid-IR to the 3 × 107 can be achieved, which corresponds to 1 MHz or 10 radio range, allowing amplification, filtering, and frequency m/s at a wavelength of 10 µm. The band width is temporarily analysis of the signal using a standard back-end. A photo limited to 1.4 GHz and will be expanded to twice that value of the setup at the McMath-Pierce on Kitt Peak is shown in in the near future. The sensitivity of our instrument is

figure 1 and a schematic of the set-up is shown in figure 2. comparable to common CO2 laser systems.

The receiver employs tunable Quantum-Cascade Lasers Various models for Martian atmospheric dynamics recently (QCL) as local oscillators which in principle allow operation became available, due primarily to the high number of space between 8 and 17 µm wavelength. A spectral resolution of missions to the red planet. However, observations of winds in particular are missing. This is not only interesting for Mars but also important in general for planetary atmospheres (Venus, Earth, Titan, etc.). The Mars Global Surveyor Thermal Emission Spectrometer (MGS/TES) provided data to predict zonal winds up to a height of approximately 65 km, for example. The zonal wind fields are estimated from the temperature field as a function of height, latitude, and seasons of the Martian atmosphere.

Information about Martian zonal winds in higher altitudes can be directly retrieved by simultaneous detection of

CO2 absorption in the lower atmosphere (< 5 km) and NOAO-NSO 85 Newsletter

CO2 emission in the upper atmosphere (60–80 km). The

non-LTE CO2 emission lines (line width approximately 40 MHz) generated in the Martian mesosphere can only be resolved with high spectral resolution spectroscopy in the mid-IR region. Figure 1. THIS at the McMath-Pierce main telescope: the optical receiver (cubic aluminum structure on the left) and THIS is ideally suited to perform these measurements. The back-end electronics (19-inch rack on the right), including Doppler width of the emission feature yields information the Acousto-Optical Spectrometer (AOS). about the temperature of the atmospheric region where the continued

March 2006 9 NOAO-NSO Newsletter 85 10 a number of positions on the Martian disk to get an an get to disk Martian the on observed positions systematically we of run, number 2005 a the During TES. MGS/ from derived models with agreement good in is value measured The 3). (figure 2003 in McMath-Pierce the at run observing an during achieved was result A proof of principle models. by various made to predictions compared be will results These velocities. wind zonal of center positions of these two lines provides observation direct the much broader CO broader much the on superimposed is line emission The place. takes emission Direct Measurements of Zonal Winds on Mars continued Figure 3. Left: CO Left: 3. Figure the higher atmosphere. atmosphere. higher the suggesting an altitude of 60-80 km as the origin of the the absorption line of of 7.5 origin MHz the is the of center the most from likely peak as emission caused the of by offset km (FWHM),The zonal line. wind in MHz 60-80 4.0 of ± altitude MHz an 42 suggesting be to determined was peak emission of the width The respectively. graphs, right bottom and top the in separated shown spectra martian and telluric the yields line) heavy (single fit combined The absorption. ozone telluric by contaminated highly and resolution MHz 4 a to binned sideband, double are spectra 1037.4 The cm-1. Science Highlights March 2006 2 P(30) absorption and emission line at at line emission and absorption P(30) 2 absorption line and the offset of the the of offset the and line absorption

observed (L observed we season the during field wind global the of impression goal will be the detection of cold interstellar H interstellar main cold of detection The the be will goal SOFIA. observatory airborne stratospheric the on operated be to THIS for plans long-term are There 4. figure in shown is spectrum example unprocessed Optics, 41, 2978 (2002). Optics, 435, 1181 & Schieder, Appl. Wirtz, (2005) and Sonnabend, A&A, al., et Sonnabend reading: further for Suggestions planned. are disks, or proto-planetary stars as well as atmospheres, planetary of observations Until further SOFIA becomes operational, moderately hot IR sources, at wavelengths around 17 around wavelengths at sources, IR hot moderately exact frequencies is ongoing. the frequencies of exact Analysis MHz. 1 of resolution full at shown are 959.4 on The spectra Mars. cm-1 latitude at 45° northern iue . CO 4. Figure S =335). Data analysis is still ongoing, but an an but ongoing, still is analysis Data =335). 2 P(2) absorption and emission line at at line emission and absorption P(2) 2 , against against , µ m. m.