December 2012

14/12/12 (Friday)
12:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lunch Talk
Talk — The physics of massive-star magnetism explored through the MiMeS and BinaMIcS large projects
Gregg Wade (Royal Military College of Canada)

Abstract

Since 2008, the Magnetism in Massive Stars (MiMeS) large programs at ESO, TBL and CFHT have led to a transformation of our understanding of the phenomenon of magnetism in hot OB stars. Starting in 2013, the new Binarity, Magnetism and Interactions in Stars (BinaMIcS) project will bring a fundamental new ingredient to these investigations: the influence and importance of close binarity on massive-star magnetism, and the unique interactions that result thereby. In this presentation I will review the results of the MiMeS survey, discussing in particular the properties of newly-discovered magnetic O-type stars, and introduce the scope and objectives of the BinaMIcS project.
04/12/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Evolution in galaxy cluster cores since z=1
Claire Burke (Liverpool John Moores University)

Abstract

The central regions of galaxy clusters are usually dominated by a massive brightest cluster galaxy (BCG), which generally sits at the centre of mass of the cluster, and a diffuse halo of intracluster light which can be extend beyond the cluster limits. BCGs are the most massive, most luminous galaxies observed in the Universe and their unique positions at cluster centres make them ideal for studying the buildup of large scale structures. A significant fraction of the total baryonic mass and luminosity of galaxy clusters is thought to be contained within the intracluster light (ICL), and the study of the ICL can reveal details of the evolution histories and processes occurring within galaxy clusters. I will review the current theory on the formation and evolution of these most massive galaxies and present the results of our recent observational studies on the evolution of BCGs and the ICL between half way back to the big bang and the present. Our studies show that BCGs are almost fully assembled half way back to the big bang and show almost no evolution up to the present day, in stark contrast to the predictions of cosmological simulations which state that BCGs should double in mass over the this time. The ICL, however, shows substantial growth and evolution over this time. These results point to a rapid early assembly of massive galaxies in clusters followed by passive evolution, with interactions between galaxies in clusters mainly occurring by stripping to build up the ICL at later times.

November 2012

27/11/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Cosmic chronometers: a new approach to constrain the expansion history of the Universe
Michele Moresco (University of Bologna)

Abstract

The determination of the expansion history of the Universe is one of the most crucial measurements for cosmology, since the rate at which it decelerates/accelerates directly depends on the energy components which characterize it (and, in particular, the "dark energy", in case of an accelerated expansion). It is therefore fundamental to measure it, i.e. the Hubble parameter H(z), very precisely. In this talk I will present an innovative method to obtain direct constraints on H(z) from the differential age evolution of cosmic chronometers. I will provide the basic theoretical background of this approach, and I will as well discuss its dependence on assumptions and systematics. The "cosmic chronometers" approach has been recently used to obtain new high-accuracy measurements of H(z) up to z~1.1 from the analysis of a large sample of massive and passive ETGs. I will present these results, focusing the attention in particular to their cosmological consequences, showing the potentiality of this technique to discriminate amongst different cosmologies. I will also demonstrate that this approach can be not only complementary, but also competitive with the other "standard" probes, i.e. SNe and BAO.
20/11/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — The role of the structure formation process in regulating the galaxy star formation activity
Paola Popesso (MPE)

Abstract

Achieving an observational determination and a theoretical understanding of the Cosmic Star Formation History (CSFH) of the Universe is one of the biggest challenges in the study of galaxy formation and evolution. The most striking feature of the CSFH is a dramatic drop of the star formation rate, since z~1 to the present day, after a rather constant phase of high activity at z~1-2 or above. A quenching process is required to trigger such an abrupt decrease of the Star Formation (SF) activity. As a matter of fact, the progressive decline of the SF activity of the Universe since z~1 anti-correlates with the late-time increase of the number density of group-sized halos. It is, then, mandatory to follow this tantalizing lead and to ask if the very same process of assembly and growth of structures may be the main cause, or one of the major drivers, of the 1 order of magnitude decline in the CSFH. I will tackle this issue by showing that group galaxies evolve much faster than galaxies in low density regions. Star forming group galaxies, in particular, are perfectly on the Main Sequence (MS) at z~1 whereas at lower redshift they are quenched, thus, dropping off the MS quicker than field galaxies towards the region of SF quiescence. I will also show that the efficiency of the quenching process depends on the halo mass, being more efficient in the most massive halos, and thus, in most massive galaxies that tend to reside in such halos.
06/11/12 (Tuesday)
13:00, D29 | ESO Garching
Lunch Talk
Talk — The CO connection to the radio-FIR correlation in M51
Gaelle Dumas (IRAM, France)

