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CONTENTS

Program Main 6 Parallel sessions 7

Abstracts Talks 8 Posters 23

Participants list 52

3 4 5 MAIN PROGRAM

Wednesday, May 23

14.00 – 14.05 Short welcome 14.00 – 14.30 Thijs van der Hulst Tracing galaxy evolution with HI 14.30 – 14.50 Neeraj Gupta Tracing the evolution of cold gas in galaxies using 21-cm absorption 14.50 – 15.10 Lex Kaper Resolving stellar populations with the E-ELT 15.10 – 15.30 Erwin de Blok Dark Matter and ISM in the THINGS galaxies 15.30 – 15.50 Steven Rieder Evolution of globular clusters in dark matter haloes 15:50 - 16:20 Coffee Break 16.20 – 16.40 Poster Session 16.40 – 17.00 Leon Koopmans Making Dark-Matter Substructure Visible 17.00 – 17.20 Robyn Sanderson Weighing dark halos with tidal shells 17.20 – 17.40 Frank Israel Ionized carbon in the Local Group ISM 17.40 – 18.00 Floris van der Tak The first results of the Herschel-HIFI mission 18.00 – 20.00 Dinner 20.00 – 21.00 Evening Discussion

Thursday, May 24

09.00 – 09.30 Rober Laing ALMA: Recent Progress and Early Science 09.30 – 09.50 Pamela Klaasen ALMA in the Netherlands 09.50 – 10.10 Peter Roelfsema SAFARI New views on star formation with Herschel: Cores and filaments in the 10.10 – 10.30 Nick Cox Chamaeleon and Musca dark clouds 10.30 – 11.00 Coffee Break 11.00 – 11.20 Poster Session 11.20 – 11.45 Bernhard Brandl Science and Technology of METIS for the E-ELT 11.45 – 12.10 Scott Trager WEAVE and 4MOST: The next generation spectroscopic survey instruments 12.10 – 12.30 Adam Deller mJIVE-20: Imaging 10,000 faint sources with VLBI 12.30 – 13.30 Lunch 13. 30 – 16.00 Social Program 16.00 – 16.30 Coffee Parallel Sessions (details on next page) 16.30 – 18.00 Session A Session B Session C 18.00 – 20.00 Dinner 20.00 – 21.00 Klaas van Berkel – Astronomy & Propaganda: some historical reflections on the use and abuse of science

Friday, May 25

09.00 – 09.30 Michael Wise Next Generation Radio Astronomy with LOFAR 09.30 – 09.50 Peeyush Prasad All sky Calibration and Imaging for the AARTFAAC project 09.50 – 10.10 Roy Smits First results from the Large European Array for Pulsars 10.10 – 10.30 Ilse van Bemmel Renewable science with EMMA 10.30 – 11.00 Coffee Break 11.00 – 11.20 Marijke Haverkorn Direct imaging of interstellar magnetized turbulence 11.25 – 11.50 Gijs Mulders The initial conditions for planet formation 11.50 – 12.10 Phil Uttley X-ray reverberation mapping of black holes 12.10 – 12.30 Rob Rutten Progress in 50 years of chromosphere research at Utrecht 12.30 – 13.30 Lunch End of Conference

6 PARALLEL SESSIONS PROGRAM

Session A

16.30 – 16.45 Jeroen Bédorf Graphics Processing Units applied to astrophysics 16.45 – 17.00 Amin Aminaei Lunar Radio explorer: An Experiment for Radio Observations on the Moon 17.00 – 17.15 Shoko Jin The curious case of the stellar stream in Leo 17.15 – 17.30 Thomas de Boer The star formation and chemical evolution history of the Fornax dSph 17.30 – 17.45 Bertrand Lemasle The puzzling chemical evolution of the Carina dSph galaxy from VLT/FLAMES spectroscopy 17.45 – 18.00 David Sobral 11 Gyr Evolution of Star-forming galaxies: the HiZELS/H-alpha view

Session B

16.30 – 16.45 Yuri Cavecchi Magnetically confined thermonuclear explosions as probes of dense matter 16.45 – 17.00 Mikkel Nielsen Obscuration of supersoft X-ray sources in circumbinary material - A way to hide type Ia supernova progenitors? 17.00 – 17.15 Thijs Coenen The first LOFAR pulsar surveys 17.15 – 17.30 Ke Wang A Tale of the “Snake” Nebula: Star 17.30 – 17.45 Ben de Vries Formation seeds grow differentially cometary dust in the planetary belts of β Pictoris

Session C

16.30 – 16.45 Pim Schellart Measuring cosmic rays with LOFAR 16.45 – 17.00 Maura Pilia AGILE observations of ‘soft’ gamma-ray pulsars 17.00 – 17.15 Jun Yang A Decelerating Jet in XTE J1752-223 17.15 – 17.30 Lennart van Haaften The population of ultracompact X-ray binaries in the Galactic Bulge 17.30 – 17.45 Caroline D'Angelo Observable QPOs Produced by Steep Pulse Profiles in Magnetar Flares 17.45 – 18.00 Silvia Toonen Binary population synthesis and SNIa rates

7 ABSTRACTS – TALKS

Graphics Processing Units applied to astrophysics Jeroen Bédorf Leiden Observatory, Leiden University

In this talk I will present different special written high performance simulation codes. These codes are specifically tailored for astrophysics and make use of the Graphics Processing Unit (GPU). The codes form the first half of the talk, the second half will focus on applications and results obtained with these special simulation codes, for example the results of a wide range of galaxy merger simulations using different mass ratios.

Magnetically Confined Thermonuclear Explosions as Probes of Dense Matter Yuri Cavecchi Leiden Observatory, Leiden University

Type I bursts are thermonuclear explosions on the surface of accreting Neutron Stars (NSs). Sometimes the temperature of the burning surface is not homogeneous; since the star is rotating, this translates into the detection of pulsations during the bursts. The frequencies of such pulsations, known as burst oscillations, are within few Hz of the spin frequencies of the stars. Knowing the spin period of NSs is a bridge to the study of the dense matter equation of state and gravitational waves; therefore knowing precisely how the oscillations are generated is of vital importance since this would allow us to measure the spin of many NSs where a direct measure is not possible. However, even though burst oscillations have been observed for years now, there is as yet no accepted model to explain the mechanism behind this intriguing phenomenon. Last year a new pulsar was discovered that is the first case ever where every model can be excluded but one: magnetic confinement.

The first LOFAR pulsar surveys Thijs Coenen Astronomical Institute 'Anton Pannekoek', University of Amsterdam

As part of LOFAR commissioning we are performing several pilot pulsar surveys in order to characterize the system and inform a forthcoming deep survey of the entire northern hemisphere, which is expected to discover hundreds of pulsars. Here we present the results of the first LOFAR pulsar search, the LOFAR Pilot Pulsar Survey. This is the first pulsar survey to use a digital aperture array, similar to what will be available in the Square Kilometer Array. This shallow survey has observed a quarter of the sky and, with roughly a third of the data processing complete, we have re-detected several tens of known pulsars, independently discovered one new pulsar, and can place a limit on the rate of fast radio transients in general. I will also present the status of the second LOFAR pulsar search, the LOFAR Tied Array Survey, which provides a tenfold increase in sensitivity over our initial pilot survey.

8 The star formation and chemical evolution history of the Fornax dSph Thomas de Boer Kapteyn Astronomical Institute, University of Groningen

In this talk, I will present the detailed star formation history of the Fornax dwarf spheroidal galaxy, from wide-field photometry of resolved stars. the star formation history of Fornax is determined by combining accurate Colour-magnitude Diagrams with detailed spectroscopic information of RGB stars, to obtain accurate ages for individual stellar populations. We find that Fornax has experienced a complex, extended evolutionary history with multiple periods of star formation activity. A clear gradient with age and metallicity is observed with radius in Fornax, with younger, more metal-rich stars found more towards the centre. The star formation history is used to determine accurate age estimates for individual RGB stars, for which spectroscopic abundances are known. The resulting age-metallicity relation for individual stars in Fornax shows clear effects of different star formation periods, with a different slope at different ages, linked to distinct features in the star formation history and Colour-Magnitude diagrams. Furthermore, the temporal evolution of alpha- element abundances shows clear effects of age, and allows us to determine the chemical evolution timescale in the Fornax dwarf galaxy.

Cometary dust in the planetary belts of β Pictoris Ben de Vries Institute of Astronomy, Katholieke Universiteit Leuven

The discovery of more than 600 exo-planets in the past two decades has shown an amazing diversity in the properties of planetary systems. The origin of this diversity and the way the Solar System fits in must be understood by studying young systems in which planet formation is ongoing, and by comparing the properties of these young systems with the historic records of the formation of the Solar System as recorded in e.g. asteroids and comets. Strong evidence that gas-phase condensation produces Mg2SiO4, comes from observations of crystalline olivine grains in evolved cool red giants. In another study we have detected the 69 μm crystalline olivine band in several red giants and the wavelength and band shape of the resonance are in agreement with pure Mg2SiO4. In contrast, Solar System comets such as Wild 2 and chondritic meteorites show a small but significant fraction of Fe in the crystalline olivine of ∼1 per cent. β Pictoris is a young (12 Myr) main-sequence star surrounded by at least one planet at a distance of ∼10 AU, and a dusty debris disk created by catastrophic collisions of planetesimals. We have detected the 69 μm band in a HERSCHEL- PACS Range Scan of β Pictoris. Modeling this band gives an Fe/Mg ratio of 0.01 and constrains the location of the crystalline olivine to 8-16 AU. The crystalline olivine grains are probably produced by collisions between planetesimals in the known belts at 6 and 16 AU. The composition of the crystalline olivine is strikingly similar to that of Solar System bodies like comets, IDPs and meteorites. But an Fe/Mg ratio of 0.01 is not compatible with crystalline olivine grains produced through gas phase condensation, meaning that the crystalline olivine in β Pictoris must come from another source, similar to the one in our Solar System.

9 The initial conditions of planet formation Gijs Mulders Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Protoplanetary disks represent the initial conditions of planet formation, and to understand how planets form we need to understand the physical processes within these disks. I will show how their vertical structure can be derived from unresolved spectral energy distributions, and what this means for the underlying disk physics. I will do this for samples of disks around different stars, ranging from low-mass brown dwarfs to high-mass Herbig Ae/Be stars. No significant variations in disk properties or physics are found, and I will show how this leads to the conclusion that the initial conditions of planet formation are independent of the mass of the central star.

Obscuration of supersoft X-ray sources in circumbinary material - A way to hide type Ia supernova progenitors? Mikkel Nielsen Astronomy Department, Radboud University Nijmegen

Supernovae type Ia are of crucial importance to cosmology, as well as to the dynamics and chemical composition of galaxies. However, despite decades of intensive research the nature of the progenitor systems of these important astrophysical objects remains unclear. It is commonly assumed that the exploding object is a white dwarf close to the Chandrasekhar mass that has accreted material from a companion. Two scenarios are normally considered: the merger of two white dwarfs (the double degenerate scenario), and a white dwarf accreting from a non-degenerate companion (the single degenerate scenario). In the latter case the progenitor is expected to emit supersoft X- rays for an extended period before exploding. However, observations have been unable to find such systems in large enough numbers to account for the supernova Ia rate. This may mean that the systems are simply not there, and that the single degenerate progenitor channel does not contribute significantly to the supernova Ia rate. Alternatively, the systems are somehow hidden from observational view. We explore the latter option by setting up a model of a single degenerate binary that is losing mass into the circumstellar region, and find that the X-ray emission can be obscured by this material. We find upper limits to the binary separations and mass loss rates for which the system will be unobservable as a supersoft X-ray source and compare these with archival, pre-explosion observations of nearby supernovae type Ia.

The puzzling chemical evolution of the Carina dSph galaxy from VLT/FLAMES spectroscopy Bertrand Lemasle Kapteyn Astronomical Institute, University of Groningen

CMD analysis have shown for a long time that the Carina dwarf spheroidal galaxy had an unusually episodic star formation history, with active episodes of star formation separated by long periods of no star formation at all. We will present our new abundances measurements based on VLT/FLAMES spectra. They allow us to examine how the peculiar star formation history of the Carina dwarf spheroidal is reflected in the abundances of several elements and what they tell us on the chemical evolution of this galaxy.

10 Evolution of globular clusters in dark matter haloes Steven Rieder Leiden Observatory, Leiden University

I present a method to simulate star clusters in a cosmological tidal field, using the AMUSE software environment. With this method, we simulate globular clusters in the CosmoGrid cosmological environment. We use this environment as a background potential for N-body simulations of globular clusters. For two Milky Way-sized dark matter haloes in CosmoGrid, we study the mass evolution of clusters at various radial distances in order to find the effect of tidal forces caused by an evolving ΛCDM environment. This way, we determine the imprint of the halo formation history on globular clusters. We find that the mass loss rate decreases with radial distance. Also, merger events increase the clusters' mass loss rate, due to the increase in halo core mass.

First results from cosmic-ray measurements with LORA Satyendra Thoudam Astronomy Department, Radboud University Nijmegen

An air shower array LORA (the LOfar Radboud air shower Array) has been installed in the core of the LOFAR radio telescope in the Netherlands. The objective is to contribute to the measurements of cosmic-rays with LOFAR. The main purpose of LORA is to trigger the read-out of the LOFAR radio antennas to register extensive air showers initiated by cosmic-rays of energies above ~ 1016 eV. In addition, LORA also provides basic air shower parameters such as the position of the shower axis, the arrival direction, and the energy of the primary cosmic-ray. LORA started its full operation in June 2011 and during the same time, it had contributed to the first detection of cosmic-rays with LOFAR. It has now collected over 2 million cosmic-ray events. Its first science results will be presented and compared with the measurements of other cosmic-ray experiments. The results include the measurements of the charged particle lateral distribution of air showers, measurements of atmospheric attenuation coefficients, and the all-particle cosmic-ray energy spectrum. The energy spectrum is measured in the interesting energy region of ~ 1016 to 1018 eV where the transition from the Galactic to extra-galactic cosmic-rays is expected.

Science and Technology of METIS for the E-ELT Bernhard Brandl Leiden Observatory, Leiden University

The Mid-infrared E-ELT Imager and Spectrograph METIS will likely be the 3rd instrument on ESO's planned 40m E-ELT. METIS will be one of the largest investments of the Netherlands in optical/infrared astronomy. In this talk I will summarize the status of the E-ELT, the science case for METIS, and its technical concept.

