The relevance of mergers for fueling AGNs: Answers from quasar host galaxy studies

Informal Colloquium
Dr. Nicola Bennert
ORATED
University of California Riverside

The majority of quasars are known to reside in the centers of galaxies that look like ellipticals. Numerical simulations have shown that remnants of galaxy mergers often closely resemble elliptical galaxies. However, the connection between mergers and quasar activity is strongly debated: Did the host galaxies form at high redshift and are now dominated by old bulges or are there signs of recent mergers as in the case of ultra-luminous infrared galaxies? We use deep Keck spectroscopy and HST/ACS imaging to study the connection between starbursts and mergers in quasars which reside in seemingly undisturbed ellipticals. Five objects studied in detail show traces of major starburst episodes and reveal strong signs of interactions (shells, tidal tails, warped disks), one spectacular example being MC2-1635+119. We compare our results with numerical simulations of galaxy mergers to estimate the type and age of the merger. Our results show that at least some quasar host galaxies are the products of relatively recent merger events rather than old galaxies which formed at high redshift.

Studying the interstellar magneto-ionic medium through the Canadian Galactic Plane Survey

Special Colloquium
Dr. Roland Kothes
ORATED
Dominion Radio Astrophysical Observatory, Canada

The Canadian Galactic Plane Survey is a study of the Galactic ecosystem in the outer Milky Way comprising HI and CO observations, reprocessed IRAS surveys, and radio continuum observations in Stokes I at 408 MHz, and Stokes I, Q, and U at 1420 MHz. The CGPS covers an area between Galactic Latitude of -3.5 and +5.5 degrees and Galactic Longitude of 55 and 192 degrees. I will give an overview of the 1420 MHz linear polarization measurements and present new images and some first ideas and results of studies into the local and global magneto-ionic medium.

Magnetic Launching of AGN-Jets

Main Colloquium
Dr. Andreas Müller
ORATED
MPE Garching

AGN jets are powerful, large-scale outflows driven by the central supermassive black hole of luminous active galactic nuclei. This talk summarizes the current status of general relativistic magnetohydrodynamics simulations on the Kerr geometry of spinning black holes. We discuss the jet-disk connection, morphologies at the jet base, the role of black hole spin, and finally aspects of radiative magnetohydrodynamics.

Examining the Evolutionary Sequence of Massive Star Formation

Special Colloquium
Dr. Tracey Hill
ORATED
Leiden Observatory

Despite the attention that massive star formation (MSF) has attracted in recent years, the scenario of their formation is still largely unclear. I will present the results of a millimetre continuum emission study of massive star formation regions associated with methanol maser and UC HII regions, conducted with the SIMBA instrument on the SEST. Interestingly, this SIMBA survey revealed a wealth of sources that are devoid of both methanol maser and radio continuum emission (mm-only), which then formed the basis of a submillimetre continuum emission study with SCUBA on the JCMT. Spectral energy distribution (SED) analysis of the sources in the SIMBA sample revealed clear distinctions between the four classes of source in the sample. The mm-only sample are the coolest and least luminous sources, but are of comparable mass and radius to sources with a methanol maser and/or UC HII region. The mm-only population appears to comprised of two distinct populations distinguished by temperature. The cool-mm sources are distinct from the warm-mm sources as well as from those sources with a methanol maser and/or radio continuum source in terms of luminosity, luminosity-to-mass ratio, radius, H2 number density and the surface density. Conversely, the warm-mm sources are similar to those sources with a methanol maser and/or radio continuum sources for each of these parameters as well as the mass. These results led us to propose an evolutionary sequence for massive star formation involving the mm-only core, where the warm-mm sources are possible precursors to the methanol maser and are thus indicative of the earliest stages of massive star formation, and the cool-mm sources are possible examples of ‘failed’ cores that will remain starless.

Effects of the turbulent ISM on radio observations of quasars

Informal Colloquium
Krisztina Gabanyi
ORATED
MPIfR Bonn

In radio bands, the study of compact radio sources can be affected by propagation effects in the Interstellar Medium. These are usually attributed to the presence of turbulent intervening material along the line of sight. In this talk, two of such effects are presented. The line of sight of B2005+403 passes through the heavily scattered region of Cygnus, which causes substantial angular broadening of the source image between 0.6 GHz and 8 GHz. At higher frequencies however the intrinsic source structure shines through. Therefore multi-frequency VLBI observations allows us, to study the characteristics of the intervening material, the source morphology and the “coupling” of them in forming the observed image. J1128+592 is a newly found highly variable IDV source, with observed timescales ranging between few hours and two days. At present the mixing ratio between source intrinsic and source extrinsic IDV is unclear. One of the strongest evidence in favor of propagation induced IDV would be the annual modulation of the observed variability timescale caused by the Earth orbiting motion around the Sun. So far, the observations of J1128+592 suggest that the changes of its variability timescale can be attributed to annual modulation.