Abstract

I will present first results of the PdBI Arcsecond Whirlpool Survey (PAWS, PI E. Schinnerer). PAWS has imaged the CO(1-0) emission in the central 8 kpc of the nearby galaxy M51. Our final data is a combination of the IRAM 30m single-dish and PdBI observations. It reaches a resolution of about 40pc and is sensitive to Giant Molecular Clouds (GMCs) above 10^5 Msun. This data allow us to study in great details the properties of the GMCs in this galaxy and in particular we investigate the relations of the molecular gas to other tracers of the ISM. In this talk I will present a study of the relation between the CO emission, the radio continuum and the IR emission as a function of galactic environment. I'll discuss these results in the context of cosmic ray electrons diffusion and its relation to the star formation processes.

October 2012

30/10/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Star formation in nearby young clusters
Catarina Alves de Oliveira (Herschel Science Centre (ESA))

Abstract

The rapid advances in infrared detector technology over the past decades have impelled the development of wide-field instruments, and shaped our view of the cold universe. Large infrared and submillimeter surveys of nearby star-forming regions in our Galaxy can pierce the obscuring dust to reveal embedded young stars and protoplanetary disks, and also uncover the cold large-scale structure of molecular clouds. I will present results from two projects based on such datasets, namely, i) to constrain the formation scenarios of substellar objects, and ii) study the connection between filamentary structure and star formation activity. In the first project, we make use of a deep WIRCam/CFHT imaging survey of two young clusters (Rho Oph and IC348) to uncover candidate substellar members. Through an extensive spectroscopic follow-up (using SofI/NTT, NICS/TNG, ISAAC/VLT, Osiris/GTC, and GNIRS/Gemini) we derive a reliable census of their substellar population down to a few Jupiter masses, which is used to study the initial mass function, mass segregation, and the properties of brown dwarf disks using new PACS/Herschel observations. In the second project, we use Herschel observations of the Chamaeleon molecular cloud complex, which contains three dark clouds with a dramatically different star formation activity, to investigate the connection between the properties of its filamentary structure and the on-set of star formation.
26/10/12 (Friday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — The interplay between molecular and ionized gas surrounding massive embedded stars
Katharine Johnston (MPIA Heidelberg)

Abstract

Although there is much evidence that B-stars (~3-15 Msun) form similarly to their low-mass counterparts, the picture is not so clear for O-stars. In this talk I present studies of two highly luminous (>10^5 Lsun) embedded O-star precursors, AFGL2591 and AFGL4176. Our aims were to determine whether the properties of these forming stars, such as the circumstellar structure, outflow and jet could be described satisfactorily by the properties of low-mass protostars, and to understand how the formation of an HII region may interrupt accretion or outflow onto/from the forming star. To this end, we used a variety of cm and mm interferometric observations to trace both the molecular and ionized gas. In addition, I will present our current results from radiative transfer modelling of these two sources, which provide insight into the density and velocity structure of their circumstellar material.
12/10/12 (Friday)
12:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lunch Talk
Talk — Title: Kinematic structure and metallicity distribution of the Carina dSph galaxy
Michele Fabrizio (University of Rome "Tor Vergata")

Abstract

Dwarf galaxies are the crossroad of significant theoretical and observational efforts, but we still lack firm constraints concerning their formation and evolution. They are also fundamental laboratories to investigate the impact of the environment on chemical evolution in stellar systems with total masses between giant galaxies and globular clusters. We present accurate iron abundance measurements for 44 red giants (RGs) in the Carina dwarf spheroidal galaxy using high-resolution spectra (R~38,000) collected with UVES at ESO/VLT. For the 27 stars for which we measured both [FeI/H] and [FeII/H] abundances, we found evidence of NLTE effects between neutral and singly-ionized iron abundances. We also present recent results concerning the kinematics properties of the Carina dwarf spheroidal. We performed precise radial velocity (RV) measurements of two thousands of stars covering the entire body of the galaxy. The individual spectra (21,340) were collected using FORS2 (low-), GIRAFFE (medium- and high-) and UVES (high-resolution) at the VLT. The RV distribution of the ~1,370 candidate Carina stars indicates the occurrence of secondary features across the galactic center. These findings are reminiscent of a substructure with transition properties, already detected in dwarf ellipticals, and call for confirmation by independent investigations.
09/10/12 (Tuesday)
12:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lunch Talk
Talk — The SMC in space and time: star formation history of a prototype dwarf irregular galaxy
Monica Tosi (INAF - Astron. Obs. Bologna)