11 Binary population synthesis and SNIa rates Silvia Toonen Astronomy Department, Radboud University Nijmegen

Binary population synthesis codes as SeBa, are very useful tools to study the evolution of binary stars and the processes that govern them. By comparing observed and simulated SNIa rates, we aim to constrain binary evolution processes, i.e. the common envelope (CE) phase and the efficiency of mass retention from accretion onto a white dwarf (WD). In the double degenerate scenario a SNIa event is caused by the merger of two carbon-oxygen WDs with a combined mass exceeding the Chandrasekhar mass limit. We set out to predict accurate SNIa rates, with the additional constraint that our model corresponds well to the observed population of double WDs (of all flavours and masses) as well, so implying the use of the gamma-CE instead of the alpha-CE. However, we find that both models underpredict the observed SNIa rate by a factor ~8-13. In the single degenerate scenario a SNIa event occurs when a WD accretes matter from a non-degenerate companion until the critical mass limit is reached. Theoretical rates for this scenario predicted by different groups vary over four orders of magnitude. We study the effect of the efficiency of accretion onto the WD, which is not well understood because of processes as novae and stable burning. We show that the simulated SNIa rates are significantly affected by which prescription for the mass retention efficiency is used. However, it does not explain all differences between the theoretical SNIa rate distributions, and therefore a collaboration has been initiated to compare four population synthesis codes.

New views on star formation with Herschel: cores and filaments in the Chamaeleon and Musca dark clouds Nick Cox Institute of Astronomy, Katholieke Universiteit Leuven

I will present new results on the presence and properties of cores and filaments in the Chamaeleon and Musca low-mass star forming regions. These dark clouds have been imaged at far-infrared wavelengths with Herschel as part of the Gould Belt survey. The Musca cloud is a well known large dark filament with a low star-formation efficiency, containing only one known young stellar object, but a dozen or so dense condensations. The Herschel observations have also revealed low-density striations perpendicular to the main filament. The Chamaeleon dark cloud consists of three distinct regions, with decreasing star-formation rates from Cha I, II to III. In fact, Cha III does not contain any young stellar objects but does reveal a number of dense (pre- stellar?) cold condensations detected at far-IR and sub-mm wavelengths. These results are linked to Herschel studies of cores and filaments in other nearby star forming regions.

12 Lunar Radio eXplorer, An Experiment for Radio Observations on the Moon Amin Aminaei Radboud University, Nijmegen

We present the scientific and technical aspects of Lunar radio observations using a tripole antenna and a sensitive digital receiver in a broad spectral range (10 kHz- 100MHz). This experiment, referred to as the Lunar Radio eXplorer (LRX), is a dedicated instrument selected for the ESA Lunar Lander mission (expected launch in 2018) as part of the Lunar Dust Environment and Plasma Package(L-DEPP). The Lunar Lander will essentially be a path-finder mission and address key questions to prepare for future lunar human and science missions. In addition, the LRX will open up the virtually last unexplored frequency regime below 10 MHz which is inaccessible from the earth due to a cut-off in the earth’s atmosphere. A Phase-A study on the LRX is currently performed under the supervision of the Radboud University Nijmegen. We present an overview of the key science cases the LRX will address: the study of Lunar environment, Solar and Planetary science and radio astronomy and cosmology. In the study of the Lunar environment, the LRX antenna will be used to monitor the lunar exosphere and its interaction with the Earths magnetosphere and solar wind plasma. One of the major goals, and essential for future scientific exploration of the moon, will be to measure the lunar radio background noise and to determine the limit of lunar radio observations. In addition, acting as a ground penetrating radar, the LRX would also provide significant information about the moon surface and sub-surfaces. For Solar and Planetary science the LRX aims to study solar flares and CMEs as well as observations of radio emission from planets such as Jupiter and Saturn. This will provide present- day information on the current rotation periods of these planets. The LRX antenna on the moon will be able to address a multitude of radio astronomy science cases. For example, radio bursts from ultra-high energy cosmic rays hitting the moon surface will be studied, essentially using the moon as cosmic ray detector, More importantly, placing the antenna at the Lunar south (north) pole would not only allow to observe the dark and sun-lit side of the moon simultaneously, but also provide shielding from man-made RFI while the earth is below the horizon. This will provide the stable observing conditions that are required to look for the global radio signal from atomic hydrogen produced in the early phase of the universe, before the first stars and galaxies formed; i.e. to measure the signal from the so-called “dark ages”. Finally, based on our experience with the LOFAR (Low Frequency Array) and AERA (Auger Engineering Radio Array) experiments, we review the technical details of the LRX experiment towards the future plan for a large lunar radio interferometer.

ALMA in the Netherlands Pamela Klaassen Leiden Observatory, Leiden University

The ALMA telescope is a revolutionary new telescope nearing completion in the Atacama region of Northern Chile. I will present a brief overview of the current status of the array, and what capabilities will be available for the next observing period. In anticipation of the proposal deadline in mid July, the focus of this talk will be what types of user support are available from the Allegro ALMA regional centre in Leiden, and the resources available from proposal preparation through to data reduction.

13 Observable QPOs Produced by Steep Pulse Profiles in Magnetar Flares Caroline D'Angelo Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Strong quasi-periodic oscillations observed in the tail of giant magnetar flares are frequently interpreted as evidence for global seismic oscillations (star quakes). The steeply pulsed emission profile in the tail of the flare can enhance the observed amplitude of the underlying oscillation, analogously to a beam of light oscillating in and out of the line of sight. However, I will demonstrate that for a realistic emission geometry, the observed oscillations (with rms variability of of up to 20% of the total flux) cannot be produced by the physical motion of the beam itself (that is, a direct detection of the crust's motion). Instead, the QPOs are most likely produced by modulations in the intensity of the emission, indicating a better understanding of the emission mechanism is needed.

The role of Gravitational Waves in LMXBs Brynmor Haskell Astronomical Institute 'Anton Pannekoek', University of Amsterdam

I will discuss the suggestion that Gravitational Wave emission may be setting the spin equilibrium period of Neutron Stars in LMXBs. I will first show that X-ray observations of some of these systems (in particular SAX J1808.4-3658 and XTE J1814-338) can help shed light on whether or not they are emitting gravitational waves, and discuss recent theoretical advances in the modelling of the disc/magnetosphere interaction. Finally I will discuss how X-ray data can be used to shed light on the physics of the gravitational wave driven r-mode instability in neutron stars and to constrain the equation of state of dense matter.

The curious case of the stellar stream in Leo Shoko Jin Kapteyn Astronomical Institute, University of Groningen

Leo IV and Leo V are two Milky Way dwarf galaxies separated by a mere 3 degrees on the sky, and residing in our Galaxy's halo at distances of 154 kpc and 175 kpc. The combination of their proximity to one another and similar radial velocities suggests that they are tumbling into our Galaxy in union. The detection of an overdensity of stars seeming to extend between the two dwarfs raised the intriguing question of how such a stellar stream could have formed within this scenario. However, new data that we have obtained using the Subaru telescope now suggests that the stream is a structure much closer to us than the Leo dwarf galaxies themselves. I will present these results and speculate on the possibility that the Leo stream is in fact part of the Virgo Overdensity, a stellar structure covering a region of 2000 square degrees or more on the sky, and whose origin is probably a dwarf galaxy, possibly even Sagittarius.

14 Tracing the evolution of cold gas in galaxies using 21-cm absorption Neeraj Gupta ASTRON Netherlands Institute for Radio Astronomy

Deep galaxy surveys have revealed that the global star formation rate density in the Universe peaks at 1

AGILE observations “soft”; gamma-ray pulsars Maura Pilia ASTRON Netherlands Institute for Radio Astronomy

We present the discovery and follow-up observations of emission at energies E > 30 MeV from PSR B1509-58 and PSR B1846-0258 with a simultaneous analysis of data from the Italian satellite AGILE and from Fermi. PSR B1509-58 was detected by COMPTEL up to at least 10 MeV, while EGRET reported only marginal evidence (< 4 sigma) for a weak source. AGILE detected pulsed emission from PSR B1509-58 at 6.4 sigma. The COMPTEL sharp spectral break between 10 and 30 MeV seems confirmed by AGILE point implying a cutoff at E=80 MeV. PSR B1846-0258 in the SNR Kes 75, formerly considered a standard rotation powered pulsar recently showed magnetically induced behavior. Its magnetic field is ~5E13 G, above the critical quantum field and its cutoff E = 20 MeV. Such low-energy breaks, compared to the more common GeV spectral break in gamma-ray pulsars, could be the signature of the photon splitting process inducing significant electromagnetic cascade attenuation due to the strong magnetic polar field (>1013 G). Higher magnetic field pulsars have been observed in gamma-rays by Fermi, so that a concurrence of factors has to be invoked in order to explain the soft break. With the AGILE capability of observing with good sensitivity at E > 30 MeV, we investigate these two highly magnetized pulsars as possible contributors to a new class of “soft”; gamma-ray pulsars.

15 All sky Calibration and Imaging for the AARTFAAC project Peeyush Prasad Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The AARTFAAC project aims to implement a real-time, 24x7 Radio Sky Monitor (RSM) for the LOFAR radio telescope. It will thus enable monitoring for low frequency radio transients over most of the sky locally visible to the LOFAR, at timescales ranging from milliseconds to several days. Using the six stations on the LOFAR SuperTerp, the RSM will be a zenith-pointing, transit mode instrument operating simultaneously (in a piggyback fashion), with regularly scheduled LOFAR observations. Due to correlations between all dipoles on the SuperTerp being available, the AARTFAAC RSM has an all- sky field of view. However, the calibration and imaging of the entire field of view presents its own challenges, both due to the requirement of low latencies for rapid detection, and due to observational constraints. In this presentation, we highlight some aspects of these challenges, and present our initial efforts towards the RSM implementation, with a focus on feasible calibration and imaging approaches.

Weighing dark halos with tidal shells Robyn Sanderson Kapteyn Astronomical Institute, University of Groningen

The class of tidal features around galaxies known variously as “shells”' or “umbrellas”; comprises debris that has arisen from high-mass-ratio mergers with low impact parameters. In these cases the nearly radial orbit of the impact or gives rise to a unique shape and a universal density profile for the resulting tidal debris, one that can be described by a modified version of the mathematical theory of caustics. I demonstrate how this universality allows a direct measurement the gravitational force exerted by the galaxy at the radius of a shell, given only the limited information available in two- dimensional images and line-of-sight velocities. This technique makes it possible to constrain the total mass of external galaxies at large distances from their centers where dark matter dominates the potential and, if multiple shells are present, to get a rough idea of the radial mass distribution.

First results from the Large European Array for Pulsars Roy Smits ASTRON Netherlands Institute for Radio Astronomy

In Europe, five 100-m class telescopes are being used in a collaboration to regularly observe radio pulsars with the goal of detecting gravitational waves. This is called the European Pulsar Timing Array (EPTA). Within the EPTA a new project has been launched, called the Large European Array for Pulsars (LEAP), led by Michael Kramer (MPIfR, Bonn) and Ben Stappers (University of Manchester, UK), which aims to combine all five telescopes together, creating the equivalent of a 200-meter steerable dish. As of March 2012, LEAP is observing 24 hours every month using WSRT, Lovell and Effelsberg. The first results of these observations will be presented.

16 Renewable science with EMMA Ilse van Bemmel ASTRON Netherlands Institute for Radio Astronomy

As LOFAR is demonstrating, aperture array (AA) technology is at the forefront of new developments and discoveries in radio astronomy. For the mid-frequencies, from 500 to 1500 MHz, AAs still have to prove their scientific value with respect to the existing dish technology. Their large field-of-view and high flexibility puts them in an excellent position to do so. ASTRON is dedicated to demonstrate the feasibility of AAs for science in general and SKA in particular. For the mid-frequency range it has developed EMBRACE, which has demonstrated the enormous flexibility of AA systems by observing HI and a pulsar simultaneously. In my talk I will present EMMA, which is a science capable AA instrument. At 10 times the size of EMBRACE, it is the size of a single SKA station. EMMA will be capable of a wide range of science, from local HI studies to Baryonic Acoustic Oscillations and high-redshift HI absorption. In addition, EMMA will focus on construction and operation using renewable resources as much as possible.

The 11 Gyr Evolution of Star-forming galaxies: the HiZELS/H-alpha view David Sobral Leiden Observatory, Leiden University

I will present new deep and wide narrow-band surveys undertaken with UKIRT, Subaru and the VLT; a unique combined effort to select large, robust samples of H- alpha (Ha) emitters at z=0.40, 0.84, 1.47 and 2.23 (corresponding to look-back times of 4.2, 7.0, 9.2 and 10.6 Gy) in a uniform manner over ~2 deg2 in the COSMOS and UDS fields. The deep multi-epoch Ha surveys are sensitive to Milky-Way SFRs out to z=2.2 for the first time, while the wide area and the coverage over two independent fields allows to greatly overcome cosmic variance. A total of over ~600 sources per epoch are homogeneously selected. Overall, the evolution seen in Ha is in good agreement with the evolution seen using inhomogeneous compilations of other tracers of star formation, such as FIR and UV, jointly pointing towards the bulk of the evolution in the last 11 Gy being driven by a strong luminosity/SFR increase from z~0 to z~2.2. Our uniform analysis allows to derive the Ha star formation history of the Universe, for which a simple time-parameterization is a good approximation for the last 11Gy. Both the shape and normalization of the Ha star formation history are consistent with the measurements of the stellar mass density growth, confirming that our Ha analysis traces the bulk of the formation of stars in the Universe up to z~2.2. We are also exploring the large, multi-epoch and homogeneously selected samples of Ha emitters to conduct detailed morphology, dust, clustering, environment and mass studies which are providing us with a unique view on the evolution of star-forming galaxies and what has been driving it for the past 11 Gy.

17 Dark Matter and ISM in the THINGS galaxies Erwin de Blok ASTRON Netherlands Institute for Radio Astronomy

After a short introduction about The HI Nearby Galaxy Survey, I discuss the shapes of the dark matter halo profiles derived from the kinematics of these galaxies. I compare them with the Einasto mass density profiles which have recently become popular as a description of the halos found in cosmological N-body simulations. In the second half of the talk I discuss the elocity dispersions of the HI based on high signal-to-noise stacked profiles. I show that the profiles can be decomposed in two components, associated with the warm and cold neutral medium.

A Tale of the “Snake” Nebula: Star Formation Seeds Grow Differentially Ke Wang Kapteyn Astronomical Institute, University of Groningen

The “Snake” Nebula, or the filamentary infrared dark cloud (IRDC) G11.11-0.11, is a giant molecular cloud complex that harbours a series of dense clumps capable of forming massive star clusters. Recent Herschel observations have revealed seeds of star formation --- pre- or proto-stellar objects along the IR-dark filaments. With SMA and VLA/EVLA, we zoom into the most massive clumps P1 and P6 at highest possible angular resolutions to investigate the earliest stages of massive clustered star formation. High-resolution, high-sensitivity SMA dust continuum images resolve both clumps into regularly spaced cores which show different richness in molecular line emission, indicating cylindrical collapse followed by sequential star formation. The most massive core in P1 is flattened and is associated with an ordered velocity field, likely indicating a rotating disk. Comparing results of this and other IRDCs, as well as observations of objects at later evolutionary stages, we propose an empirical picture of the early evolution of massive star formation, in which cores gain mass from the clump while protostars accrete gas from the core simultaneously.