A Radio View at the COSMOS

Main Colloquium
Dr. Eva Schinnerer
ORATED
MPIA Heidelberg

The COSMOS project is a pan-chromatic imaging and spectroscopic survey of a 2 square-degree field designed to probe galaxy and SMBH (super-massive black hole) evolution as a function of cosmic environment. Numerous state-of-the-art imaging campaigns at all wavelengths (X-ray to radio) are underway for the COSMOS field. I will briefly describe the overall COSMOS project with an particular emphasis on the ongoing long wavelength efforts, our 1.4 GHz observing campaign at the Very Large Array (VLA). It resulted in the deepest radio image at its resolution and areal coverage. First results of this large VLA project on the study of dusat-obscured star formation and evolution of AGNs are presented

Ionospheric calibration for long-baseline, low-frequency interferometry

Special Colloquium
Dr. James M. Anderson
ORATED
Joint Institute for VLBI in Europe

At frequencies below roughly 1 GHz, the ionosphere is often the main source of phase delay errors in radio interferometry. Self-calibration can remove this problem for strong sources, but imaging weak sources at low frequencies remains difficult for long-baseline interferometers. Correcting for the effects of the ionosphere is critical for the operation of LOFAR and similar instruments, especially on the longest baselines. I will review the basic features of the ionosphere as it affects radio astronomy and present results from efforts to calibrate current VLBI datasets with existing ionospheric calibration data, principally derived from Global Positioning System measurements. I will then discuss the current development of the Minimum Ionospheric Model (MIM) which is a promising method to enable the calibration of the ionosphere for instruments many hundred kilometers in size.

Multifrequency VLBA observations of 3C273 - evidence for magnetic jet launching models?

Special Colloquium
Dr. Tuomas Savolainen
ORATED
Tuorla Obs., Univ. of Turku, Finnland

Rapid, large amplitude flux density variations were serendipitously detected in the highly core-dominated radio-loud quasar 1156+295 while it was observed as a part of the MOJAVE survey programme at the VLBA on February 5, 2007. The observed variability in the correlated flux density at 15 GHz was as high as 40% in only 2.7 hours, and correlated variations were present on every baseline, which excluded the source structure as the cause of the variations. The antenna gains were carefully calibrated using 24 other sources observed in the experiment. This allowed us to construct an integrated flux density curve of the source as well as to study the changes in the shape of the visibility function during the IDV event. In this talk I will report these results as well as present an analysis of the observed variability in the context of interstellar scintillation. The observed variability timescale and the modulation index of 13% are consistent with refractive scattering by a nearby, highly turbulent screen. The large modulation index at 15 GHz implies, however, a scattering measure that is significantly higher than what is predicted by the models of Galactic distribution of free electrons.

The challenge of viewing the oldest light - Current and future observations of the Cosmic Microwave Background Radiation

Main Colloquium
Dr. Dorothea Samtleben
ORATED
Kavli Institute, Chicago University

The Cosmic Microwave Background Radiation stems from the very early Universe, only 400 kyears after the Big Bang, and represents a fruitful source of information about the content and development of the Universe. After its (accidental) discovery just four decades ago its frequency spectrum and intensity anisotropy have been measured in good detail most prominently by the satellite projects COBE and WMAP. The polarization anisotropy of the CMBR is significantly smaller than the intensity anisotropy so that it was only detected in recent years. One of the major goals of upcoming CMBR experiments is to reveal the very subtle signatures of inflation in the polarization pattern for which unprecedented sensitivity and control of systematics are mandatory. Since fundamental limits have been reached for the sensitivity of single receivers future experiments will take advantage of large receiver arrays in order to significantly increase the sensitivity. In this talk the challenge of future measurements and an overview of current and upcoming experiments will be presented. The talk will also focus in more detail on one of the ground-based efforts underway to study the polarization of the CMB, the Q/U Imagining ExperimenT (QUIET). QUIET is planning to use 91 (19) HEMT-based receivers in chip packages at 90 (40) GHz on a new telescope in the Atacama Desert in the next years and later expand to arrays of in total 1000 receivers.

Masers and Star Formation in Perseus Spiral Arm

Special Colloquium
Dr. Andrej Sobolev
ORATED
Astronomical Observatory, Ural State University, Ekaterinburg, Russia

On the example of a few well studied sources it will be described what do masers tell us about the objects in the regions of star formation. Advantages of observations of the objects from Perseus Spiral Arm will be described. Importance of the star formation research and pecularities of star formation in this galactic structure will be discussed.

The Dynamical Evolution of Ultraluminous Galaxies at Low and High Redshift

Main Colloquium
Dr. Linda Tacconi
ORATED
MPE Garching

In this talk I will review what we know about luminous merger evolution from high spatial and spectral resolution dynamical studies of the gas and stars. These results address the issues of merger induced starburst and AGN activity, whether (ultra)luminous mergers (ULIRGs) become elliptical galaxies, and possible evolutionary links between ultraluminous and QSO phases. I then compare the properties of local ULIRGs with those from recent spatially resolved dynamical studies of submillimeter galaxies at z 2.5.