Abstract

The SMC is an excellent benchmark for galaxy evolution studies, both as the closest representative of galaxies of the most diffuse morphological type, dwarf irregulars, and as member of the closest triple galaxy system. I will present our recent studies of the SFH of several regions of the SMC. These results are currently based on HST photometry, to be soon complemented with a complete and deep photometric coverage of the galaxy performed with VST-GTO. They are part of a multi-fold project aimed at deriving information on the evolution of the SMC and of dwarf galaxies in general.
02/10/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Deep 21-cm HI Observations with the Arecibo Telescope
Laura Hoppmann (ICRAR and Univ. of Western Australia)

Abstract

The star formation rate (SFR) in galaxies, as measured by optical, UV and far-infrared observations, appears to increase by an order of magnitude over the redshift interval of z=0 to z≈1. However, little accurate information about the co-evolution of neutral hydrogen is available. Measurements are limited to sparse and model-dependent observations of damped Lyman-α systems at high redshifts or to observations of 21cm radio emission line at very low redshift. However, the unique sensitivity of the Arecibo telescope can be used to directly detect 21-cm HI emissions from galaxies at cosmological distances. Previous detections have involved optically pre-selected galaxies and are therefore biased in their selection criteria. Here we present results from the ongoing Arecibo Ultra Deep Survey (AUDS) which is a blind 21-cm survey with the Arecibo L-band Feed Array (ALFA). We use data from AUDS to accurately derive the HI mass function and constrain the cosmic HI density ΩHI at redshifts greater than zero for the first time.

September 2012

25/09/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — A History of Photosynthesis Research, 1840-1960
Kärin Nickelsen (LMU Munich)

Abstract

Photosynthesis is known as the process by which green plants utilize the energy of sunlight to produce carbohydrates from carbon dioxide and water in the green parts of the plant. It is fundamental to life on earth, and the way organisms accomplish this task has intrigued scientists for centuries. The first tentative (and rather simplistic) ideas were developed by organic chemists around 1840, while by 1960 an elaborate photosynthesis model at a molecular level had been established, encompassing a set of light reactions, with two different photochemical systems, which was linked to a light-independent sequence of dark reactions via a cyclic pathway. The paper outlines important milestones of this development, while it pays particular attention to the factors that drove the research in one direction or other.
18/09/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Pre-main sequence stars in clusters: from Orion to the Magellanic Clouds
Nicola Da Rio (ESTEC)

Abstract

The study of low mass, pre-main sequence (PMS) stars in clusters is critical for our understanding of the star formation process, and the initial mass function. Specifically, since PMS stars slowly contract towards the main sequence, they are natural tracers of the duration of star formation. Moreover, these objects are brighter than more evolved stars for the same mass, enabling us to detect them more easily well below the H-burning limit. Unfortunately, this is not without problems, and the uncertainties still remain large. I will describe some of my recent results in the field, focusing on the young stellar population in the Orion Nebula Cluster and in young regions of the Magellanic Clouds. I will mostly focus on issues and results related to the IMF in the very low-mass and brown dwarf regime, the long standing problem of the age spreads in young clusters, and the understanding of the time evolution of mass accretion rates.
11/09/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Probing the early stages of planet formation with ALMA and other sub-mm interferometers
Luca Ricci (Caltech)

Abstract

Observations of protoplanetary disks at sub-mm wavelengths trace mm-sized dust grains in the disk outer regions. Models of the early stages of planet formation, including growth and radial migration of dust grains in the disk, can therefore be tested by these data. I will outline the state-of-the-art of this field by presenting old and new data obtained with CARMA, PdBI, ATCA and EVLA interferometers for a large sample of young disks in nearby star forming regions. I will show how very-low mass disks are particularly suitable to test the model predictions and investigate the physics of solids evolution in disks. This is currently being investigated through undergoing observations with ALMA of four disks around brown dwarfs and very low-mass young stars. I will present the first results from this project and outline in which aspects future ALMA observations can play a key role in our understanding of planetesimal formation.