A Decelerating Jet in XTE J1752-223 Jun Yang JIVE Joint Institute for VLBI in Europe

The X-ray transient XTE J1752-223 is a new Galactic stellar-mass black hole candidate. With the European VLBI Network (EVN) and Very Long Baseline Array (VLBA), we observed multiple transient ejecta in the radio regime during its first known X-ray outburst. The proper motion evolution in two ejecta shows direct evidence for a mildly relativistic jet, strongly decelerating at just ~100 milliarcsecond angular separation from the core, which has never been observed in black hole X-ray binaries before. At the end of the outburst sequence we detect the core of the system as it returns from its radio quenching state.

18 Progress in 50 years of chromosphere research at Utrecht Rob Rutten Lingezicht Astrophysics

In the 1960s J.M. Beckers defended his famous thesis on fine structure in the solar chromosphere at Utrecht University while J. Houtgast chased the chromospheric spectrum during eclipses. Almost no further progress was made on that most difficult solar domain until recently. Thanks to modern observing techniques and numerical simulations we now understand the formation of chromospheric diagnostics, in particular Halpha, and have identified and detailed a new type of spicules that are probably the major agent in providing mass and energy to the solar corona and wind. Ex-Utrecht solar physicists take actively part in this break-through research.

Direct imaging of interstellar magnetized turbulence Marijke Haverkorn Astronomy Department, Radboud University Nijmegen

The interstellar medium is a turbulent and magnetized, multi-phase environment. Although turbulence in the cold, neutral gas can readily be characterized through neutral-hydrogen velocity information, no such tracer was available for the magneto- ionized gas. However, we found that maps of gradients of the Stokes vector (Q, U) of Galactic synchrotron radiation are a sensitive tracer of magnetized interstellar turbulence, revealing a complex web of filaments of high gradient. Combining observations and simulations can then allow characterization of interstellar turbulence through currently unconstrained parameters such as the Mach number and magnetic field strength.

Ionized carbon in the Local Group ISM Frank Israel Leiden Observatory, Leiden University

The intensity ratio of 157.7 micron [CII] line to far-infrared conitinuum emission line intensity can be used to gauge the photo-electric heating efficiency of the ambient ISM. Galaxies in the Local Group have interstellar gas depleted in carbon by factors up to ten. They thus provide a good opportunity to investigate the behaviour of the photo- electric heating efficiency as a function of metallicity. The results are unexpected.

ALMA: Recent Progress and Early Science Robert Laing ESO

ALMA - the Atacama Large Millimetre/Sub-millimetre Array - is the most ambitious current project in ground-based astronomy. Currently under construction on a high, dry site in Northern Chile, ALMA will provide unprecedented sensitivity and resolution in the frequency range from 30 - 950 GHz. I will describe recent progress in construction and commissioning, present some results from Science Verification and Cycle 0 Early Science and preview the upcoming call for Cycle 1 proposals and the prospects for full operation.

19 Resolving stellar populations with the E-ELT Lex Kaper Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The decision to build the European Extremely Large Telescope (E-ELT) is expected to be taken in 2012. The E-ELT will be the largest optical/near-infrared telescope in the world, with a (segmented) primary mirror with a diameter of 39 meter. The large collecting area and high spatial resolution, taking advantage of adaptive optics to correct for the turbulence of the Earth's atmosphere, will provide images 16 times sharper than HST. The E-ELT will enable detailed studies of planets around other stars, the first galaxies in the Universe, super-massive black holes, and of the physical nature of dark matter and dark energy. The revolutionary 5-mirror design of the E-ELT results in a high image quality over a large field of view (up to 10' x 10'). This allows for the possibility to resolve stellar populations in a representative sample of galaxies, reaching out to the nearest giant ellipticals at the distance of the Virgo cluster. The Netherlands are closely involved in the preparation of the instrument suite of the E- ELT. I will provide a short update of the status of the E-ELT and its planned instruments, and give an impression of its large scientific potential.

Making Dark-Matter Substructure Visible Leon Koopmans Kapteyn Astronomical Institute, University of Groningen

The Cold Dark Matter paradigm leads to the prediction of numerous cold-dark-matter (CDM) substructures around galaxies. Observations of the halo of our Milky Way, however, have revealed only tens of dwarf satellites, orders of magnitude fewer than the predicted number of CDM haloes. Since 1998, this has been called “the missing satellite problem”; for which no convincing solution has yet been found. I will present recent results of our discovery of dark-matter (sub)structure beyond the Local Group through the technique of gravitational imaging. This gravitational-lens-based technique allows us to quantify the mass fraction and mass function of CDM substructure around many galaxies over cosmological distances, without them requiring baryonic content (i.e. stars or gas). I will short discuss future prospects of our method over the next decade, with 1000s of new gravitational lenses expected to be discovered (e.g. with EUCLLID, SKA, etc.), for the study of dark matter and it properties.

WEAVE and 4MOST: The next generation spectroscopic survey instruments Scott Trager Kapteyn Astronomical Institute, University of Groningen

I will discuss the design concepts for the WEAVE and 4MOST massively-multiplexed wide-field spectrograph facilities for the WHT and ESO, respectively. I will present the current state of the science cases and design studies for the two instruments, with a particular focus on those aspects of interest to the NAC community: Gaia, LOFAR, and Apertif follow-up.

20 The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA Peter Roelfsema SRON Netherlands Institute for Space Research

The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, will provide astronomers with a long awaited new window on the universe. Having a large cold telescope cooled to only 6K above absolute zero, SPICA will provide a unique environment where instruments are limited only by the cosmic background itself. A consortium of European and Canadian institutes has been established to design and implement the SpicA FAR infrared Instrument SAFARI, an imaging spectrometer designed to fully exploit this extremely low far infrared background environment provided by the SPICA observatory. SAFARI’s large instantaneous field of view combined with the extremely sensitive Transition Edge Sensing detectors will allow astronomers to very efficiently map large areas of the sky in the far infrared – in a square degree survey of 1000 hours many thousands of faint sources will be detected. A large fraction of these sources will be fully spectroscopically characterised by the instrument. Efficiently obtaining such a large number of complete spectra will be essential to address several fundamental questions in current astrophysics: how do galaxies form and evolve over cosmic time? What is the true nature of our own Milky Way? And why and where do planets like those in our own solar system come into being?

Next Generation Radio Astronomy with LOFAR Michael Wise ASTRON Netherlands Institute for Radio Astronomy

LOFAR, the Low Frequency Array, is a new and innovative radio telescope designed to open up the relatively unexplored low frequency radio regime from 30-240 MHz to a broad range of astrophysical studies. As one of the first of a new generation of radio instruments, the International LOFAR Telescope (ILT) will provide a number of unique capabilities for the astronomical community. These include wide-field, high dynamic range imaging, high time resolution, dynamic real-time system response, buffered retrospective all-sky imaging and the ability to provide multiple, simultaneous observing programs. LOFAR is moving steadily through its commissioning phase towards early science results and its first open international call for observing proposals. In this presentation, I will give an overview of the current status of the array as well as its current and planned scientific capabilities. I will also highlight a variety of recent science results obtained during the first year of commissioning and showcasing LOFAR’s scientific potential. Finally I will discuss how many of the challenges facing LOFAR, both scientific and technological, will help us prepare to build the SKA in coming years.

21 Tracing galaxy evolution with HI Thijs van der Hulst Kapteyn Astronomical Institute, University of Groningen

Studies of the HI in and around a few hundred galaxies in the nearby universe have shown that an essential ingredient in the process of galaxy formation and evolution is the balance between the acquisition of gas through merging and accretion and the depletion of gas through stripping and outflows induced by star formation and in some cases active galactic nuclei (AGN). These processes depend on environment and on cosmic time. A strong decline in star formation density in the universe over the last 7-8 Gyr indicates strong evolution. To be able to understand this evolution it is necessary to assess the balance between the acquisition and depletion of gas in many individual galaxies and many different environments over this period of cosmic time. I will review the current evidence for these processes from HI observations of galaxies and discuss the perspective of HI surveys of the local universe with the new wide field imager APERTIF on the Westerbork Synthesis Radio Telescope.

X-ray reverberation mapping of black holes Phil Uttley Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The X-ray variability from accreting stellar mass and supermassive black holes in X-ray binary systems and AGN contains encoded information about the structure and extreme conditions in the regions closest to the black hole. The fastest X-ray variations show the imprint of X-ray reverberation: time delays between variations at different energies which are due to the light travel-time from the continuum emitting region to the inner accretion disc, which reflects and reprocesses the continuum. I will show how we can use the information contained in the variable light curves to map the emitting regions closest to the black hole.

The first results of the Herschel-HIFI mission Floris van der Tak SRON Netherlands Institute for Space Research

This talk reviews the results from the first years of observations with the HIFI instrument onboard ESA's Herschel space observatory. The talk starts by outlining the goals and possibilities of far-infrared and submillimeter astronomy, the limitations of the Earth's atmosphere, and the scientific scope of the Herschel-HIFI mission. The presentation of science results from the mission follows the life cycle of gas in galaxies as grouped into five themes: Structure of the interstellar medium, First steps in interstellar chemistry, Formation of stars and planets, Solar system results and Evolved stellar envelopes. The HIFI observations paint a picture where the interstellar medium in galaxies has a mixed, rather than a layered structure; the same conclusion may hold for protoplanetary disks. In addition, the HIFI data show that exchange of matter between comets and asteroids with planets and moons plays a large role. The talk concludes with an outlook to future instrumentation in the far-infrared and submillimeter wavelength ranges.

22 ABSTRACTS – POSTERS

1. Modelling streams around our galaxy Hans Buist Kapteyn Astronomical Institute, University of Groningen

Streams around galaxies can be well described by using action-angle coordinates. In my poster I will try to explain why this is useful and what this technique offers us.

2. Persistent Topology of Gaussian Random Fields Pratyush Pranav Kapteyn Astronomical Institute, University of Groningen

The primordial fluctuation field giving rise to the structures of present day is supposed to be primarily Gaussian in nature. We study the topology of the Gaussian Random field by means of homology, a concept well known in algebraic topology. We also use the tools developed recently from persistent homology to capture the long livign structures and their properties. We apply the machinery developed to Gaussian random fields with power-law spectrum with varying power index. This is an advance over the much used genus statistics. We present our results in terms of the Betti numbers and the persistence diagram, showing that Betti numbers are able to capture differences between Gaussian random Fields in scenarios where genus is not able to differentiate between them.

3. Water and oxygen emission from protoplanetary disks: the role of X-ray radiation. Giambattista Aresu Kapteyn Astronomical Institute, University of Groningen

Oxygen fine-structure line emission at 63 micron and water rotational and ro- vibrational lines are very promising tools to study the thermal properties of protoplanetary disks. This lines are generally optically thick, thus very sensitive to the gas temperature. Using the thermo-chemical code ProDiMo we explore the contribution of the X-ray radiation to the thermal balance in the disk regions where oxygen and water emit.

23 4. Swift monitoring of the first very faint X-ray transient black hole SwiftJ1357.2-0933 Montserrat Armas Padilla Astronomical Institute 'Anton Pannekoek', University of Amsterdam

In the last decade a new population of X-ray transients has been discovered. They show anomalously low peak luminosities (2-10 keV) of 1E34 to 1E36 ergs/s. A large fraction of them is expected to harbor accreting neutron stars and black holes in binaries systems. These very faint X-ray binaries provide a new regime to study accretion onto compact objects, and therefore they can improve our understanding of accretion physics and binary evolution models. Swift J1357.2-0933 is the first very- faint X-ray transient black hole confirmed. Discovered during its outburst in January of 2011, it has been observed with several instruments. The low column density towards the source and its proximity (∼1.5 kpc) provide an exceptional opportunity to study the X-ray spectrum.

5. Methanol for probing the constancy of fundamental constants Julija Bagdonaite Department of physics and astronomy, VU Amsterdam

The question of the assumed constancy of the fundamental constants of physics, such as the fine structure constant, or the proton-to-electron mass ratio, can be addressed via quasar spectroscopy. The wavelengths of certain atomic or molecular spectral lines have well defined dependencies on the values of these constants. It means that if any drift has occurred in the distant past of the Universe, the sensitive lines would shift from their expected positions. Thus, to experimentally search for the variation, a comparison is made between highly accurate laboratory spectra and quasar spectra. Recently, rotational transitions of methanol have been identified as the most sensitive probe for the possible variation of the proton-to-electron mass ratio. Based on measurements with the Effelsberg 100-m radio telescope, a study of methanol absorption lines is presented towards the gravitational lens system PKS1830-211 at redshift 0.9.

6. The Slow temperature equilibrium behind the shock front of SN 1006 Sjors Broersen Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The historical supernova remnant SN1006 is one of the largest angular size remnants in the sky. It has many interesting features; it was for example the first supernova remnants (SNR) at which particle acceleration up to TeV energies shown to take place. The large angular size makes it a prime target to study the small scale structure of SNR's in detail. As part of the large project on SN1006 in which several European groups are contributing, we investigate the bright, northwestern emission knot with the RGS spectrograph. A previous study by Vink et al. (2003) showed that the ion temperature in this knot was as high as 500 keV while the electron temperature was only 1,5 keV, a huge difference. With about four times more data available to us, we were now able to repeat this measurement with much more precision. The results are important for the physics of temperature equilibration and particle acceleration at the shock front of SNRs.

24 7. Hunting galaxy transitions in the Hercules Supercluster Jeffrey Bout Kapteyn Astronomical Institute, University of Groningen

Within galaxy clusters the different morphologies have different spatial distributions. Early-type galaxies dominate the centers which suggests that in-falling late-type galaxies evolve. For this evolution there are multiple interaction scenarios between galaxies and the ICM, the cluster potential and other galaxies. The contributions of these scenarios are still unknown. Tracing possible transition galaxies like red spirals and flaming blue galaxies can help us in understanding galaxy evolution as a function of environment. To expand the number of found possible transition galaxies, surveys are needed that cover complete clusters, deeper and sharper than SDSS.

8. HI properties of galaxies in the Ursa Major cluster Eva Busekool Kapteyn Astronomical Institute, University of Groningen

A deep, blind survey has been done of the Ursa Major cluster using the Very Large Array in D-configuration (VLA-D). 54 Pointing were observed containing 16% of the total volume of the Ursa Major cluster. The goals of this survey are to investigate the low-mass end of the HI Mass Function (HIMF) and to study the HI morphologies and kinematics of the galaxies in this volume-limited sample. Here we report on the HIMF, which we measure down to HI masses of 107 solar masses. The characteristic volume density and the slope at the low-mass end of the HIMF of our sample are different than those of the HIMF of the recent blind surveys HI Parkes All Sky Survey (HIPASS) and Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA). The characteristic volume density is much larger, this is expected, since the Ursa Major cluster is an overdensity. The slope for this survey is approximately flat (alpha ~ -1) at the low-mass end and that is quite different than the low-mass-end slope of HIPASS and ALFALFA, which are -1.37 and -1.33 respectively. The environment seems to have an effect on the slope of the low-mass end of the HIMF.