Probing the early stages of low-mass star formation: from 10 pc to 100 AU scales

Special Colloquium
Dr. Jes Jorgensen
ORATED
CfA, Cambridge, USA

In the earliest evolutionary stages of young stellar objects, the central protostar is deeply embedded, surrounded by a large envelope of gas and dust. These objects emit large fractions of their radiation at far-infrared through submillimeter wavelengths. The typical mid-infrared fluxes of these sources are predicted to be very weak, but with the high sensitivity from the Spitzer Space Telescope it is now possible to observe the mid-infrared emission from the warm dust in their protostellar envelopes. Furthermore high angular resolution observations with the Submillimeter Array resolve the innermost regions of the envelopes and even the circumstellar disks. High excitation transitions of many common molecular species in the submillimeter likewise probe warm and dense gas in the envelope. In this talk I will present recent results from the ”Cores to Disk (c2d)” Spitzer legacy program and the ”Protostellar Submillimeter Array Campaign (PROSAC)” SMA key program concerning the deeply embedded stages of low-mass protostars. In particular, I will discuss how these observations constrain the star formation process - from the distribution of newly formed young stellar objects over parsec scales in molecular clouds to the physical and chemical structures of the inner 100 AU of their envelopes and disks.

On the bullet galaxy cluster and the law of gravity

Main Colloquium
Dr. Benoit Famaey
ORATED
Universite libre de Bruxelles

We present weak lensing observations of 1E0657-56, an extremely interesting object (z=0.3) in which the collisionless component and the fluid-like X-ray emitting plasma are spatially segregated due to the collision of two galaxy clusters. We fit this lensing map in a class of gravity theories interpolating between GR and MOND (General Relativity and Modified Newtonian Dynamics), so to infer the nature and amount of collisionless matter with less dependence on the validity of GR on cluster scales. We show that 1E0657-56 is dominated by a collisionless (most probably non-baryonic) component - in GR as well as in MOND. This result adds to the number of wrong MOND predictions based on observed baryons only (namely an inability in explaining dynamics of other X-ray emitting regions).

Non thermal processes in microquasar jets in high mass systems

Special Colloquium
Dr. Valenti Bosch-Ramon
ORATED
Max-Planck-Institut fuer Kernphysik, Heidelberg

High-mass microquasars, X-ray binaries with massive stellar companions and relativistic jets, are complex systems in which the jet is embedded within a very dense photon field. Moreover, the power of the wind could be of the same order than that of the jet. The long path, in Schwarzschild radii units, covered by the jet within the dense photon field and companion wind before leaving the binary system region (where star radiation and wind get weaker very fast) is likely to have important effects on the jet radiative processes. We compute the spectral energy distribution of the radiation produced in high mass microquasars with efficient particle acceleration in the their jets, and discuss briefly the impact of the wind on the jet evolution and radiative properties.

Quiet, please! - future protection of radio astronomy from interference

Special Colloquium
Dr. Roberto Ambrosini
ORATED
Istituto di Radioastronomia, INAF

As all users of radio telescopes know, the electromagnetic environment through which we try to detect very faint cosmic radio signals is not getting any cleaner. As part of our long-term strategy to enable the continued growth of radio astronomy, regulatory measures that limit the unwanted interference in our data play an important role. The saying ”Prevention is better than a cure” applies also to this situation - the less interference is legally allowed, the less we have to remove with RFI mitigation techniques. An overview will be given of the activities of radio astronomers worldwide in their fight in various regulatory arenas to keep our radio windows on the Universe clean. As a practical example, the work towards a Radio Quiet Zone for the giant Square Kilometre Array (SKA) radio telescope will be used. We will also describe how spectrum management for astronomy will be affected by new types of sources of interference (UWB devices), the new frequency market opened by the ”digital revolution”, the expectations of very efficient mitigation techniques, and by the increasingly strong will of the European Commission to control all management of the radio spectrum in Europe. CRAF is an Expert Committee of the European Science Foundation, and the common voice of radio astronomy across Europe for protecting our observational needs. This is quite an endeavour, because the actions to be taken are spread over all possible levels of interventions. The best strategy, in the long run, is a strong regulatory approach, shared by all EU nations and their national spectrum management Administrations, and finally applied to the local environment around each radio astronomy observatory. And, yes, please switch of your mobile phone during the talk...