August 2012

07/08/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Herschel, Planck and the High Redshift Universe
David Clements (Imperial College London)

Abstract

The far-IR/submm band from 200 to 500 microns has been largely unexplored until very recently. Since their launch, in May 2009, Herschel and Planck have been exploring this waveband and providing new insights into a wide range of astrophysics. This talk focuses on the high redshift (z>1) universe and will discuss gravitational lenses, galaxy clusters and the search for the highest redshift dusty galaxies. It is still early days for the exploitation and followup of Herschel and Planck surveys, but it is already clear that these missions will have a major impact on our understanding of dusty galaxies at high redshift.

July 2012

31/07/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Exploring the Ursa Major Region
Kathrin Wolfinger (Swinburne University, Australia)

Abstract

The Ursa Major region is an ideal target to study the effect of environment on the evolution of gas-rich galaxies as it is nearby and most of the known member galaxies are late-type galaxies that are rich in neutral hydrogen (HI). We investigate 480 deg^2 and a heliocentric velocity range of 300-1900 km/s using data from the HI Jodrell All Sky Survey (HIJASS). The region includes the Ursa Major cluster (17.1 Mpc; Tully et al. 2008), the Canes Venatici groups (4.1 Mpc; Karachentsev et al. 2003) and the less dense filament connecting the Ursa Major and Virgo cluster (16.7 Mpc; Kent et al. 2007). I will present an overview of the region: (i) the peak-flux limited catalogue containing 155 HI sources, 13 of which are first time detections in HI including a candidate galaxy/tidal tail/HI bridge, (ii) intriguing objects such as HIJASS detections with HI extensions/plumes and (iii) candidate regions for galaxy-galaxy interactions. Furthermore I will show preliminary results from our study regarding substructures in the region and their dynamics.
24/07/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — A near-infrared spectroscopic survey of star-forming galaxies and AGNs with Subaru/FMOS
John Silverman (Kavli Institute for the Physics and Mathematics of the Universe )

Abstract

I will discuss a new 'intensive' survey of star-forming galaxies in COSMOS using the Fiber Multi-object Spectrograph (FMOS) on the Subaru Telescope. FMOS is a multi-fiber instrument capable of simultaneously obtaining near-infrared spectra (1-1.8um) of a few hundred galaxies thus enabling a large redshift survey across a previously challenging redshift regime (1.2 < z < 1.8). Our survey is designed to detect Halpha in emission in order to establish the evolution of the SFR-Mstar relation and any dependence on environment. I will also highlight galaxies detected by Hershel/PACS and AGNs selected by their X-ray emission.
17/07/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Physical properties of distant galaxies under the cosmic microscope
Johan Richard (CRAL, Observatoire de Lyon)

Abstract

I will present recent observational results obtained on the physics of distant galaxies (~ 1
10/07/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Exploring the phase space structure of the Milky Way halo with stellar orbits
Monica Valluri (University of Michigan)

Abstract

Resolved surveys of the Milky Way's stellar halo can obtain all 6 phase space coordinates of tens of thousands of individual stars, making it possible to compute their 3-dimensional orbits. The "orbital spectral analysis" technique can be applied to halo orbits to construct frequency maps which are a compact, yet informative representation of the halo phase space distribution function. Frequency maps visually represent the major types of orbit families that constitute the stellar halo and their relative importance. Analysis of simulations shows that even when halos are quite close to oblate, a large fraction of orbits have the characteristics of orbits in triaxial systems. The structure of the frequency maps, especially the resonant orbits, reflects the formation history and shape of the dark matter potential and its orientation relative to the Galactic disk. The application of frequency analysis to cosmological hydrodynamic simulations of disk galaxies shows that the orbital families occupied by halo stars and dark matter particles are very similar. An application of these methods to a sample of ~17,000 Milky Way halo stars from the SDSS-SEGUE-II survey yields a frequency map with strong evidence for resonant trapping of halo stars by the Milky Way disk. The observed resonances in frequency maps of SEGUE stars point to a fairly quiescent history for the Milky Way. The application of frequency analysis methods orbits of Milky Way halo stars (e.g. from the upcoming Gaia mission) will provide new insights into the formation history of the halo.