9. The history of HH 1042: a newly discovered jet in Vela Lucas Ellerbroek Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The newly discovered jet HH 1042 in RCW 36 in the Vela C molecular cloud was observed with the new X-shooter spectrograph on the ESO Very Large Telescope, which covers the full optical to near-infrared wavelength range in one shot. The jet is driven by 08576nr292, an intermediate-mass Young Stellar Object. Using spectroscopic diagnostics, both the kinematics of and physical conditions in the jet can be measured. The kinematics contain a fossil record of the episodic outflow (and accretion) history. This can be simulated by a simple model, resulting in a two-mode sinusoidal outflow rate. The associated timescales are explained by the episodic nature of the accretion and jet-launching process.

25 10. High energy cosmic ray detections with LOFAR Arthur Corstanje Astronomy Department, Radboud University Nijmegen

Cosmic rays entering Earth's atmosphere have been detected with energies up to several times 10^20 eV. After collision with a particle in the atmosphere, secondary particles are produced in a cascade process, leading to an extensive air shower. These air showers emit short radio pulses which can be measured by LOFAR, for primary energies exceeding 10^16 eV. Since June 2011, cosmic ray air showers are measured on a regular basis. LOFAR stores its data for every antenna in a ring-buffer, that can be read out after a trigger. A scintillation (particle) detector LORA, placed inside the LOFAR core region, provides this trigger. In this poster we present details of the data analysis we use to obtain characteristics of the air shower signal. Examples of these are the distribution of pulse power on the ground, and the shape (curvature) of the incoming wavefront. These can be compared with theory and simulations, allowing to infer the primary particle type as well as the mechanism of radio emission. In the process, we produce system hardware tests, including sub-nanosecond time calibration of LOFAR stations as needed to obtain the wavefront shape.

11. Understanding dust surface chemistry in the inner Solar Nebula: a surface science approach Martina D'Angelo Zernike Institute for Advanced Materials, University of Groningen

Recent observations have revealed a rich organic chemistry (e.g. H2O, CO2, C2H2, HCN) in protoplanetary disks around young T Tauri stars, posing the question to which extent complex organic molecules can be formed in the inner warm regions of the disks. These locations of relatively higher density (1014 particles/cm3) than the outer parts of the circumstellar disk, are characterized by warm dust particles (200-400 K) and by an intense stellar radiation field (X-ray and UV) favouring the production of essential prebiotic molecules necessary for the origin of life. This poster illustrates how we plan to study such reactions on phyllosilicate platelets under astrochemically relevant conditions (0.01-0.1 mbar mixtures of H2, CO, N2, substrate at 250-350K) predicted by the thermo-chemical model ProDiMo. Typical surface science techniques, namely X-rays photoelectron spectroscopy, Reflection Absorption Infrared Spectroscopy and Temperature Programmed Desorption, will be applied to identify the reactions products, binding mechanisms and sites.

26 12. Solid state formation of hydroxylamine – towards organic chemistry in space Gleb Fedoseev Leiden Observatory, Leiden University

The observed chemical complexity in space is the cumulative outcome of gas, grain and gas-grain interactions. Recent studies indicate that a substantial part of the stable and complex species identified so far, forms on icy dust grains via non-energetic atom addition induced reaction schemes. Such reactions occur mostly at low temperatures (~10 K), i.e., in the innermost part of circumstellar clouds where newly formed molecules are shielded from radiation to a great extent by dust particles. These regions are part of collapsing envelopes feeding new stars - young stellar objects (YSOs) - and provide the original material from which comets and ultimately planets are made. Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here we present a detailed laboratory based study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final and intermediate products is presented. These results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and β-alanine) in gas phase reaction schemes.

13. Probing the planet forming regions in protoplanetary disk with CO Rosina Hein Bertelsen Kapteyn Astronomical Institute, University of Groningen

We study the emission of CO ro-vibrational lines in the Herbig Be star HD100546. We aim to determine physical properties and the spatial extention of the emission. High- spectral-resolution infrared spectra of CO ro-vibrational emission were taken with CRIRES at the VLT. From these spectra flux tables, line profiles for individual CO ro- vibrational transitions and Boltzmann plots for each vibrational transition are produced. We investigate variations in the line profile shapes and line strengths with changing position angles. Using the thermo chemical disk code ProDiMo to produce a theoretical model of HD100546, line profiles of the same CO ro-vibrational transition, line flux tables and Boltzmann plots are also produced. Through comparison with this model we aim to explore how the geometry of the disk can be evaluated from these line profiles.

27 14. W Hya as seen by Herschel Theo Khouri Astronomical Institute 'Anton Pannekoek', University of Amsterdam

W Hya is a close-by (80 parsecs away) semi-regular Asymptotic Giant Branch star (AGB), which is known to have a rather low mass loss rate ( 10^-8 solar masses/year), as derived from low excitation CO lines observed from the ground, and a high water abundance (up to 10-3), derived from observations made by satellites as ISO and ODIN. We present Herschel observations of W Hya (HIFI, PACS and SPIRE) that, together with previous ground based observations (from JCMT, APEX and SEST), contain a great deal of information on this source. The CO rotational transitions span a big range in upper level rotational quantum number (J = 1 up to 20) and give us a good overall picture of the envelope parameters. The water lines measured by Herschel allow us to constraint the water abundance of W Hya better than ever before as well as the ortho-to-para ratio. Furthermore, the molecular lines of CO, H2O and SiO isotopologues give us constraints on the isotopic ratios 13C/12C, 17O/16O, 18O/16O, 29Si/28Si and 30Si/28Si. We obtained the overall envelope physical parameters by modeling the CO lines and then tuned it by fitting the water lines. We fitted the line strengths and shapes simultaneously. By well characterizing W Hya's envelope, we improve our picture of the mass loss process in low mass loss rate AGB stars and of the CO envelope extension in these objects. By determining the ortho- and para-water abundances, we can better understand W Hya's water origin and the chemistry behind it, since the ortho-to-para ratio of gas phase water is determined by the conditions under which the molecules form. The isotopic ratios give us information about the efficiency of mixing during the third dredge-up process that occurs in AGB stars.

15. NGC1333: A Glimpse At Low-Mass Protostars Through Sub-mm Spectroscopy Evgenia Koumpia Kapteyn Astronomical Institute, University of Groningen. SRON

We study the physical structure and the chemical composition of the low-mass star- forming region NGC 1333 with spectral maps at 325-375 GHz made with JCMT/HARP and Herschel-HIFI spectra of the 626-800 GHz range (Band 2). In this study we focus on the 2 of the brightest deeply embedded Class 0 protostars called A and B in the NGC1333-IRAS 4 region, and we present the 2'×2' JCMT maps (Ө=15'') of DCO+, H2D+, + N2H+, HCO+ and H13CO . H2D+ shows an interesting spatial distribution that differs from that of the other ions. Furthermore, the analysis of the HIFI data reveals broad (H2O) and narrow emission along with some absorption features, which trace the different origin of the species (i.e. envelope, core). We also present some preliminary results of the excitation conditions in IRAS 4A region.

28 16. Uniformity of the mid-IR sky background for the size of E-ELT Mayuresh A. Kulkarni Leiden Observatory, Leiden University

For accurate background calibration of METIS, the mid-IR instrument on the E-ELT, it will be crucial to understand the spatial and temporal variations of the thermal emission of the atmosphere. We have analysed a series of short exposures taken simultaneously at the two VLT 8m telescopes. The study of the variations in the emission patterns will help us to understand whether the background in the mid-IR is spatially flat over 8 meter and ~50 meter scales on the sky. The data show some structures in the both pupils that move across the pupil with time. If atmospheric, the size of these structures would correspond to 1 to 4 meters on the sky. The estimated speed of these features would be a couple of magnitudes higher than the maximum wind speed at which the VLT can operate. It suggests that the dominant features are not located at an atmospheric layer near the telescope. This poster presents the characterization of the identified features, describes their possible origin and addresses the uniformity of the sky background in the mid-IR wavelengths.

17. Surface Formation of Water in Interstellar Ice Analogues Thanja Lamberts Leiden Observatory, Leiden University

A combination of observational, modeling and laboratory data has recently shown that a rich and complex molecular chemistry occurs in the Interstellar Medium. Gas-phase reactions cannot fully account for the observed complexity in space, therefore surface reactions on icy dust grains can provide an efficient complementary pathway. Water is the most abundant molecule in interstellar ices. Already in 1982 surface formation of water ice has been proposed to proceed through three hydrogenation channels: + O/O2/O3 H. This model was however only supported by gas-phase data available at that time. The work presented here combines (1) recent experiments of these reaction schemes in the solid phase with (2) Continuous Time Random Walk Monte Carlo simulations. The experiments have been performed in a ultra-high vacuum setup + where the O2 and O3 hydrogenation pathways were tested. The Monte Carlo simulations are here used as a tool to constrain the reaction barriers that will subsequently be implemented in future astrochemical models.

18. Flux recipes throughout the entire evolution of gamma-ray burst afterglows Konstantinos Leventis Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Gamma-ray burst afterglows are well described by synchrotron radiation originating from a decelerating, initially relativistic blast-wave. However, models used to interpret observations are often confined to particular dynamical phases, or spectral regimes. We present simulation-calibrated, analytic prescriptions for broadband synchrotron spectra applicable to a wide range of observer times that include the relativistic, trans- relativistic and Newtonian phases of a spherical outflow. Combined with a fitting algorithm these flux-prescriptions can provide an accurate and efficient way of extracting values of important physical parameters of gamma-ray bursts regardless of the dynamical phase of the afterglow.

29 19. Time dependent RT model of AGN dust tori Noel Lopez Gonzaga Leiden Observatory, Leiden University

To quantitatively understand AGN fueling and feedback we need to understand very basic facts like the form, size and dynamics of the dusty molecular gas reservoir. Stationary clumpy radiative transfer models have revealed more information about the structure of the tori. In order to understand more about the physics and behaviour of the dust tori we need to take in account efects such as variations in the luminosity of the central source, light travelling efects, etc. This is the reason why we are constructing a temporal radiative transfer model that can tell us more about the response of the tori against such changes. Results can be later compared with observations from MIDI (VLTI).

20. The transitional disk HD169142: measuring the gap size Koen Maaskant Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The disk around the Herbig Ae star HD169142 was imaged and resolved at 18.8 and 24.5 micron using Subaru/COMICS. We interpret the observations using a 2D radiative transfer model and find evidence for the presence of a large gap. The MIR images trace dust that emits at the onset of the strong rise in the spectral energy distribution (SED) at 20 micron therefore are very sensitive to the location and characteristics of the inner wall of the outer disk and its dust. We determine the location of the wall to be 23 AU from the star. An extra component of hot dust must exist close to the star. We find that a hydrostatic optically thick inner disk does not produce enough flux in the NIR and an optically thin geometrically thick component is our solution to fit the SED. Considering the recent findings of gaps and holes in a number of Herbig Ae/Be group I disks, we suggest that such disk structures may be common in group I sources. Classification as group I should be considered a support for classification as a transitional disk, improved imaging surveys are needed to support this speculation.

21. Rotational Velocities of the Single O-Stars in the VFTS Oscar Ramirez Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The VFTS-FLAMES TARANTULA SURVEY has obtained multi-epoch optical spectroscopy of over 300 “O” type stars in the 30 Doradus region of the Large Magallanic Cloud (LMC). As a first goal of my PhD program, I am mainly working on the quantitative spectroscopic analysis of the rotational velocity in the “O”; Single Sample of the VFTS by applying two different methods (Fourier Transform and Goodness of Fit). Therefore, for this poster, I am to discuss the methods and then the current results on the projected rotational velocity of our sample. Finally, a Vrsini distribution it's going to be presented.

30 22. The origins of the solar system: migration and dissolution of the Sun’s birth cluster Carmen Adriana Martinez Barbosa Leiden Observatory, Leiden University

A detailed study of the origin and life history of the sun and its birth cluster could serve to explain the history of earth's climate, the causes of mass extinctions and, in the field of astrophysics, how clusters migrate and are dissolved into the potential of the Milky Way. A better understanding of cluster migration and dissolution will enable us to answer several questions: Can the Milky Way disks be explained as having been built up from stars formed in clusters? How does cluster migration affect age and metallicity gradients in the disk? Can individual stars in moving groups be traced to their parent cluster? Can we do this for the sun and find its siblings? This project is focused on answering the last question. To do this, we will perform a set of cluster simulations in a very realistic Galactic potential which will include the contribution of spiral arms, the central bar and molecular clouds. Furthermore, the clusters will be simulated taking into account self gravity, stellar evolution and the effect of their birth clouds. These simulations will be done within the AMUSE (Astrophysical Multipurpose Software Environment) and the results will be combined with chemical tagging searches for solar siblings conducted at the Lund and Bordeaux observatories.

23. The Impact of Non-Equilibrium Ionisation on Gas Cooling in the ISM Alex Richings Leiden Observatory, Leiden University

We present a simple model to follow the chemical evolution of the most important coolants in the interstellar medium, including OI, CII, SiII and FeII. Due to the limited extent of the reaction network that we use in this model it is computationally fast enough to be included in numerical galaxy simulations. This enables us to evaluate the cooling rate of the ISM gas in such simulations without needing to assume ionisation equilibrium. We implement this model in the N-body/SPH code Gadget and use it to run simulations of an isolated dwarf galaxy at a high enough resolution to separate the warm and cold phases of the ISM. Using these simulations we investigate the impact of our chemical model on the cooling properties of the ISM gas.

24. Curious Sources in a LOFAR Deep Field Aleksandar Shulevski Kapteyn Astronomical Institute, University of Groningen

I have imaged a wide (25 degrees squared) field at 60 MHz using LOFAR with a bandwidth of 6 MHz and an observation time of 6 hours. The noise level reached in the image is around 25 mJy / beam, which is roughly 5 times the thermal noise at these frequencies. 130 sources were identified at a statistically significant detection level of 5 * r.m.s noise measured in the image. I present the properties of these detections as well as the discovery of previously unseen sources.

31 25. Hierarchical octtree grids in Monte Carlo radiative transfer simulations Waad Saftly Astronomical Observatory, University of Gent

The Monte Carlo method is the most powerful approach to perform radiative transfer simulations in a general 3D environment. An important aspect of any Monte Carlo simulation is the discretization of the dusty medium in tiny cells: ideal grids should contain as few cells as possible while still resolving the smallest structures that are important for the radiative transfer problem. We have implemented an advanced octtree-based grid structure in the 3D Monte Carlo radiative transfer code SKIRT. The method allows for either a regular or a barycentric iterative subdivision of the cells. As Monte Carlo simulations are based on billions of photon packages moving through the dusty medium, it is extremely important to make the calculation of individual paths as efficient as possible. We have implemented two new bottom-up methods for octtree traversal (neighbour search and bookkeeping), and compare them with a more straightforward top-down method. We find that these bottom-up algorithms are faster than the top-down algorithm, which allows large 3D Monte Carlo simulations to be executed.