The Expanded Very Large Array Project

Main Colloquium
Dr. Rick Perley
ORATED
NRAO, Socorro

The Very Large Array was completed in 1980, and has operated for twenty years with essentially no changes to the 1970s era technology on which is was based, other than some improved receivers and new frequency bands. By the 1990s, it was clear that incremental, individual improvements to the data transmission system, RF/IF electronics, and correlator would not be the optimal way to obtain significant improvements in the VLA’s scientific capabilities. Rather, a comprehensive plan to completely redesign the entire electronics and data processing system was the appropriate approach. The EVLA Project is the result of this comprehensive plan. The Project’s basic goals are to improve the technical capabilities of the VLA by a factor of ten in every major observational characteristic: Sensitivity, Frequency Coverage, Frequency Resolution, and Spatial Resolution, as well as to provide major improvements in Imaging Capabilities and Data Access. The EVLA Project is in fact a major upgrade of the world’s most productive and powerful radio telescope. It is a leveraged project, combining a sound existing array with the benefits of new technologies in signal transmission and data processing to provide fabulous new capabilities at a small fraction of the cost of an entirely new facility. In this talk, I will review the major specific goals of the project, its current progress and status, and anticipated timeline for availability new capabilities prior to its completion in 2012.

Dissecting blue compact dwarf galaxies

Special Colloquium
Dr. Polychronis Papaderos
ORATED
Universität Goettingen

In this talk I will review current ideas about the nature and starburst-driven evolution of blue compact dwarf (BCD) galaxies. This morphologically heterogeneous class of extragalactic objects provides an important nearby laboratory to study origin and implications of violent star-forming activity in gas-rich dwarf galaxies and to get insight into the process of dwarf galaxy formation and evolution in the early universe. Among other topics, I will focus on rare examples of extremely metal-deficient (12+log(mathrm{O}/mathrm{H})<7.6) BCDs presenting clear signatures of a young stellar population and extended ionized gas emission on a nearly galaxy-wide scale.

A Colloquium in Honour of Malcolm Walmsley's 65th Birthday

Special Colloquium
Multiple Speakers: Check abstract for details
ORATED


Speaker: Bonn - Cologne - Firenze: 35 Years of Molecular Astrophysics Program: 13:45 Getting together - Coffee 14:00 Karl Menten, MPIfR: Welcome & Introduction 14:30 Ed Churchwell, U of Wisconsin: Dirt, Really Big Molecules, and Bubbles 15:00 Jorma Harju, U of Helsinki: Glimpses into Dense Cores and the Early Stages of Star Formation 15:30 Coffee Break 16:00 Riccardo Cesaroni, Arcetri, Florence: IRAS20126+4104: the Never-ending Story 16:30 Mario Tafalla, OAN, Madrid: The Structure of Pre-stellar Cores: Infall, Depletion, and Malcolm 17:00 Reception Talks will be 20 minutes with 10 minutes set aside for ample discussions.

Dust and gas in protoplanetary disks

Main Colloquium
Dr. Carsten Dominik
ORATED
Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam

I will summarize the results of recent modelling of dust growth and settling in protoplanetary disks. For the first time now, such calculations have been coupled with full radiative transfer to show the observational effects of dust evolution in disks. These calculations show how dust coagulation leads to a fast depletion of small grains in the solar nebula, with severe consequences for the structure and appearance of the solar nebula. I will also show results of modelling the emission of the H2D+ molecule, a recently discovered tracer of cold gas and ionization in disks that may become an important tool in the future for tracing the gas component in protoplanetary disks.

Karl Friedrich Kuestner (1856-1936) -- Leben und Werk eines grossen Bonner Astronomen

Special Colloquium
Dr. Michael Geffert
ORATED
AIfA

Im August diesen Jahres jaehrt sich zum 150igsten Male der Geburtstag eines Astronomen, der vor 100 Jahren die Bonner Sternwarte leitete. Kuestner wurde als Sohn eines Maurermeisters in Goerlitz geboren und studierte in Berlin und Strasbourg. Er leitete 1882 die Expedition zur Beobachtung des Venusdurchgangs in Punta Arenas und entdeckte 1884 in Berlin die Polhoehenschwankungen. 1891 wurde Kuestner als Direktor der Sternwarte nach Bonn berufen, wo er 1899 den grossen Bonner Doppelrefraktor in Betrieb nahm. Kuestner galt als herausragender Beobachter, der mit groesster Sorgfalt arbeitete. Er beobachtete sowohl visuell am Meridiankreis als auch fotografisch am Bonner Doppelrefraktor. Die Platten, die er mit diesem Instrument aufgenommen hatte, waren von bestechender Qualitaet. Sie dienen bis heute zur Messung sehr genauer Eigenbewegungen von Sternen in Sternhaufen. Kuestner’s Arbeiten konzentrierten sich nach 1900 auch auf die sich rasch entwickelnde Spektroskopie. 1905 verueffentliche er eine originelle Arbeit zur Bestimmung der Astronomischen Einheit aus den Messungen der Radialgeschwindigkeit von Arktur. In dem Vortrag sollen Leben und Werk des Bonner Astronomen vorgestellt werden.

VLBI surveys for high accuarcy astrometry

Special Colloquium
Dr. Loenid Petrov
ORATED
NASA Goddard, USA

The VLBI method allows us to determine coordinates of compact radio sources with accuracy at 1 nanoradian level using methods of absolute astrometry. During the 21st century the number of sources with precise position determined with VLBI using absolute astrometry increased by a factor of 5. Technology of running big astrometric surveys is discussed. Recent results and their impact on various applications are shown.