June 2012

26/06/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Interaction of free-floating planets with a star-planet pair
Harry Varvoglis (University of Thessaloniki & University of Tübingen)

Abstract

The recent discovery of free-floating planets in the Milky Way introduced an intriguing possibility. Namely, that some exoplanets are not condensed from the protoplanetary disk of their parent star. In this novel scenario a free-floating planet interacts with an already existing planetary system and is captured as a new planet. In the present work we study this interaction process by integrating trajectories of planet-sized bodies, which encounter a binary system consisting of a Jupiter-sized planet revolving around a Sun-like star. The possible final outcomes of this interaction are only four, namely flyby, planet exchange, capture or disruption. We show that the process is a classical scattering problem with fractal properties. We find that the probability of exchange or capture (in prograde as well as retrograde orbits) is non-negligible, a fact that might possibly explain observations of planetary systems with orbits that are either retrograde or tight and highly eccentric.
19/06/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Shedding light on CANDELS
Audrey Galametz (Rome Observatory, INAF)

Abstract

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS; PIs: H. Ferguson, S. Faber; Grogin et al. 2011; Koekemoer et al. 2011) is the largest project in the history of Hubble (902 orbits). It will document the first third of galactic evolution from z = 8 to 1.5 via deep imaging of ~250,000 galaxies with HST WFC3/IR and ACS. It will also permit to find the first Type Ia SNe beyond z > 1.5. CANDELS is currently observing 5 fields (selected for their existing multiwavelength data e.g. ground-based, Spitzer and spectroscopy), GOODS-N and GOODS-S, UDS, COSMOS and EGS at two distinct depths (a.k.a `CANDELS-Deep' and `CANDELS-Wide'). CANDELS is a collaboration of more than 100 scientists who will exploit the data to get insights on research topics as diverse as SN, Cosmic High Noon (26; e.g., constrain properties of galaxies at the end of the reionization epoch) etc. In this talk, I will (i) provide a brief overview on the CANDELS survey, (ii) describe observing strategy, data status and first results (iii) introduce the HAWK-I UDS and Goods-S survey (HUGS, PI: A. Fontana, follow-up of CANDELS with VLT/HAWK-I) (iv) present our team work to build public legacy multiwavelength catalogs for each CANDELS field and finally (v) present preliminary work on the search and study of large scale structures within CANDELS.
12/06/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Co-evolving black holes and galaxies
James Mullaney (University of Durham)

Abstract

It is generally accepted that today's massive galaxies contain a central, supermassive black hole with a mass closely related to that of the host. However, how this situation has come about is far from clear. At some level, the growth of black holes and their galaxies must be linked, whether by active (e.g., direct feedback) or passive (e.g., common fuel supply) regulation. In this lunchtalk, I will highlight recent observational results which are beginning to shed light on how black holes and their host galaxies co-evolve and what processes may regulate their growth.
05/06/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Extra-Galactic Planetary Nebulae with Integral-Field Spectroscopy
Marc Sarzi (University of Hertfordshire)

Abstract

Planetary Nebulae (PNe) in external galaxies are mostly regarded either as tracers of the gravitational potential or as indicators for the distance of their galactic hosts, with the latter advantage owing to the almost universal - though not fully understood - shape of the PNe luminosity function (PNLF, generally in the [OIII]5007 emission). Yet extra-galactic PNe can also be used as probes of their parent stellar population and understanding in particular the origin of the PNLF is a puzzle that, once solved, promises to reveal new clues on the late stages of stellar evolution and on the formation of PNe themselves. I will show how integral-field spectroscopy allows to detect PNe in the optical regions of galaxies to flux levels otherwise inaccessible to standard narrow-band photometry. This allows to trace the PNLF in the same galactic regions where the properties of stellar populations can be well characterised, thus making it possible to understand how the shape of PNLF relates to the parent stellar population of PNe. I will present results based on the detailed analysis of SAURON data for M32 and M31, showing for the first time that the PNLF is in fact not universal, and preliminary work on galaxies as far as the Virgo cluster. I will also discuss the future prospect of this field with next generation integral-field units such as MUSE on VLT.