26. Herschel-HIFI CO observations of protostars across the mass spectrum Irene San Jose Garcia Leiden Observatory, Leiden University

Stars form in molecular clouds and the chemical composition of protostellar material depends strongly on the physical conditions at the different evolutionary stages. In order to better constrain the physical structure of young stellar objects (YSOs) across 5 the entire mass spectrum (from < 1 to > 10 Lsun ), high-J (J < 11) CO and isotopologue transitions are observed with the Heterodyne Instrument for the Far Infrared (HIFI) on Herschel. CO is a well-known tracer of physical conditions in YSOs and provides a reference to determine the abundances of other species. For this reason, CO observations are fundamental in the key program “Water In Star-forming regions with Herschel” (WISH), and highly complementary to those of water. The main goal of this work is to provide a link from low- to high-mass YSOs by comparing the characteristics and properties of the CO emission line profiles. Similarities and differences in the spectra of different YSOs will be presented and various correlations investigated. Important results include the characterisation, by statistical analysis, of the two velocity components identified in the line profiles of 12CO (10-9) and 13CO (10-9), structures also detected in water lines by HIFI. In addition, a similar behaviour of the dynamics of the envelope (turbulence)-outflow system is found by studying the line widths of C18O (9-8) and 12CO (10-9) across the entire sample of YSOs. A strong correlation between the integrated intensity and the bolometric luminosity for all the CO and isotopologue emission lines is also obtained. Complementing the HIFI observations, spectral line maps from ground-based telescopes are compared with the high-J CO data in order to determine line ratios and constrain the kinetic temperature and column density in the different velocity components. The data will allow us to achieve a uniform description of the interaction of YSOs with their surroundings and to better characterize the star-formation process without mass boundaries.

32 27. Recent results from the Pierre Auger Observatory Johannes Schulz Astronomy Department, Radboud University Nijmegen

The Pierre Auger Observatory aims to gain further knowledge about the nature of Ultra High Energy Cosmic Rays (UHECR) with energies exceeding 1017 eV. The facility is leading the field of UHECR research by combining two prominent instrumentation methods. On one hand, a large array of water-Cherenkov detectors measures secondary particles, produced in the air shower cascade. On the other hand, telescopes detect fluorescence light emitted by nitrogen molecules, which are excited by the secondary particles in air showers. This allows a cross-calibration between the experimental methods and offers the unique opportunity to investigate the character of cosmic rays. The poster will present actual results from research performed by the Pierre Auger Collaboration. Emphasis is placed on recent findings about the energy spectrum, the mass composition, and the arrival direction of Ultra High Energy Cosmic Rays.

28. The connection between Dwarf Galaxies and Damped Lyman alpha systems Asa Skuladottir Kapteyn Astronomical Institute, University of Groningen

Dwarf galaxies are the most common type of galaxy in the present day Universe, where they are fairly evenly distributed through out every environment. The chemical properties of the oldest stellar populations in nearby dwarf galaxies offer a direct insight into the star formation processes at early times. From these properties it is possible to determine if metal enriched outflows from dwarf galaxies can have substantially enriched the Universe from very early times. Such galaxies thus become interesting comparisons to the abundance patterns seen in Damped Lyman alpha absorption systems at high redshift.

29. FRATS: Searching for Fast Radio Transients in real-time with LOFAR Sander ter Veen Astronomy Department, Radboud University Nijmegen

Stars, neutron stars, and planets can all emit pulses on timescales shorter than a second. Searching for these pulses gives us a chance to find more of these objects, to learn more about their emission mechanism, and has the potential to discover new classes of radiation mechanisms. In recent years these searches have led to the discovery of the Rotating Radio Transients (RRATS), that only emit occasionally, and the discovery of the Lorimer Burst, whose astrophysical origin is still under debate. In this contribution I will explain that the LOFAR radio telescope has excellent capabilities to search for these pulses in real-time, while other observations are also done, how we can use the LOFAR time-machine to determine the origin of the pulse, without the need of follow-up, and show first results of our efforts.

33 30. Interactions between dwarf galaxies and dark satellites Tjitske Starkenburg Kapteyn Astronomical Institute, University of Groningen

Within the LCDM cosmogony small dark matter halos are predicted to be very abundant. A large majority of these small haloes however, will never get massive enough to form stars and lighten up and will therefore remain ‘dark’, but may leave dynamical imprints in luminous galaxies. This motivates our poster on a suite of controlled simulations of dwarf galaxies and dark satellites. We simulate mergers between a dark satellite and a disky dwarf galaxy both with and without gas. The collisionless mergers show that dark satellites do perturb the disky dwarf, leading to significant thickening and important morphological changes. This thickening depends strongly on the mass ratios of the satellite to the host disk, which leads us to conclude that such encounters are likely to be important in the evolution of dwarf galaxies. Our simulations with gas show that the accretion of a dark satellite can induce a starburst. The increase in the star formation rate ranges from a few to factors greater than ten, depending on the orbital characteristics of the encounter. Interestingly, in such cases the dominant starburst is located in the center of the (eventually) accreted dark satellite, thereby lightening it for a brief period of time after which it finally merges with the dwarf.

31. The Galactic Halo in the Gaia era Pim van Oirschot Astronomy Department, Radboud University Nijmegen

The Galactic Halo is the oldest and most metal-poor component of the Galaxy. It is studied in detail both to understand the formation and evolution of galaxies, as well as the formation and evolution of the earliest stars. We simulate the properties of the population of white dwarfs in the halo of our Milky Way galaxy, making different assumptions about the initial mass function and the star formation history. These simulations can be compared with the results of the Gaia satellite, which is on schedule to be launched in June 2013.

32. Long period subdwarf binaries as tracers for binary stellar evolution Joris Vos Institute of Astronomy, Katholieke Universiteit Leuven

Subdwarf B stars (sdBs) are core-helium burning stars with very thin hydrogen envelopes. They are situated between the main sequence and the white dwarf cooling track at the blueward extension of the horizontal branch, the so-called extreme horizontal branch. Currently there are five evolutionary channels that are thought to produce sdB binaries, all of which involve complex binary interaction processes. They predict that the majority of sdBs should form through stable mass transfer leading to long-period binaries. Although many short-period systems are known, only very few long-period sdB binaries have been studied. As part of a long term observing program to map the orbital periods of sdB binaries we describe the first post-Roche-lobe- overflow long-period systems using a combination of high-resolution spectra obtained with HERMES at the Mercator telescope, and multi-wavelength photometric measurements.

34 33. The Moon as a neutrino telescope Stijn Buitink KVI – University of Groningen

Cosmic neutrinos are important messenger particles that can provide us with information about the highest energy sources in the universe. They travel unattenuated, in straight lines, over great distances, but are notoriously hard to measure. Optical Cherenkov neutrino telescopes, such as IceCube and Antares, search the sky for TeV and PeV neutrinos from many sources, including gamma ray bursts, supernova remnants and annihilating dark matter. At higher energies, there is an additional source of neutrinos. Above the GZK energy of 6.1019 eV, cosmic rays interact with the cosmic microwave background creating pions that decay into neutrinos. Measuring these ultra-high-energy neutrinos could reveal the nature of the most energetic accelerators in the universe. Such measurements require enormous detector volumes and novel detection techniques. Using LOFAR, we aim to turn the whole visible lunar surface into a neutrino detector. When ultra-high-energy particles hit the lunar soil, they initiate a particle cascade that will emit radio emission through the Askaryan mechanism. These ultra-short radio flashes can escape the Moon and travel towards the Earth, where they can be recorded by sensitive radio telescopes. An earlier search for lunar radio flashes with the Westerbork Synthesis Radio Telescope resulted in today's most stringent limit on cosmic neutrinos at the highest energies (>1022 eV). LOFAR, and later SKA, will reach even better sensitivities and push down the energy thresholds, which could lead to an important breakthrough in astroparticle physics.

34. The GAIA Photometric Data Processing Giorgia Busso Leiden Observatory, Leiden University

This is an overview of the processing of the dispersed images for the Blue and Red Photometers (BP, RP) in the Gaia Satellite. The data are corrected for CCD related effects in the pre-processing, where also the sky background and the flux by neighbors are removed; the data are then internally calibrated to the same ”mean instrument” and externally calibrated to obtain spectrum and flux in physical units, which will be stored in the final catalogue.

35. Hershel's stunning view of the disk around Fomalhaut Michiel Min Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The Hershel space telescope has provided beautiful images of the dust disk surrounding Fomalhaut. Since the star is weak at the long wavelengths of the images we can clearly resolve the surrounding dust and constrain its properties. Doing this we derive constraints on the dynamics of the ring, and the characteristics of the dust particles.

35 36. Locating the fast HI outflows in radio galaxies Elizabeth Mahony ASTRON Netherlands Institute for Radio Astronomy

It is widely recognised that the evolution of galaxies and their central black holes are strongly linked. In recent years, this has been attributed to feedback mechanisms where the interplay between the radio jets and surrounding medium is believed to play an important role in the evolution and life cycle of active galaxies. To investigate this, we have obtained EVLA observations of 3 radio galaxies: 3C293, 3C236 and 3C459 to search for fast outflows of neutral gas. Pinpointing the location of these outflows (i.e. if they occur close to the central core or are associated with the radio jets or hotspots) will enable us to derive crucial parameters such as the mass outflow rates and kinetic energy involved, resulting in a greater understanding of feedback processes in galaxy evolution.

37. VLBI and Doppler tracking of Venus Express spacecraft Guifré Molera Calvés JIVE Joint Institute for VLBI in Europe

Very Long Baseline Interferometry (VLBI) and Doppler tracking is one of the most powerful tools for determining accurately the position of a planetary spacecraft. The Planetary Radio Interferometry and Doppler Experiment (PRIDE), an initiative by the Joint Institute for VLBI in Europe, is a multi-purpose, multi-disciplinary enhancement of planetary missions science return. PRIDE is able to provide ultra precise estimates of spacecraft state vectors based on the VLBI phase-reference and radial Doppler measurements. As a preparatory stage for the future deep space missions, PRIDE has been conducting test observations with several ESA’s planetary spacecraft for the last three years (2009-2012). The ESA Venus Express (VEX), launched in 2004, has been the primarily target of our single-dish and VLBI observations. The VEX single-dish observations have been crutial to determine the characteristic of the interplanetary scintillations (IPS) at different solar elongation and at various distances to the target. The analysis of the phase fluctuations on the spacecraft signal allows us to determine the best time frame for the approach, descent and landing operations for spacecraft to achieve precise estimation of the state vectors with VLBI spacecraft tracking.

38. New results of the hi-res survey of Galactic HI halo clouds Yurii Pidopryhora JIVE Joint Institute for VLBI in Europe

In 2003-2007 a number of selected dense Galactic HI halo clouds were observed with the VLA in D, C and B arrays, with the GBT to provide the short-spacing flux. The measurement of physical properties of these clouds allows to derive a general picture of conditions in the Galactic halo ISM. New results of this survey will be presented.

36 39. Attitude Considerations Regarding the Astrometry of Gaia Daniel Risquez Leiden Observatory, Leiden University

The main goal of the Gaia mission is to obtain extremely accurate astrometry, and this astrometry is measured with respect to the attitude of the spacecraft. Therefore perturbations in the attitude would degrade the astrometrical output of the mission. Here we present an analysis of these perturbations and the expected error in the astrometry due to the attitude.

40. Gaia: one year before launch Anthony Brown Leiden Observatory, Leiden University The Gaia mission is about on year away from its planned launch in August 2013 and it is time for the astronomical community to start preparing in earnest for the scientific analysis of Gaia's results. I will discuss the status of the Gaia mission, which is scheduled present the anticipated scientific performance. I will also present the proposal for the early data releases from the Gaia mission and the ideas for making the Gaia results accessible through advanced data access facilities. Finally I present the simulated Gaia catalogues that are available for preparing the scientific exploitation of the results.

41. PyCRTools: A software toolset for analyzing cosmic-ray signals in radio observations Martin van den Akker Astronomy Department, Radboud University Nijmegen

In this contribution we present the PyCRTools software library: a toolset for processing radio observations, like from LOFAR, for the analysis of VHECR (very-high energy cosmic rays). It provides a framework for creating data analysis pipelines for large datasets with both rapid development and fast and efficient processing as its main keypoints.

42. Twittering at warp speed Franka Buurmeijer Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Don't you feel privileged? Aren't you glad you may discover more about our universe every day? Then share this with the world! You can do this simple and quick through twitter. This poster will explain the benefits that twittering by astronomers may have to the society, to astronomy in general and to a single astronomer. Some basic rules of twitter are explained by which the beneficial effects are optimized. Enough information for a start on twitter at warp speed!

37 43. Atomic gas, molecular gas and dust in HEROES edge-on spiral galaxies Flor Allaert Astronomical Observatory, University of Gent

HEROES (HERschel Observations of Edge-On spirals) is a project aimed at understanding the distribution and properties of interstellar dust, and its connection to the gas and stellar components, in seven nearby, large edge-on spiral galaxies. The edge-on geometry of these galaxies makes it possible to constrain their dust content based on not only the thermal dust emission in the FIR/submm, but also the dust extinction in the optical. In this poster presentation, we present deep HI interferometric 21 cm observations of the 7 HEROES galaxies, based on archival VLA, ATCA and WSRT data and new GMRT data. From these data, the 2D morphology, radial surface density profiles and rotation curves of the atomic gas were derived using techniques suited for an edge-on geometry. From the rotation curves, dynamical models of the galaxies are being derived. We also present preliminary results of new CO(1-0) observations of one of the galaxies, recently conducted at the Nobeyama 45-m telescope (Japan). The radial distribution of the atomic and molecular gas is compared to that of the dust to determine the radial variation of the gas-to-dust ratio.

44. Thermal compaction of porous interstellar ices Martin de Valois Leiden Observatory, Leiden University

A detailed laboratory study has been performed in which the compaction rate is determined for porous amorphous solid water (ASW), compact ASW and crystalline solid water – quantitatively - upon heating in an astronomically relevant temperature regime (20-120 K). For this a new technique has been developed that combines optical interference and Fourier transform infrared spectroscopy and that allows determining the loss of porosity in situ and in real time. Porous ASW is found to undergo a compaction of 10 +/- 0.5 % upon heating. The compaction of compact ASW is less and negligible for crystalline solid water. This is consistent with the non-detection of porous ASW in the interstellar medium. The increased compaction has consequences for the catalytic properties of the ice that are discussed.

45. Ballistic study of Herbig Haro-jets Jacqueline den Hartogh Astronomical Institute 'Anton Pannekoek', University of Amsterdam

YSO jets or Hebig Haro (HH) objects are collimated outflows which are detected through characteristic emission lines. They are found in star-forming regions and are recognized as manifestations of the accretion activity of newborn stars. Recently HH objects HH1042 and HH1043 were discovered and observed with X-shooter, a spectrograph on the ESO Very Large Telescope. The acquired spectra enable us, for the first time, to study the jet diagnostics in both the optical and near-infrared wavelength domain. The simplified, ballistic jet-model of Raga et al (1990), also applied by Ellerbroek et al (in prep), will be the starting point for studying the kinematics of the two HH objects. The next step will be to construct a more physical model that predicts the evolution of the jets. In addition to this, MHD codes like Pluto or AMR-VAC, can be used.