Magnetic Fields in the Formation of Low Mass Stars: The observational perspective

Main Colloquium
Dr. Josep Miquel Girart
ORATED
CSIC-IEEC, Bellaterra, Spain

Is the star formation controlled by ambipolar-diffusion or by turbulence? Despite the major advances in the knowledge of the star formation, this question still generates a vivid debate. The studies of the magnetic fields properties in molecular clouds are important to test the ambipolar-diffusion scenario. In this talk, I will review the status of the observations of magnetic fields in molecular clouds. I will also present the results of the high angular resolution observations of polarized dust emission carried out with the Submillimeter Array toward NGC 1333 IRAS 4A, a low mass binary protostellar system. The observed magnetic field morphology is in agreement with the ambipolar-diffusion models of the formation of low-mass stars in magnetized molecular clouds at the scales of hew hundreds AU. The magnetic field in this region is more important than turbulence in the evolution of the system. We also find a misalignment between the magnetic and spin axes, which may have been important in the formation of the binary system.

Looking into the heart of a core collapse supernova

Special Colloquium
Dr. Ewald Müller
ORATED
MPA Garching

Core collapse supernovae are dramatic explosions of massive giant stars. Thus, the optical outburst begins only hours after the actual onset of the catastrophe in the very center of the star. There the burnt out stellar iron core collapses in a fraction of a second to a neutron star thereby liberating the energy which causes the supernova explosion. The only means to get direct and immediate information about the supernova “engine” is from observations of neutrinos emitted by the forming neutron star, and through observations of gravitational waves which are generated when the flow or the neutrino flux are not perfectly symmetric. Numerical simulations provide a third possible route to look into the heart of a core collapse supernova. However, they pose a true challenge as they require multidimensional neutrino radiation hydrodynamics, a detailed treatment of weak interaction processes and neutrino matter coupling, the handling of vastly different length and time scales, in particular when simulating shock propagation through the envelope of the progenitor star, and possibly the incorporation of effects due to rotation and magnetic fields. In the talk the methodology and some recent results of such core collapse supernova simulations will be discussed.

Periodic variations in 6.7 GHz methanol masers

Special Colloquium
Dr. Sharmila Goedhart
ORATED
Hartebeesthoek Radio Astronomy Observatory, South Africa

An intensive monitoring program of 54 6.7-GHz methanol maser sources was carried out at the Hartebeesthoek Radio Astronomy Observatory from January 1999 to April 2003. The monitoring program was subsequently continued on 19 sources of interest. Analysis of the resulting time-series stretching over seven years shows that six of the sources are periodic, with periods ranging from 133 days to 505 days. The waveforms range from sinusoidal to sharp flares and there can be other long term trends in the time-series. The amplitudes of the variations can also change from cycle to cycle. Explaining the variations is a challenge because of the complexity of the circumstellar environment, and the wide range of variability behaviour seen. I will present the periodic masers, and discuss the possible causes of the variability.

The Mopra G333 Multi-wavelength Survey: Investigating Massive Star Formation in the Southern Galactic Plane

Main Colloquium
Dr. Maria Cunningham
ORATED
University of New South Wales, Sydney, Australia

The G333 project is a multi-wavelength survey aiming to put together a comprehensive picture of massive star formation throughout an entire giant molecular cloud complex. The aim of the project is to to answer observationally some of the key questions about the dynamical processes surrounding massive star formation (e.g. massive stellar winds and large-scale galactic flows) and their relative importance in regulating the star formation process. We are using the new broadband capabilities of the Mopra telescope to map the distribution of around 20 different molecules in an approximately 1 degree square region of the southern Galactic plane (the G333.6-0.2 giant molecular cloud complex). The multi-molecular line nature of this survey is what distinguishes it from similar surveys, and is crucial for gaining a clear picture of the energetics and dynamics of the gas. Different molecular transitions trace different regions of gas in terms of density and excitation, and so can be used to follow energy transfer through the molecular cloud complex. Investigating and understanding the chemistry of this region is a necessary part of this project if the molecular line observations are to be correctly interpreted, and is an interesting goal in itself. In addition to the molecular line observations we are observing continuum emission at sub-millimetre and centimetre wavelengths, and radio-recombination lines. These observations will then be combined with existing infrared and atomic hydrogen data to put together a comprehensive picture of massive star formation, and its relationship to the chemistry and dynamics of the entire cloud complex.

The formation and evolution of elliptical galaxies

Main Colloquium
Dr. Thorsten Naab
ORATED
University Observatory Munich

Gas rich mergers of spiral galaxies might evolve into elliptical galaxies. We show that the kinematic properties of simulated merger remnants including the effect of gas are in good agremment with nearby merger remnants and, after 4-6 Gyrs, with low mass elliptical galaxies. However, the properties of massive ellipticals can not be reproduced. In combination with theoretical evidence from stellar populations we argue that mergers of disk galaxies are a viable but not the dominant formation mechanism for elliptical galaxies. Possible formation histories in the cosmological context are discussed.