May 2012

22/05/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Dissecting the anatomy of the NGC 2264 G protostellar outflow with the Spitzer InfraRed Spectrograph
Paula Teixeira (University of Vienna)

Abstract

Bipolar molecular outflows and jets are natural by-products of star formation. These outflows deposit a significant amount of energy in their surroundings and help dissipate the circumstellar envelope of their protostar. I will present Spitzer observations of a powerful outflow in the young star forming region NGC2264, located ~900pc away. From the IRAC data, we found that the jet powering the outflow can be described by a precessing model, with a period of ~8000yr. Follow-up observations with the IRS detected atomic and ionic line emission from the underlying jet near the driving source, although most of the emission observed is from pure rotational H2 emission lines. We estimate that the H2 emission is arising from a mixture of gas with temperatures ranging between 1300 and 2500K. The morphology of the outflow, described by the S(0) and S(1) H2 emission is a textbook example of a bow shock and a nose cone, and we find a remarkable spatial correlation between these lines and low- and high-velocity components of the CO(2-1) outflow, respectively.
15/05/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Contemplating the Formation of Sun-like Stars
Doug Johnstone (National Research Council Canada, Herzberg Institute of Astrophysics)

Abstract

Coordinated multi-wavelength surveys of nearby molecular clouds provide useful constraints on the physical conditions within low-mass star-forming regions. In this manner, Perseus and Ophiuchus have been exceptional laboratories for testing the earliest phases of star formation. Highlights of these results are (1) most of the mass of the cloud is at low column density, (2) dense cores form only in high column density regions, (3) the mass distribution of the dense cores is similar to the that observed for stars, (4) dense cores contain only a few percent of the cloud mass, (5) the more massive cores are most likely to contain embedded protostars, and (6) the kinematics of the dense cores and the bulk gas show significant coupling. In this talk, I will mention each of these important results and attempt to place them in context with theoretical models and simulations of star formation.
08/05/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Triggering Quasars
Clive Tadhunter (University of Sheffield)

Abstract

We know surprisingly little about how, when and where quasars are triggered as galaxies evolve. In this seminar I will review quasar triggering mechanisms, and present the results from an optical and far-infrared study of a large sample of luminous radio-loud AGN that cast direct light on the quasar triggering issue, demonstrating that galaxy mergers are the most likely triggering mechanism. Along the way, I will emphasise the importance of taking full account of the AGN-related continuum components when determining the host galaxy properties.

April 2012

24/04/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Extragalactic molecular line surveys
Rebeca Aladro (University College London)

Abstract

Molecular line surveys are excellent tools to study the physical chemical properties of the extragalactic interstellar medium. Recent studies have demonstrated that molecular abundances in the nuclei of galaxies can be used to disentangle the deeply obscured nuclear power sources (AGN or starbursts), as well as to estimate the strength of the UV fields, X rays, and/or shocks affecting the gas. I will review the most important studies done on this field, and show how the physical properties of the ISM can be derived from this chemical studies.
19/04/12 (Thursday)
12:30, Auditorium Telescopium (ESO HQE, Garching) | ESO Garching
Lunch Talk
Talk — Diffuse mid-IR emission: A problem for SFR measures?
Alison Crocker (University of Massachusetts)

Abstract

Emission in the mid-IR (3-30 micron) in star-forming galaxies is mostly due to emission from small dust grains and large molecules. The large molecules, PAHs, emit in several bright bands, while both the large molecules and small grains emit continuum emission, after being heated to high effective temperatures by one or few photons (stochastic heating). These small particles have higher absorption cross-sections in the UV than classical (large) dust grains, theoretically making them a better tracer of young stars than the big grains which are more easily heated by lower-energy photos produced by older stars. However, they might be a less ideal tracer than hoped for due to two factors (1) the small grains/large molecules are largely destroyed in the vicinity of hot, young stars and (2) despite the UV-biased cross-section, the small grains/large molecules may be excited by old stars as well as young stars, particularly when located far from star-forming regions. Here I present work on a few, nearby, star-forming galaxies. By spatially separating the star-forming and non-star-forming regions and taking into consideration both UV photons and stars themselves "leaking" from star-forming regions, the fraction of 8micron dust emission due to old stars is approximately 40%, a large enough fraction to worry about this contribution when considering its use as both a low-redshift (typically resolved) and a high-redshift (at z=2 is in the MIPS 24 micron band) SFR measure. I will also discuss the decline of the 8micron to Halpha emission ratio in both star-forming and diffuse regions, discussing some (metallicity-dependent) reasons for the trends we see.
17/04/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Type Ia Supernovae: Explosions and Progenitors
Wolfgang Kerzendorf (University of Toronto)