38 46. VLT/X-Shooter spectroscopy of the very massive binary WR 21a Nicola Fitzsimons Astronomical Institute 'Anton Pannekoek', University of Amsterdam

The Wolf-Rayet (WR) star WR 21a, located in the Large Magellanic Cloud, is believed to be one of the most massive binary systems. Evidence to support this comes from a previously published orbital solution resulting in minimum stellar masses of 87 and 53M⊙ . Other evidence has been shown in X-ray emission which is considered to be the result of a colliding wind interaction. The optical spectrum indicates that the companion is most likely an O-type star but firm identification has not yet been achieved. To investigate the binary properties we have obtained multi-epoch VLT/X- shooter observations of WR 21a. The resulting spectra allow the study of radial velocity variations, and a disentanglement of the emission lines (of the WR) and absorption lines (for the companion) over a wavelength range from near- UV to the near-IR. Furthermore, this may allow for a quantitative spectral analysis of both components. Subsequently we will aim to produce the most comprehensive analysis of this system to date. On this poster we present an overview of the project and the first results of our analysis.

47. Evolution of hierarchical triple systems Adrian Hamers Utrecht University

Hierarchical triple systems are three-body systems which are dynamically stable over long timescales. They are well-described in terms of two perturbed Keplerian orbits, those of the inner and outer binary systems. A most notable perturbation is the periodic change of the inner orbit eccentricity on a timescale of typically a few Myr, potentially reaching very high values close to unity. These cycles of eccentricity (also known as Kozai cycles) have significant influence on the evolution of stellar hierarchical triple systems, in particular in the inner binary system. In the latter system, high eccentricities may induce episodes of strong tidal friction, or, in the more extreme cases, orbital collision of the two components. To investigate the possibilities when taking into account the dynamical gravitational influence of a tertiary in a stable orbit around a binary system, we have extended an existing binary population synthesis code with a module which takes into account the effects of the tertiary. We find a variety of new “triple”; evolution channels, among which a channel in which a double degenerate supernova type Ia (SNIa) occurs in binary systems which are non- interacting in the absence of a tertiary. The latter channel may provide a means of (partly) solving the outstanding discrepancy between the predicted rate of SNIa in (binary) population synthesis studies and the observed rate.

39 48. Transit timing variations of the hot Jupiters WASP-43b and WASP-46b and the super Earth GJ-1214b Mathias Polfliet Astronomical Observatory, University of Gent

Transit timing analysis is proving to be an efficient method to detect planetary partners in systems which already have transiting planets present, particularly in the orbital resonances of the system. In these resonances we might be able to detect Earth- mass objects well below the current detection and even theoretical ( due to stellar variability ) thresholds of radial velocity. We present four new transits for WASP-46b, four new transits for WASP-43b and seven new transits for GJ-1214b using the TRAPPIST telescope located at the ESO La Silla Observatory. Observations were made in a special 'I+z' and a Johnson-Cousins Ic filter. Modelling the data was done using several Markov Chain Monte Carlo (MCMC) simulations. We investigated given systems for Transit Timing Variations (TTVs) and variations in the other transit parameters and found no significant (3σ) deviations. Based on the RMS of the TTVs we designed a tool using the MERCURY package by Chambers to exclude possible planetary partners.

49. HeidelSat - A CubeSat to Measure the Flux of Cosmic-Ray Particles Jeroen van Asten Astronomy Department, Radboud University Nijmegen

The Earth is permanently exposed to ionized atomic nuclei impinging on the atmosphere from outer space - the cosmic rays. CubeSats are the standard for picosatellite design with a nominal length of 100 mm per side and not exceeding 1.33 kg mass. CubeSats provide an interesting platform to measure the flux of cosmic rays outside the atmosphere of the Earth. We are developing a low-power cosmic-ray detector to be installed in a CubeSat. The detector comprises a plastic scintillation counter, read out by an avalanche photo diode. The measured counting rate of cosmic- ray particles is transmitted to a ground station. The plans will be outlined and the current status of the project, including test results will be presented.

50. FRIEDL: dust in early-type galaxies Sébastien Viaene Astronomical Observatory, University of Gent

The geometry, origin, heating mechanism and optical properties of dust in early-type galaxies is not well understood. In the frame of the Far-infraRed Investigation of Early- type galaxies with Dust Lanes (FRIEDL) project, we have selected a sample of 11 early- type galaxies with prominent dust lanes. Here, we present an analysis of the five northern galaxies of the FRIEDL sample. These galaxies have been observed at far- infrared wavelengths with the Herschel Space Observatory, and at optical/near- infrared wavelengths using the San Pedro Mártir and Himalayan Chandra Telescope. We construct color maps and attenuation maps at optical and near-infrared wavelengths and use these maps to derive spatially resolved dust maps and total dust masses. These optical dust masses are compared to dust mass estimates based on IRAS, Akari and Herschel far-infrared data.

40 51. Dust in bow shocks and shells: Probing the interaction between stellar winds and the ISM Nick Cox Institute of Astronomy, Katholieke Universiteit Leuven

In this contribution we present recent results of Herschel/PACS far-infrared imaging of AGB stars, red supergiants and runaway OB stars. We focus on spatially resolved bow shocks and detached shells. Previously only a handful of stellar wind bow shocks were known for evolved objects, but we now find them around 80% of nearby AGB stars. For young massive stars the typical sizes of bow shocks are larger and the dust appears hotter and thus these have been more readily detected in the past. The ubiquitous occurrence of bow shocks around evolved stars could have a decisive effect on the ultimate composition and properties of the material expelled by (evolved) stars and mixed into the ISM. Here we present a range of far-infrared (dust) emission morphologies that arise when the stellar wind interacts with the surrounding medium leading to a pile-up of matter in the wind-ISM interaction zone, giving rise to a bow shock. From theoretical predictions as well as hydrodynamical simulations we see that the shape and size of these interaction regions is set by a delicate balance of stellar (mass-loss, velocity) and interstellar (density, temperature) properties. We find clues which suggest that both binarity as well as internal stellar processes can be decisive in the shaping of the observed interaction regions. Also, the presence of turbulent instabilities predicted by simulations is observed for some objects. In addition to the general survey results we will highlight a few notable individual objects, such as CW Leo, Betelgeuse and Zeta Oph, for which we have complementary data as well.

52. VLBI and Doppler tracking of Spacecraft Dmitry Duev JIVE Joint Institute for VLBI in Europe

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is designed as a multi-disciplinary enhancement of a planetary mission science return by means of precise estimates of the spacecraft state vectors. These estimates can be used for a variety of applications starting from studies of planetary bodies gravitational fields and their interior all the way to gravitational physics experiments. During the last two years, as a preparatory stage for PRIDE, several operational planetary spacecraft have been observed with the European VLBI radio telescopes. The PRIDE group has been developing a suite of software tools for measurements of the Doppler-shift of the spacecraft carrier signal and accurate estimates of the spacecraft state vectors using the VLBI phase referencing technique. In this talk, the latest results of PRIDE observations of the ESA Venus Exspress (VEX) spacecraft and the Russian space VLBI mission RadioAstron with the European VLBI Network (EVN) radio telescopes are presented. In these experiments, a milli-Hz level of the radio signal spectral resolution and extracted the phase of the spacecraft carrier signal with the accuracy of 0.1 radian have been achieved. The data processing, reduction and analysis pipeline, which allows a highly accurate determination of spacecraft state vectors, will be explained in the talk.

41 53. The radial velocity trail of the giant planet Tau Boötis b Matteo Brogi Leiden Observatory, Leiden University

The giant planet orbiting Tau Boötis was among the first extrasolar planets to be discovered through the reflex motion of its host star. It is one of the brightest known and most nearby planets with an orbital period of just a few days. Over the course of more than a decade, measurements of its orbital inclination have been announced and refuted, and have subsequently remained elusive until we recently detected carbon monoxide absorption in the thermal day-side spectrum of Tau Boötis b. At a spectral resolution of R~100,000, we trace the change in the radial velocity of the planet over a large range in phase, determining an orbital inclination of i=44.5±1.5 degrees and a true planet mass of 5.95±0.28 Jupiter masses. The strong absorption signal points to an atmosphere with a temperature that is decreasing towards higher altitudes. This is a stark contrast to the temperature inversion invoked for other highly irradiated planets, and supports models in which the absorbing compounds believed to cause such atmospheric inversions are destroyed by the ultraviolet emission from the active host star. This result finally extends atmospheric characterisation to non-transiting planets, by far the majority of the known sample of exoplanets.

54. Scaling relations of simulated galaxies from the EAGLE simulation Peter Camps Astronomical Observatory, University of Gent

The EAGLE simulation is a forthcoming cosmological hydrodynamical simulation that will use more than 10 billion particles. The simulation code will include detailed recipes for star formation, gas cooling, stellar evolution, and feedback from supernovae and AGN. The simulation itself will be the largest ever performed, allowing for the first time to numerically resolve thousands of galaxies in a representative cosmological volume that also contains groups and clusters. We present preliminary results of 3D non-LTE dust radiative transfer simulations aimed at calculating the observable properties from UV to mm wavelengths of simulated galaxies from EAGLE test simulations. We discuss the main challenges encountered and the appropriate techniques applied to overcome these challenges. We present scaling relations of the simulated galaxies and compare them with the observed scaling relations from the GAMA survey.

55. Detection of cosmic filaments and walls Marius Cautun Kapteyn Astronomical Institute, University of Groningen

The large scale distribution of dark matter, galaxies and gas does not follow a random pattern, but traces a wispy weblike arrangement of dense compact clusters, elongated filaments and sheetlike walls, amidst large near-empty void regions. During my talk I will present a novel approach for the detection of this Cosmic Web. The success of this method lies in its multiscale and user-independent character which facilitate in resolving the hierarchical nature of the large scale structures. Towards the end of my talk I will touch on the application of this method in a better understanding of the connection between cosmic environments and galaxy properties and evolution.

42 56. Post-AGB stars as tracers of chemical evolution: the extreme s-process enriched post-AGB star J004441.04-732136.4 Kenneth de Smedt Institute of Astronomy, Katholieke Universiteit Leuven

This talk is based upon the accepted A&A paper: 'Post-AGB stars in the SMC as tracers of stellar evolution: the extreme s-process enrichment of the 21 micrometer star J004441.04-732136.4'. We focus on the still poorly understood Asymptotic Giant Branch (AGB) third dredge-up processes and associated s-process nucleosynthesis. Synthesis by the s-process in AGB stars is an important contributor to the cosmic abundances past the iron peak and these stars are also thought to be very important contributors to the total carbon and nitrogen enrichment in the Universe. However, because of multiple reasons, accurate determination of photospheric abundances in AGB stars is difficult. The subsequent stellar evolutionary stage does not have these problems making post-AGB stars ideal probes of the AGB nucleosynthesis and third dredge-up. Because of the well constrained distance with respect to Galactic post-AGB stars, we confront accurate spectral abundance analyses of post-AGB stars in both the Magellanic Clouds to state-of-the-art AGB model predictions. With this comparison we aim at improving our understanding of the 3rd dredge-up phenomena and their dependencies on initial mass and metallicity. In this talk, we focus on the only known 21 micrometer object in the Small Magellanic Cloud (SMC): J004441.04-732136.4. An accurate spectral abundance analysis reveals this object to be one of the most s- process enriched objects up to date with very strong s-element overabundances but with a low C/O ratio which is unexpected. With photometric data of multiple catalogues, we construct a spectral energy distribution and perform a variability analysis of this object. The abundance results are then compared to predictions of tailored theoretical chemical AGB evolutionary models for which we used two evolution codes. We show that our theoretical predictions match the s-process distribution, but fail in reproducing the detected high overabundances and predict a high Pb abundance which is not detected. Additionally, there remain serious problems in explaining the observed pulsational properties of this source. With these and future results, we hope to improve theoretical AGB models.

57. Evolution of the EW(Hα) and its dependence on stellar mass, from z=0 to z=2.2 Mattia Fumagalli Leiden Observatory, Leiden University

We investigate the evolution of the Hα emission in redshift and its dependence on stellar mass, taking advantage of the first data from the 3D-HST survey (Brammer et al, in prep.), a large (248 orbits) slitless spectroscopic program with HST-WFC3. Combining our Hα measurements of 854 galaxies at 0.8 < z <1.5 with those of ground based surveys at lower redshift, we can now measure the evolution consistently from z=0 to z=2.2. We find that at each redshift EW(Hα) is lower for high-mass galaxies and that at a fixed mass bin EW(Hα) increases with redshift, with no mass dependence in the slope of EW(Hα) ~ (1+z)1.87. This measure is a completely independent confirmation of the evolution of star forming galaxies in redshift. The sSFR evolves faster, as the mass-to-light ratio also evolves with redshift. We find that the sSFR evolves like ~ (1+z)3.17, nearly independent with mass. We show that a simple argument based on halo-accretion and density matching gives a value of (1+z)3.3, close to the observed.

43 58. FitSKIRT, genetic algorithms applied to automatically fit with a radiative transfer code Gert de Geyter Astronomical Observatory, University of Gent

We present FitSKIRT, a code to fit radiative transfer models to optical/near-infrared images of dusty galaxies. The goal of this code is recover the 3D distribution and spectral properties of dust and stars from a set of observed images. FitSKIRT combines the general 3D Monte Carlo radiative transfer code SKIRT with an optimization library based on genetic algorithms. The final result is a fully automatized fitting procedure that uses the least amount of human intervention and thus effectively eliminates any form of biasing. The method can be used to fit either monochromatically or use one input model to fit a set of observations ranging from UV to near-infrared bands. We show the accuracy and power of FitSKIRT by applying it on a number of artificial and real images of dusty galaxies. We present the results of panchromatic modeling of a number of large edge-on spiral galaxies selected from the HEROES program. We also present preliminary results of radiative transfer modeling of dust-lane early-type galaxies and face-on spiral galaxies.