Understanding Depolarisation Canals in the Southern Galactic Plane

Special Colloquium
Katherine Newton-McGee
ORATED
Sydney University

Measurements of the Galactic radio polarized background have revealed many complicated structures in the interstellar medium (ISM). Recently there has been an interest in the dark and narrow depolarization canals. I will present a study of a test region in the southern Galactic Plane taken with the Australian Telescope Compact Array (ATCA). ATCA is a radio synthesis telescope and these three regions were taken using a mosaicking technique at a range of frequencies around 1.4 and 1.7 GHz, at two different angular resolutions. At these frequencies the canals are ubiquitous in regions of strong polarization. The range of frequencies and resolutions combined with statistical analysis of the relevant Stokes parameters and position angle maps have led us to conclude that at these frequencies the majority of the canals are caused by differential Faraday rotation. It will be these canals that we are focusing on, rather than those caused by beam depolarization. We discuss the evidence that canals are contours following nulls in differential Faraday rotation by presenting rotation measure maps and analysis of the angular separation of the canals. We also present a new way a potentially new method of studying polarisation canals.

ATLAS - A very deep look into the southern radio sky

Main Colloquium
Enno Middelberg
ORATED
MPIfR

Over the last two years, we have conducted the Australia Telescope Large Area Survey (ATLAS) of two regions in the southern sky at 1.4 GHz. The aim is to produce an extremely wide (6 square degrees) deep (10-15 uJy rms) radio survey with the Australia Telescope Compact Array. The areas were chosen to cover fields which have deep optical, near-infrared, far-infrared, and in some parts, deep X-ray data, so that this project may be the most comprehensive multi-wavelength survey yet attempted. We are now 50% through the radio observations, which I describe along with the challenges in reaching the desired dynamic range, the source extraction and the cross-identification with IR/optical observations, and the first intriguing results. We have used stacked radio images to statistically detect sources below the actual image rms, to prove that the radio-infrared relation holds to uJy levels. We also have detected a new rare class of objects, the Infrared-Faint Radio Sources (IFRS), which are relatively strong radio sources with no infrared counterparts.

High-frequency Carbon Recombination Line as a Probe to Study the Environment of Ultra-compact HII regions

Special Colloquium
Dr. Anish Roshi
ORATED
Raman Research Institute, Bangalore, India

A recent Arecibo survey of carbon recombination lines (CRLs) near 9 GHz toward Ultra-compact HII (UCHII) regions have detected lines toward a majority (11 out of 17 sources; 65% detection rate) of the selected sources. Further high-resolution observations made with the VLA (Very Large Array) toward two UCHII regions – W48A and W49-North – show that the CRLs are detected against the bright continuum emission from the UCHII regions. The detection against the continuum emission suggests that the regions responsible for CRL emission are associated with UCHII regions. CRL emission originates from photo-dissociation regions (PDRs) formed at the interface between the HII regions and the dense (>10^5 cm-3) natal molecular clouds harbouring them. The far-ultraviolet (6 to 13.6 eV) photons from OB stars embedded in the UCHII regions produce these PDRs where carbon will be ionised. We have developed non-LTE models for the CRL emission observed toward a subset of UCHII regions selected from the Arecibo survey and VLA observations. In particular, detailed modelling has been done toward W48A were both multi-frequency (5, 8, 14 & 42 GHz) and high-resolution data were available. In this modelling, the temperature, electron and carbon ion density profiles as a function of depth into the PDR from the surface of UCHII region were taken from one-dimensional PDR model of Le Bourlot et al. (1993). Our studies show that a multi-frequency, high-resolution CRL data set can be use to : (1) estimate the physical properties of the PDR material; (2) study the kinematics of the PDR material relative to the HII region gas and (3) constrain the magnetic fields in the vicinity of UCHII regions. We further show that the derived properties of the environment and HII region as well as their kinematics can be used to address the lifetime problem of UCHII regions by investigating whether the HII regions are confined in the natal cloud.

Magnetars and Their Environments

Main Colloquium
Dr. Bryan Gaensler
ORATED
Sydney University

The last decade has revealed remarkable diversity in the neutron star population. Most notable amongst these new discoveries is the emergence of a population of ”magnetars”, neutron stars whose radiation is powered by extreme magnetic fields, in excess of 1015 gauss. While there have been many intensive observations of magnetars themselves, vital clues as the nature of these exotic objects can come from understanding their interactions with their environments. I will present several recent studies which illustrate this point, focusing on the identification of wind bubbles and star clusters around several magnetars, along with on-going observations of SGR 1806-20, which for a fraction of a second in 2004 outshone the entire Milky Way by a factor of a thousand. These observations provide crucial new information on the physics and demographics of these extreme objects.