Abstract

Type Ia supernovae are known as the precise distance indicators that allowed the remarkable discovery of the accelerated expansion of the universe. Despite this astounding feat, there still remain large uncertainties in many of the key issues surrounding these extremely energetic events. These uncertainties, while not being horribly detrimental to their use as distance indicators, hamper the understanding of the far reaching consequences these cosmic factories of heavy elements have on the chemical evolution of the Universe. Type Ia Supernovae can be divided into three distinct phases. The pre-supernova evolution, the explosion itself and the expansion phase, which results in spectra and light-curves. In this talk I will first presents our findings on the progenitor question (pre-supernova phase). In addition, I will discuss my work on automating spectral analysis and how it links with explosion physics and the progenitor question. Finally, I will briefly highlight Universities of Toronto's involvement in arctic astronomy and introduce our transient search with the telescope CATS.
03/04/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Interstellar polarization: old models and new ideas
Nikolai V. Voshchinnikov (St. Petersburg University, Russia)

Abstract

Interstellar linear polarization is caused by the linear dichroism of the interstellar medium due to the presence of non-spherical oriented grains. The interpretation of polarimetric observations includes computations of the polarization cross sections and averaging of them for given particles size and orientation distributions. Early models dealt with infinite cylindrical particles which were assumed to be perfectly aligned. Such models produce polarization much larger than the observed one. We use the model of spheroidal grains with imperfect alignment. It allows one to estimate the properties of dust grains and the angle between the line of sight and the magnetic field direction, i.e., to find the space structure of magnetic field. The results for Taurus molecular cloud TMC-1 will be demonstrated. The nature of polarizing grains can be established from the comparison of the degree of interstellar polarization P and polarization efficiency P/E(B-V) or P/A(V) with dust phase abundances. We detect an anticorrelation between P and the dust phase abundance of iron in non silicate-containing grains, a correlation between P and the abundance of Si, and no correlation between P/E(B-V) or P/A(V) and dust phase abundances. These findings can be explained if mainly the silicate grains aligned by the radiative mechanism are responsible for the observed interstellar linear polarization.

March 2012

27/03/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Nuclear clusters in late-type dwarf galaxies in low-density environments
Iskren Georgiev (AIfA, Bonn)

Abstract

Massive star clusters in the nuclear regions of dwarf (irregular) galaxies have been envisioned as possible progenitors of a sub-population of peculiar Galactic globular clusters, e.g. wCen, NGC 2419, M54. The latter is still associated with the nucleus of the dissolving Sagittarius dSph. It is however not well known, how the properties of massive nuclear clusters in such dwarf galaxies compare to those of these Galactic GCs. A common origin, i.e. in a deep potential, will result in a similar evolution of their stellar populations and structural properties. I will present such an analysis based on a large sample of nuclear clusters in dwarf irregular galaxies studied with HST imaging and VLT spectroscopy and supplemented by new (still in progress) analysis of B,V,I VIMOS imaging of 10 LMC mass dIrrs, located in the outskirts of Fornax and Eridanus galaxy clusters.
20/03/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — News from the merger remnant NGC 1316 (Fornax A)
Tom Richtler (Universidad de Concepcion, Chile)

Abstract

I shall present results from recent photometric and spectroscopic work on the merger remnant NGC 1316 and its globular clusters (GCs). Wide-field imaging in the Washington system reveals morphological details which previously have gone unnoticed. The distribution of GC colors indicates an extended period of star cluster formation. The kinematics of about 170 GCs show a complex behavior, complicating a dynamical analysis. Finally, I briefly present the remarkable object SH2 in NGC 1316 which may be an infalling dwarf galaxy.
13/03/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Density waves in debris disks
Mir Abbas Jalali (Sharif University of Technology)
06/03/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — The MIDI AGN Large Programme: A statistical sample of resolved AGN tori
Leonard Burtscher (MPE)

Abstract

Interferometric observations with MIDI/VLTI in the mid-infrared made studies of the central dusty tori of Active Galactic Nuclei (AGNs) possible and proved their existence in a number of nearby galaxies. Both type 2 and type 1 galaxies showed dust on the parsec-scale whose general properties were comparable - consistent with (but not proving) the "unifying model" for radio-quiet galaxies. Existing studies were, however, mostly based on single or very few sources and therefore dominated by the characteristics of individual galaxies. For a more comprehensive approach, a larger sample is needed. This statistical basis is set up as a VLTI/MIDI Large Programme that comprises 14 AGNs for which torus properties are being determined. Observations and data reduction are finished and show resolved dust emission in almost all of the sources. They represent the largest sample of resolved AGN tori so far, allowing to ask a number of questions, ranging from unification to the physics of accreting galactic nuclei. In particular, the observations allow us to dissect the parsec-scale infrared emission and to determine the sizes and fluxes of the various components.