59. The Effect of Angular Opening on the Dynamics of Relativistic Hydro Jets Context Rémi Monceau-Baroux CPA laboratory - Katholieke universiteit Leuven

Relativistic jets emerging from AGN cores transfer energy from the jets to their surrounding interstellar/intergalactic medium through shock- and instability mediated hydrodynamic mechanisms. As jets are observed to have finite opening angles, one needs to quantify the role of conical versus cylindrical jet propagation in this energy transfer. Aims. We adopt parameters representative for FR-II AGN jets with finite opening angles, and show that such cases recollimate with a clear influence of the ISM/IGM density profile. We study how such an opening angle affects the overall dynamics of the jet and its interaction with its surrounding medium. Methods. This study exploits our parallel adaptive mesh refinement code MPI-AMRVAC with its special relativistic hydrodynamic model, incorporating an equation of state with varying effective polytropic index. We study initially mildly underdense jets up to opening angles of 10 degrees, at Lorentz factors of about 10, inspired by input parameters derived from observations. Instantaneous quantifications of the various ISM volumes affected by jet injection and their energy content allows to quantify the role of mixing versus shock-heated cocoon regions over the simulated time intervals. Results. We show that a wider opening angle jet results in a faster deceleration of the jet and leads to a wider radial expansion zone dominated by Kelvin-Helmholtz and Rayleigh-Taylor instabilities. The energy transfer mainly occurs in the shocked ISM region by both the frontal bow shock and cocoon-traversing shock waves, in a roughly 3 to 1 ratio to the energy mixing zone, for a 5 degree opening angle jet. The formation of nodes along the jet relates to X-ray emission blobs known from observations. A rarefaction wave induces a dynamically formed layered structure of the jet beam. Conclusions. Finite opening angle jets can efficiently transfer significant fractions (25 % up to 70 %) of their injected energy over a growing region of shocked ISM matter. The role of the ISM stratification is prominent in determining the overall volume affected by relativistic jet injection.

44 60. Comparing the CODEX models to PTI time series of TU And Michel Hillen Institute of Astronomy, Katholieke Universiteit Leuven

In this contribution, I will present the results of our comparison of near-IR interferometric time series of the Mira variable TU And to the CODEX dynamic atmosphere models. The public release of these models, allows the community to observationally test their validity. Although our results are inconclusive on the latter, they clearly demonstrate the need for a better coverage in the model parameter grid as current combinations of mass, metallicity, luminosity, mixing length parameter and turbulent viscosity parameter result in models that are not compatible with observations at visual maximum phases of the pulsation cycle. Our observations will definitely lead to a better theoretical understanding of evolved low-mass stars, which is important as these stars constitute one of the major sources of uncertainty in the modeling of (extra-)galactic stellar populations in the near to mid-IR. With the upcoming instrumentation on JWST and E-ELT, the latter will become increasingly paramount.

61. Dynamics of Starbursting Dwarf Galaxies Federico Lelli Kapteyn Astronomical Institute, University of Groningen

The mechanisms that trigger, sustain and quench starburst activity in galaxies are poorly understood. Blue Compact Dwarfs (BCDs) are nearby starbursting dwarf galaxies that may hold the key to understand these mechanisms. BCDs are characterized by two striking HI properties: i) strong concentrations of HI within the starburst regions, and ii) steep central velocity gradients. Both properties are not observed in more quiescent dwarfs. We are studying a sample of 18 BCDs and in several cases we are finding that the steep velocity gradient is due to a steeply-rising rotation curve that flattens in the outer parts. This points to a strong central concentration of mass. We decompose the rotation curves into mass components and find that baryons (stars and gas) are dynamically important. These are striking differences with respect to typical dwarf irregulars, which usually have slowly-rising rotation curves and are thought to be entirely dominated by dark matter. We discuss the implications of these results on the evolution of dwarf galaxies and in particular on the properties of the progenitors and descendants of BCDs. We also discuss interactions/mergers or cold gas accretion as likely explanations for the triggering of the starburst.

62. Is the HI in galaxies opaque? Stephan Peters Kapteyn Astronomical Institute, University of Groningen

In almost every analysis of the HI content of galaxies, there is an almost implicit assumption that the HI is optically thin. Thus, every part of the gas can and will be seen and a mass model of the galaxy can easily be derived. We believe that self-absorption of the neutral gas is far more important than suspected. The cold neutral medium could harbor far more gas than assumed. In this poster we list arguments in favor of this view. We also present our ongoing attempts to quantifying this hidden component.

45 63. The Evolution of Mass-size Relation for Lyman Break Galaxies from z=1 to z=7 Moein Mosleh Leiden Observatory, Leiden University

For the first time, we study the evolution of the stellar mass-size relation for star- forming galaxies from z ~ 4 to z ~ 7 from Hubble-WFC3/IR camera observations of the HUDF and Early Release Science (ERS) field. The sizes are measured by determining the best fit model to the galaxies images in the rest-frame 2100 Å and stellar masses estimated from SED fitting to rest-frame optical (using Spitzer/IRAC) and UV fluxes. We show that the stellar mass-size relation of Lyman-break galaxies (LBGs) persists, at least to z ~ 6, and the median size of LBGs at a given stellar mass increases towards lower redshifts. For galaxies with stellar masses of 9.5 < log(Mstar/Msun) < 10.4 sizes

-1.20±0.11 evolve as (1+z) . For galaxies with stellar masses of 8.6 < log(Mstar/Msun) ~ 9.5

-1.18±0.1 this evolution is re ∝o (1+z) ) . Our results are consistent with previous measurements of the LBGs mass-size relation at lower redshifts z ~ 1-3.

64. AERA - Detecting radio emission of cosmic ray air showers at the Pierre Auger Observatory Anna Nelles Astronomy Department, Radboud University Nijmegen

The Auger Engineering Radio Array (AERA) has been deployed within the Pierre Auger Observatory in Argentina to observe radio emission from extensive air showers. The Pierre Auger Observatory is currently the largest detector for cosmic rays at the highest energies. The colocation of AERA with the low-energy extensions of the Pierre Auger Observatory will enable us to test and further develop the new detection techniques as an independent detector for cosmic rays. This set-up will give the opportunity to learn more about the emissions mechanisms of the radiation. Furthermore, using the data from the existing observatory it will be explored in how far radio emissions are suitable tools for composition measurements of cosmic rays. The composition is still under debate at the highest energies and crucial to distinguish astrophysical models of the origin of cosmic rays. The set-up has been running stably for over a year now and has successfully detected cosmic rays. This is the first large- scale radio detection without relying on a trigger from traditional particle detectors. This talk will present the current status and recent results of the experiment will be discussed.

46 65. Properties of the inter stellar medium during the star-formation activity peak of the Universe Gergö Popping Kapteyn Astronomical Institute, University of Groningen

At redshift z~1-3 the star-formation activity of the Universe reached its peak, after which it dropped towards its current day value. In the near future ALMA will allow us to observe atoms and molecules like carbon, CO and HCN for large groups of star- forming galaxies during this cosmic epoch. Such elements are good tracers of the properties of the inter stellar medium (ISM) of these galaxies and can possibly give understanding to why the star-formation activity of the Universe decreased at lower redshifts. I will present our predictions for such observations, based on a semi-analytic galaxy formation model, combined with a radiative-transfer and line-tracing code. Our model is very successful in reproducing observations like the CO(1-0) luminosity vs. star-formation rate relation at z = 1-2, presented in Genzel et al. (2010). I discuss how the carbon content and the CO and HCN line ratios change with galaxy properties and redshift, and how this translates into changes in ISM properties of star-forming galaxies at these epochs. I will finish by laying out a strategy to test these predictions with ALMA.

66. First science results from SOFIA/FORCAST: The mid-infrared view of the compact HII region W3A Francisco Salgado Leiden Observatory, Leiden University

The massive star forming region W3 was observed with FORCAST on board of SOFIA as part of the Short Science program. The 6.4, 6.6, 7.7, 19.7, 24.2, 31.5 and 37.1 micron filters were used to observe the emission of PAH molecules, Very Small Grains and Big Grains. Optical depth and color temperature maps of W3A show that IRS2 has blown a bubble devoid of gas and dust of 0.05 pc radius. It is embedded in a dusty shell of ionized gas that contributes 40% of the total 24 micron emission of W3A. This dust component is mostly heated by far ultraviolet, rather than trapped Ly alpha photons. This shell is itself surrounded by a thin PDR where PAHs show intense emission. The infrared SED of three different zones located at 8, 20 and 25 from IRS2, show that the peak of the SED shifts towards longer wavelengths, when moving away from the star. Adopting the stellar radiation field for these three positions, DUSTEM model fits to these SEDs yield a dust-to-gas mass ratio in the ionized gas similar to that in the diffuse ISM. However, the ratio of the IR-to-UV opacity of the dust in the ionized shell is increased by a factor of 3 compared to the diffuse ISM.

47 67. Measuring cosmic rays with LOFAR Pim Schellart Astronomy Department, Radboud University Nijmegen

LOFAR is the largest radio telescope in the world for observing low frequency radio emission from 10 to 240 MHz. In addition to its use as an interferometric array, LOFAR is now routinely used to detect cosmic rays. These charged particles impinge upon the atmosphere with energies of up to the 10^20 eV. They develop an extensive air shower of secondary particles in the atmosphere which in turn interacts with the Earths magnetic field to produce low frequency radio emission. Using the collecting area and high antenna density of the LOFAR core we will for the first time be able to fully understand the yet unknown emission mechanism. Coupled with theoretical models this will allow us to directly measure the nature of the primary particle. I will present the progress that has been made by the LOFAR Cosmic Rays Key Science Project in detecting and understanding these particles.

68. The ACS Fornax Cluster Survey: The Nuclei of Early-Type Galaxies in the Fornax Cluster Monica Turner Leiden Observatory, Leiden University

The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both 1D and 2D techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central “luminosity excesses” relative to a Sérsic model fitted to the underlying galaxy. We find 72±13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 0.5" from the host galaxy photocenter. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters, and to follow different structural scaling relations. The nuclei colors are characteristic of intermediate to old stellar populations, with the majority of nuclei found to be bluer than their host galaxies. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We conclude that, for low-mass galaxies, the most important mechanism for nucleus growth is probably infall of star clusters through dynamical friction, while for higher mass galaxies, gas accretion triggered by mergers, accretions and tidal torques is likely to dominate, with the relative importance of these two processes varying smoothly as a function of galaxy mass. Some intermediate-mass galaxies in our sample show a complexity in their inner structure that may be the signature of “hybrid nuclei” that arose through parallel formation channels.

48 69. Radio galaxies of the local universe: a new all-sky catalog to study ultra-high energy cosmic rays and jet feedback Sjoert van Velzen Astronomy Department, Radboud University Nijmegen

The final episode in the history of black hole accretion and galaxy formation takes place in our cosmic backyard, the local universe. Low-redshift radio galaxies can thus be used to test theories of black hole growth and feedback. Moreover, the sources ultra-high energy cosmic rays observed on Earth are until now unknown yet must reside within 100 Mpc from us. A thorough study of the local volume requires full-sky coverage to obtain a sizable sample and map the matter anisotropy. However, none of the modern catalogs of active black holes cover the entire sky. We have matched the 2MASS Redshift Survey to Northern and Southern radio surveys to obtain an all-sky inventory of local radio galaxies. The sample contains all galaxies with an optical and radio luminosity as bright as Cen A out to 100 Mpc. Roughly 30% of the radio-emitting galaxies have hitherto not been cataloged as such. The powerful radio jets in our sample reside almost exclusively in massive E/S0 galaxies. The energy injected by radio jets per unit volume as a function of redshift indicates that Cen A-like radio galaxies have in principle sufficient power to accelerate cosmic rays to ultra-high energies. We also find a significantly enhanced clustering of radio-loud galaxies compared to normal galaxies of the same luminosity. This indicates a causal relation between galaxy environment and jet power, independent of black hole mass.

70. Adaptive optics: from telescopes to microscopes Tim van Werkhoven Leiden Observatory, Leiden University

While most astronomers associate adaptive optics with observational techniques for telescopes only, other fields such as microscopy now also benefit from adaptive optics. Where telescopes attempt to correct for aberrations due to the turbulent atmosphere, adaptive optics in microscopy corrects aberrations caused by tissue inhomogeneities. In scanning microscopy, a sample is illuminated with a near-infrared laser beam that generates auto-fluorescence in the sample. Optimization of the laser beam focus is crucial to obtain high-quality images. We are measuring the specimen-induced aberrations using fringe analysis of interference patterns. This method provides full wavefront information while being less sensitive to unwanted reflections outside the range of interest, thus paving the way for high-speed, real-time adaptive optics correction in microscopes.

49 71. What shapes the Halo Mass Function? Marco Velliscig Leiden Observatory, Leiden University

The Halo Mass Function (HMF) is an important cosmological observable for both theoretical and observational studies. The HMF is also generally computed using Dark Matter (DM) N-body simulations without taking into account the presence and the effects of the baryons. We have used cosmological hydrodynamical simulations to investigate how including baryons and feedback processes such as stellar winds, supernovae and feedback from Active Galactic Nuclei (AGN), can change the shape of the HMF. We have also performed a study comparing the same halo realizations in simulations with different feedback processes, in order to understand how the presence of feedback can modify the mass of a halo and its matter profile. We have found that the Supernova feedback is particularly important in shaping the HMF in the -1 mass range 11 < Log(M200) Msunh < 12.5, with a difference of -3% with respect to the -1 DM-only case. In the mass range 12.5 < Log(M200) Msunh < 14.2, it is the AGN feedback that is responsible for a -6% variation with respect to the DM-only scenario. Furthermore, we have found that, in this high-mass range, the same halo simulated with AGN feedback has 20% less mass with respect to the halo simulated with only DM-particles. Finally, we provide an analytic formula applicable to HMFs derived from DM-only simulations, in order to take into account the effect of the presence of the baryons.

72. UV/X-ray observation of the Seyfert-1 galaxy 1H0419-577 Laura Di Gesu SRON Netherlands Institute for Space Research

The accretion of matter onto a supermassive black hole powers the high energy emission from Active Galactic Nuclei. A widely accepted unified model explains the activity of these objects, which may have a major influence on the surrounding environment and in the evolution of the host galaxy. Photoionized gas outflows are commonly detected in AGN X-ray and UV spectra,and multiwavelength UV/X-ray campaigns represent the most suitable tool to study the physics of this gas. We present here the results of the recent UV (HST/COS) and X-ray (XMM/RGS) campaign of the Seyfert-1 galaxy 1H0419-577. An outflow was detected in the UV, with three different kinematic components. We detected a thin, lowly ionized absorber in the X-ray spectrum consistent with the ionization of the UV absorber. The emitting gas is not consistent to be the same as absorbing gas. We found also no consistence between the gas emitting the UV lines and the one emitting the X-ray lines,suggesting that they arise in different regions of the AGN.

50 73. ExPo Adaptive Optics Laurens Homs Universiteit Utrecht

The Extreme Polarimeter (ExPo) is an imaging polarimeter optimized for that goal and is able to achieve a contrast of 10-4 with polarimetry alone on the seeing limited William Herschel Telescope. An AO assisted coronagraph will bring contrast ratios at which lower-mass exoplanets can be imaged directly within reach. The experience gained with ExPo and the polarization optimized AO system can be applied to the design and development of the next generation imaging polarimeters to deliver contrasts of up to 10-9 and better.