The Allen Telescope Array

Special Colloquium
Dr. David DeBoer
ORATED
Seti Institute, USA

The Allen Telescope Array is a new interferometer being built at the University of California Berkeley’s Hat Creek Radio Observatory in northern California. It is a joint project between the SETI Institute of Mountain View, CA, and the Radio Astronomy Laboratory at the University of California Berkeley and has been primarily funded to-date by the Paul G. Allen Charitable Foundations of Seattle, WA. The array is comprised of many 6.1 meter offset Gregorian dishes with ultrawideband (0.5-11.2 GHz) feeds. The first 42 elements of the array are coming on-line this year, with an eventual goal of 350 elements. The small dishes and wide-bandwidths allow very flexible observing modes, whereby multiple users can productively and independently use the entire array simultaneously–primarily to conduct large surveys done concurrently by the Radio Astronomy Lab and the SETI Institute. This talk will provide an introduction and overview of the Allen Telescope Array.

The State and Evolution of Isolated Dense Molecular Cores

Special Colloquium
Dr. Jens Kauffmann
ORATED
MPIfR

I will present highlights from my recent work on nearby (le 500 ~ m pc) isolated dense molecular cores, the sites of low-mass star formation. The sample includes starless and protostellar cores and allows to compare their properties in a homogenous manner. One aim of the research is to understand how the mass distribution in dense cores controls the presence or absence of forming stars. A detailed analysis reveals conditions that are necessary (but not sufficient) for active star formation to be possible. Class 0 and class I protostars covered by my surveys cannot be uniquely discriminated, suggesting a revision of criteria used to assign infrared classes. Furthermore, I report the discovery of L1148-IRS, a candidate Very Low Luminosity Object (VeLLO; L le 0.1 , L_{odot}) in the L1148 dense core. The global spectral energy distribution, the morphology at approx 1 ~ m mu m wavelength, the inferred density profile, and the tentative detection of inward motions towards L1148-IRS are consistent with the source being an embedded protostar. If L1148-IRS is indeed a VeLLO, then it is an interesting one. First, the final mass would be significantly subsolar (le 0.25 , M_{odot}). Second, the formation of L1148-IRS could not be understood in the framework of quasistatic evolution of dense cores.

Ammonia in the Local (and not so Local) Universe

Main Colloquium
Dr. Jürgen Ott
ORATED
ATNF, Australia

The transitions of ammonia, the most abundant top-heavy molecule, can be utilized as an easy-to-use thermometer for molecular gas. Over the last few years, a new generation of 1cm receivers at ATNF and other telescopes has been commissioned which enables astronomers to exploit this peculiar feature in far more objects than before. I will present results from extensive ammonia observations toward the Galactic Center, nearby starburst galaxies, and ULIRGS.

Heating of Clusters of Galaxies by Outbursts from a Central Active Galaxy

Special Colloquium
Dr. Paul Nulsen
ORATED
CfA, Cambridge, USA

TBA

AGN in Low Surface Brightness Galaxies

Main Colloquium
Dr. Mousumi Das
ORATED
Raman Research Institute, Bangalore, India

Low Surface Brightness (LSB) galaxies represent a very extreme population on the Hubble Sequence. Morphologically they are similar to late type spirals but are much more metal poor indicating that they have a low rate of star formation compared to bright galaxies. Even though they have massive HI gas disks, their stellar disks are diffuse and they are dark matter dominated even in their inner disk. The dark halo and their relative isolation compared to other spirals may have led to a slower rate of evolution compared to other bright spirals on the Hubble Sequence. Although AGNs are ususally associated with bright spiral galaxies, many have been found to show AGN activity both in the optical and radio domain. This raises many interesting questions about the formation and evolution of AGN in spiral galaxies. In this talk, multiwavelength observations of LSB galaxies will be presented and the implications of these results with respect to AGN and galaxy evolution will be discussed.

Compact radio structure in AGN

Main Colloquium
Dr. Yuri Kovalev
ORATED
NRAO Green Bank & Lebedev Physical Institute, Moscow

We discuss the compact radio structure in 250 bright flat-spectrum extragalactic radio sources using interferometric fringe visibilities obtained with the VLBA in the 2 cm VLBA / MOJAVE project. With projected baselines out to 440 million wavelengths, we are able to investigate source structure on typical angular scales as small as 0.05 mas. In the second half of the talk we present the current status of the VLBA search for compact extragalactic sources at 13/3.6 cm. An efficiency of the search was significantly improved since a new method to predict VLBI compact emission was applied. The method is based on an analysis of continuum spectra provided by our survey at RATAN-600.

The High Energy Intergalactic Medium: New Probes and Techniques

Special Colloquium
Prof. Philipp Kronberg
ORATED
University of Toronto, Canada

I describe new attempts to detect diffuse IGM radio emission on degree-scales. Separately, I describe the first attempts to directly detect Faraday rotation in cosmological large scale structure at low z, and compare both results with “astrophysical expectation”. If time permits I will comment on potential future implications of these experimental low-level radiometry experiments, both instrumental and astrophysical.