February 2012

28/02/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Properties of the AGN wind of Mrk 509
Katrien Steenbrugge (Universidad Catolica del Norte en Antofagasta, Chile)

Abstract

I will present the optical, UV and X-ray data obtained during a 3 month observational campaign of the Seyfert 1 galaxy Mrk 509, using 5 different satellites, and obtained with the goal to determine the mass, kinematic luminosity and feedback on the host galaxy of this outflow. I will focus on the 600 ks XMM-Newton RGS spectrum, which is the deepest high-resolution X-ray spectrum yet of a Seyfert 1 galaxy, and the high signal-to-noise HST-COS UV spectrum. The excellent statistics allow us to study in detail the ionization structure and relative abundances (X-rays) and kinematics (UV) of this gas. The ionization structure spans 3 orders of magnitude and is discrete and the abundance ratios are consistent with solar ratios. We detect absorption from an AGN wind which has 8 different kinematic components and is located at distances between 5 and 400 pc; the host galaxy and probably a high velocity cloud about 22 kpc from Mrk 509.

January 2012

31/01/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — The Star Formation & Chemical Evolution Timescales of Two Nearby Dwarf Spheroidal Galaxies
Thomas de Boer (Kapteyn Astronomical Institute, Groningen)

Abstract

We present the detailed Star Formation History of the nearby Sculptor and Fornax dwarf spheroidal galaxies, from wide-field photometry of resolved stars, going down to the oldest Main Sequence Turn-Off. The accurately flux calibrated, wide-field Colour-Magnitude Diagrams are used directly in combination with spectroscopic metallicities of individual RGB stars to constrain the ages of different stellar populations, and derive the Star Formation History with particular accuracy. The detailed Star Formation History shows the star formation at different ages and metallicities, at different positions in the galaxy, and shows that the known metallicity gradients are well matched to an age gradient. The obtained SFH is used to determine accurate age estimates for individual RGB stars, for which spectroscopic abundances (alpha-elements, r- and s-process elements) are known. In this way, we obtain the accurate age-metallicity relation of each galaxy, as well as the temporal evolution of alpha-element abundances. This allows us to study, for the first time, the timescale of chemical evolution in these two dwarf galaxies, and determine an accurate age of the "knee" in the alpha-element distribution. Finally, we compare the timescale of chemical evolution in both dwarf galaxies, and determine whether the chemical abundance patterns seen in galaxies with recent episodes of star formation are a direct continuation of those with only old populations.
17/01/12 (Tuesday)
12:30, D30 | ESO Garching
Lunch Talk
Talk — The radio sky at 12mm - latest science results from the AT20G survey
Elaine Sadler (University of Sydney)

Abstract

The Australia Telescope 20 GHz (AT20G) survey is a sensitive imaging survey of the entire southern sky (south of declination 0 degrees, at Galactic latitude |b|> 1.5 deg) carried out with the Australia Telescope Compact Array in the 12 millimetre band. The kinds of radio sources seen at 12mm are significantly different from those in seen in lower-frequency radio catalogues like NVSS and FIRST. I will discuss some recent science results from AT20G, including the discovery of a large population of young and recently-restarted radio galaxies. I will also mention some scientific links to the large optical/IR sky surveys currently underway at ESO, the Planck (CMB) and Fermi (gamma-ray) missions, and future work with ALMA.
10/01/12 (Tuesday)
12:30, D29 | ESO Garching
Lunch Talk
Talk — Tales about Supernovae
Jason Spyromilio (ESO)

Abstract

A review of the scientific evolution in the field of supernovae over the past 25 years with an emphasis on work that underpins the use of supernovae as standard candles. Some recent results from the work following on from the original Lambda discovery papers will also be discussed.

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