74. Classification of Atlas3D galaxies Nancy Irisarri Kapteyn Astronomical Institute, University of Groningen

We present a study of the classification of galaxies by applying several methods to the Atlas3D parent sample, which consists of 871 galaxies morphologically classified into 260 early-type galaxies (ETGs) and 611 spiral galaxies. After obtaining photometric parameters from the SDSS catalog for 83% of the parent sample (221 ETGs and 503 spirals), we employ cuts in axis ratio, Sersic index, and concentration. The results show that, choosing from these parameters, the best way to separate the types can be achieved at a concentration value ~2.9. However, significant overlap is found for concentration values in the range 2.8-3.2. Therefore we require quantitative morphology methods to extract the differing structural parameters of a number of galaxies with such concentration values. The methods we study can be harnessed when working with large data sets and with observations of galaxies at high redshift where traditional classification methods are hard to apply.

75. Unraveling the accretion history of an intermediate-mass YSO Lucas Ellerbroek Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Understanding the formation process of high-mass (> 8 Msun) stars is one of the key questions in astronomy. New theoretical results indicate that high-mass stars can form through disk accretion, like low-mass stars. However, this is rarely observed because of the obscuration and small number of young high-mass stars. Intermediate-mass (2 - 8 Msun) stars are a good probe of high-mass star formation: they test the limits of low- mass star formation theory, yet they are less embedded than the more massive objects. We have observed a sample of intermediate-mass Young Stellar Objects (YSO) with the new X-shooter spectrograph on the ESO Very Large Telescope, which covers the full optical to near-infrared wavelength range in one shot. The object 08576nr292 is an intermediate-mass YSO with a disk, driving a Herbig-Haro jet (HH 1042). Using spectroscopic diagnostics, both the kinematics of and physical conditions in the jet can be measured. The kinematics contain a fossil record of the episodic outflow (and accretion) history. This can be simulated by a simple model, resulting in a two-mode sinusoidal outflow rate. The associated timescales are explained by the episodic nature of the accretion and jet-launching process.

51 PARTICIPANTS LIST

Flor Allaert Astronomical Observatory, University of Gent [email protected] Amin Aminaei Radboud University, Nijmegen [email protected] Heather Andrews Leiden Observatory, Leiden University [email protected] Stefano Antonellini Kapteyn Astronomical Institute, University of Groningen [email protected] Giambattista Aresu Kapteyn Astronomical Institute, University of Groningen [email protected] Montserrat Armas Padilla Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Julija Bagdonaite Department of physics and astronomy, VU Amsterdam [email protected] David Baneke VU Amsterdam [email protected] Jeroen Bédorf Leiden Observatory, Leiden University [email protected] Babs Beemster Leiden Observatory, Leiden University [email protected] Casper Blokzijl Kapteyn Astronomical Institute, University of Groningen [email protected] Tatiana Bocanegra JIVE Joint Institute for VLBI in Europe [email protected] Tjarda Boekholt Leiden Observatory, Leiden University [email protected] Wilfried Boland Leiden Observatory, Leiden University [email protected] Patrick Bos Kapteyn Astronomical Institute, University of Groningen [email protected] Niels Bos Kapteyn Astronomical Institute, University of Groningen [email protected] Jeffrey Bout Kapteyn Astronomical Institute, University of Groningen [email protected] Bernhard Brandl Leiden Observatory, Leiden University [email protected] Sjors Broersen Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Matteo Brogi Leiden Observatory, Leiden University [email protected] Anthony Brown Leiden Observatory, Leiden University [email protected] Hugo Buddelmeijer Kapteyn Astronomical Institute, University of Groningen [email protected] Axel Buddendiek Leiden Observatory, Leiden University [email protected] Hans Buist Kapteyn Astronomical Institute, University of Groningen [email protected] Stijn Buitink KVI - RUG [email protected] Sander Bus Kapteyn Astronomical Institute, University of Groningen [email protected] Eva Busekool Kapteyn Astronomical Institute, University of Groningen [email protected] Giorgia Busso Leiden Observatory, Leiden University [email protected] Franka Buurmeijer Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Peter Camps Astronomical Observatory, University of Gent [email protected] Dario Carbone Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Pablo Castellanos Nash Leiden Observatory, Leiden University [email protected] Marius Cautun Kapteyn Astronomical Institute, University of Groningen [email protected] Yuri Cavecchi Leiden Observatory, Leiden University [email protected] Yvette Cendes Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Omar Choudhury Kapteyn Astronomical Institute, University of Groningen [email protected] Nicola Clementel Leiden Observatory, Leiden University [email protected] Thijs Coenen Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Arthur Corstanje Astronomy Department, Radboud University Nijmegen [email protected] Nick Cox Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Caroline D'Angelo Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Martina D’Angelo Zernike Institute for Advanced Materials, University of Groningen [email protected] Erwin de Blok ASTRON Netherlands Institute for Radio Astronomy [email protected] Thomas de Boer Kapteyn Astronomical Institute, University of Groningen [email protected] Gert De Geyter Astronomical Observatory, University of Gent [email protected] Kenneth de Smedt Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Martin de Valois Leiden Observatory, Leiden University [email protected] Ben de Vries Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Vincent Dekker Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Bertrand Delforge SRON Netherlands Institute for Space Research [email protected] Jacqueline den Hartogh Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Laura Di Gesu SRON Netherlands Institute for Space Research [email protected] Matthijs Dries Kapteyn Astronomical Institute, University of Groningen [email protected] Lars Driessen Astronomy Department, Radboud University Nijmegen [email protected] Dmitry Duev JIVE Joint Institute for VLBI in Europe [email protected] Lars Einarsen Astronomical Institute University Utrecht [email protected] Chris Elenbaas Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Lucas Ellerbroek Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] J. Emilio Enriquez Astronomy Department, Radboud University Nijmegen [email protected] Gleb Fedoseev Leiden Observatory, Leiden University [email protected] Nicola Fitzsimons Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Jeroen Franse Leiden Observatory, Leiden University [email protected] Mattia Fumagalli Leiden Observatory, Leiden University [email protected] Katinka Gereb Kapteyn Astronomical Institute, University of Groningen [email protected] Neeraj Gupta ASTRON Netherlands Institute for Radio Astronomy [email protected] Adrian Hamers Utrecht University [email protected] Olga Hartoog Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Brynmor Haskell Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Arisa Hatagaya Leiden Observatory, Leiden University [email protected] Marijke Haverkorn Astronomy Department, Radboud University Nijmegen [email protected] Martin Heemskerk Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected]

52 Stephanie Heikamp Leiden Observatory, Leiden University [email protected] Rosina Hein Bertelsen Kapteyn Astronomical Institute, University of Groningen [email protected] Frank Helmich SRON Netherlands Institute for Space Research [email protected] Godelieve Hensberge Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Ricardo Herbonnet Leiden Observatory, Leiden University [email protected] Johan Hidding Kapteyn Astronomical Institute, University of Groningen [email protected] Michel Hillen Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Jens Hoeijmakers Leiden Observatory, Leiden University [email protected] Laurens Homs Universiteit Utrecht [email protected] Folkert Huizinga Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Boudewijn Hut Kapteyn Astronomical Institute, University of Groningen [email protected] Nancy Irisarri Kapteyn Astronomical Institute, University of Groningen [email protected] Frank Israel Leiden Observatory, Leiden University [email protected] Shoko Jin Kapteyn Astronomical Institute, University of Groningen [email protected] Kimberly Jongman Utrecht University [email protected] Maithili Kalamkar Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Inga Kamp Kapteyn Astronomical Institute, University of Groningen [email protected] Lex Kaper Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Sanaz Kazemi Kapteyn Astronomical Institute, University of Groningen [email protected] Maja Kazmierczak SRON Netherlands Institute for Space Research [email protected] Theo Khouri Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Pamela Klaassen Leiden Observatory, Leiden University [email protected] Georgi Kokotanekov Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Leon Koopmans Kapteyn Astronomical Institute, University of Groningen [email protected] Visa Korkiakoski Leiden Observatory, Leiden University [email protected] Evgenia Koumpia Kapteyn Astronomical Institute, University of Groningen, SRON [email protected] Luuc Kraak Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Maria Krause Astronomy Department, Radboud University Nijmegen [email protected] Mayuresh A. Kulkarni Leiden Observatory, Leiden University [email protected] Robert Laing ESO [email protected] Thanja Lamberts Leiden Observatory, Leiden University [email protected] Rudolf Le Poole Leiden Observatory, Leiden University [email protected] Federico Lelli Kapteyn Astronomical Institute, University of Groningen [email protected] Bertrand Lemasle Kapteyn Astronomical Institute, University of Groningen [email protected] Konstantinos Leventis Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Noel Lopez Gonzaga Leiden Observatory, Leiden University [email protected] Jan Lub Leiden Observatory, Leiden University [email protected] Koen Maaskant Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Elizabeth Mahony ASTRON Netherlands Institute for Radio Astronomy [email protected] Carmen A. Martinez Barbosa Leiden Observatory, Leiden University [email protected] Anna Faye Mc Leod Astronomy Department, Radboud University Nijmegen [email protected] Sofia Meneses-Goytia Kapteyn Astronomical Institute, University of Groningen [email protected] Gerjon Mensinga Kapteyn Astronomical Institute, University of Groningen [email protected] Jonathan Menu Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Michiel Min Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Guifre Molera Calve JIVE Joint Institute for VLBI in Europe [email protected] Remi Monceau-Baroux CPA laboratory - Katholieke universiteit Leuven [email protected] Moein Mosleh Leiden Observatory, Leiden University [email protected] Gijs Mulders Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Anna Nelles Astronomy Department, Radboud University Nijmegen [email protected] Mikkel Nielsen Astronomy Department, Radboud University Nijmegen [email protected] Jan Noordam ASTRON Netherlands Institute for Radio Astronomy [email protected] Parisa Noorishad Kapteyn Astronomical Institute, University of Groningen [email protected] Bram Ochsendorf Leiden Observatory, Leiden University [email protected] Okan Okkuscu Utrecht University [email protected] Paula Andrea Ortiz Otalvaro Leiden Observatory, Leiden University [email protected] Jan Willem Pel Kapteyn Astronomical Institute, University of Groningen [email protected] Stephan Peters Kapteyn Astronomical Institute, University of Groningen [email protected] Yurii Pidopryhora JIVE Joint Institute for VLBI in Europe [email protected] Maura Pilia ASTRON Netherlands Institute for Radio Astronomy [email protected] Mathias Polfliet Astronomical Observatory, University of Gent [email protected] Gergo Popping Kapteyn Astronomical Institute, University of Groningen [email protected] Pratyush Pranav Kapteyn Astronomical Institute, University of Groningen [email protected] Peeyush Prasad Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Jaya Ramchandani Leiden Observatory, Leiden University [email protected] Oscar Ramirez Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Stefano Rapisarda Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Alex Richings Leiden Observatory, Leiden University [email protected] Steven Rieder Leiden Observatory, Leiden University [email protected] Daniel Risquez Leiden Observatory, Leiden University [email protected] Peter Roelfsema SRON Netherlands Institute for Space Research [email protected] Evert Rol [email protected] Rob Rutten Lingezicht Astrophysics [email protected] Waad Saftly Astronomical Observatory, University of Gent [email protected] Francisco Salgado Leiden Observatory, Leiden University [email protected] Irene San Jose Garcia Leiden Observatory, Leiden University [email protected] Robyn Sanderson Kapteyn Astronomical Institute, University of Groningen [email protected]

53 Pim Schellart Astronomy Department, Radboud University Nijmegen [email protected] Harm J. Schoonhoven [email protected] Wouter Schrier Leiden Observatory, Leiden University [email protected] Johannes Schulz Astronomy Department, Radboud University Nijmegen [email protected] Aleksandar Shulevski Kapteyn Astronomical Institute, University of Groningen [email protected] Asa Skuladottir Kapteyn Astronomical Institute, University of Groningen [email protected] Roy Smits ASTRON Netherlands Institute for Radio Astronomy [email protected] David Sobral Leiden Observatory, Leiden University [email protected] Tjitske Starkenburg Kapteyn Astronomical Institute, University of Groningen [email protected] Tomas Stolker Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Caroline Straatman Leiden Observatory, Leiden University [email protected] Judith ter Horst Kapteyn Astronomical Institute, University of Groningen [email protected] Sander ter Veen Astronomy Department, Radboud University Nijmegen [email protected] Satyendra Thoudam Astronomy Department, Radboud University Nijmegen [email protected] Silvia Toonen Astronomy Department, Radboud University Nijmegen [email protected] Scott Trager Kapteyn Astronomical Institute, University of Groningen [email protected] Frank Tramper Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Monica Turner Leiden Observatory, Leiden University [email protected] Phil Uttley Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Jeroen van Asten Astronomy Department, Radboud University Nijmegen [email protected] Ilse van Bemmel ASTRON Netherlands Institute for Radio Astronomy [email protected] Klaas van Berkel University of Groningen [email protected] Caroline van Borm Kapteyn Astronomical Institute, University of Groningen [email protected] Martin van den Akker Astronomy Department, Radboud University Nijmegen [email protected] Brigit van der Hulst [email protected] Thijs van der Hulst Kapteyn Astronomical Institute, University of Groningen [email protected] Piet van der Kruit Kapteyn Astronomical Institute, University of Groningen [email protected] Floris van der Tak SRON Netherlands Institute for Space Research [email protected] Theo van Grunsven SRON Netherlands Institute for Space Research [email protected] Lennart van Haaften Astronomy Department, Radboud University Nijmegen [email protected] Joeri van Leeuwen ASTRON Netherlands Institute for Radio Astronomy [email protected] Pim van Oirschot Astronomy Department, Radboud University Nijmegen [email protected] Thijs van Putten Astronomical Institute 'Anton Pannekoek', University of Amsterdam [email protected] Jan van Roestel Astronomy Department, Radboud University Nijmegen [email protected] Sjoert van Velzen Astronomy Department, Radboud University Nijmegen [email protected] Tim van Werkhoven Leiden Observatory, Leiden University [email protected] Hugo van Woerden Kapteyn Astronomical Institute, University of Groningen [email protected] Sebastiaan Vandewoude Astronomical Observatory, University of Gent [email protected] Harish Vedantham Kapteyn Astronomical Institute, University of Groningen [email protected] Marco Velliscig Leiden Observatory, Leiden University [email protected] Sebastien Viaene Astronomical Observatory, University of Gent [email protected] Joris Vos Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Rasmus Voss Astronomy Department, Radboud University Nijmegen [email protected] Christoffel Waelkens Institute of Astronomy, Katholieke Universiteit Leuven [email protected] Ke Wang Kapteyn Astronomical Institute, University of Groningen [email protected] Paul Wesselius SRON Netherlands Institute for Space Research [email protected] Wendy Williams Leiden Observatory, Leiden University, ASTRON [email protected] Michael Wise ASTRON Netherlands Institute for Radio Astronomy [email protected] Jun Yang JIVE Joint Institute for VLBI in Europe [email protected] Saleem Zaroubi Kapteyn Astronomical Institute, University of Groningen [email protected] Hennie Zondervan Kapteyn Astronomical Institute, University of Groningen [email protected] Jackie Zwegers Kapteyn Astronomical Institute, University of Groningen [email protected]

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