The Low Frequency Demonstrator (and other low frequency arrays)

Special Colloquium
Dr. Bob Sault
ORATED
ATNF, CSIRO, Sydney, Australia

After the demise of the original LOFAR consortium, three low frequency radio synthesis array designs have risen from the ashes - LOFAR, the LFD and the LWA. The three have broadly similar basic designs, and have overlapping science goals. This talk briefly reviews the different designs. It then goes on to consider the Low Frequency Demonstrator in more detail. This is a member of the new breed of “large N small D” array designs which relies on many simple antenna elements, inexpensive digital hardware and greater reliance on calibration and imaging algorithms. Some of the novel aspects of the telescope are considered.

Field of Streams: dissecting the Galactic halo

Main Colloquium
Dr. Simon Vidrih
ORATED
Cambridge, UK

Digital Sky Survey (SDSS) Data Release 5 (DR5) u, g, r, i, z photometry is used to study Milky Way halo substructure in the area around the North Galactic Cap. A simple color cut (g-r < 0.4) reveals the tidal stream of the Sagittarius dwarf spheroidal, as well as a number of other (new) stellar structures in the field (Monoceros ring, Virgo overdensity, Orphan stream, dwarf satellites in Canes Venatici, Bootes and Ursa Major). Two branches of the Sagittarius stream are clearly visible in an RGB-composite image and there is also evidence for a still more distant wrap behind one of the branches. A comparison of these data with numerical models suggests that the shape of the Galactic dark halo is close to spherical.

Water megamasers in NGC4258: Monitoring a nuclear accretion disk with the 100-m telescope at Effelsberg for more than 11 years

Special Colloquium
Bettina Roselt
ORATED
MPIfR Bonn

TBA

Comets at radio wavelengths

Main Colloquium
Dr. Dominique Bockelée-Morvan
ORATED
LESIA, Observatoire de Paris

The radio domain, from centimetric to submillimetric wavelengths, is a powerful tool to study the molecular and isotopic composition of cometary atmospheres, and characterize a number of processes that lead to its development and physical properties. About 20 molecules have been identified using millimeter/submillimeter spectroscopy. Their nature and relative abundances show striking similarities with star-forming regions. A few isotopic ratios have been measured, including D/H ratios, and suggest that presolar material underwent significant processing in the Solar Nebula before incorporation into pre-cometary ices. About 30 comets have now been observed by millimeter spectroscopy. They show a strong diversity in composition, which origin is unclear and seems not correlated with their dynamical origin, Oort cloud or Kuiper Belt. The extraordinary activity of comet Hale-Bopp allowed us to perform unique interferometric observations with the IRAM Plateau de Bure interferometer. The constraints obtained on the radial distribution and origin of several species in the coma and the observation of CO rotating jets prefigure the cometary science that will be accomplished with ALMA. Finally, I will present our ongoing investigation of H_2O, H_2^{18} and NH_3 using the Odin satellite, in preparation to future Herschel observations.

Dynamics of Intermediate Mass Black Holes in Star Clusters and Galactic Nuclei

Main Colloquium
Dr. Holger Baumgardt
ORATED
AIfA

X-ray observations of starburst and interacting galaxies have revealed a class of ultra-luminous X-ray sources (ULX), whose luminosities exceed the Eddington luminosities of stellar mass black holes by orders of magnitude, making them good candidates for intermediate mass black holes (IMBHs). If real, IMBHs would provide an important link between the supermassive black holes in galactic centres and ”normal” stellar mass black holes. I will present results of N-body simulations of the dynamical evolution of young star clusters. Conditions under which run-away merging of stars can lead to the growth of intermediate-mass black holes are illustrated for low and high mass clusters. I will then show how clusters containing IMBHs evolve at later times and discuss chances of finding them in the Milky Way. I will also discuss whether the recently found hyper-velocity stars in the galactic halo are compatible with being ejected by an inspiraling IMBH in the galactic centre.

A Quasi-Periodic Modulation of the Radio Light Curve of the Blazar PKS B0048-097

Special Colloquium
Matthias Kadler
ORATED
RAIUB & MPIfR

Multi-frequency monitoring observations of blazars exhibiting quasi-periodic oscillations (QPO) may allow the putative inter-relation between the compact radio jet and the broadband spectral energy distribution to be deciphered. Attempts have been made to understand such periodic behavior as a result of orbital motion of two black holes in a binary system, helical jet structures, shocks, and instabilities of the disk or jet-plasma flow, but the long time scales involved often limit testing of such models. In this talk, I will report on the detection of a particularly strong, and persistent quasi-periodic long-term modulation of the compact-jet emission of the BL Lac object PKS B0048-097, with a period varying between 350 and 600days. Moreover, lambda2cm VLBI imaging shows dramatic changes of the position angle of the parsec-scale jet, that may be related to the QPO behavior. The large amplitude of the variability and the pronounced structural variability make PKS B0048-097 a promising target for future multi-frequency monitoring campaigns to decipher the blazar-variability phenomenon.

High Resolution Study of Selected Intraday Variable Sources

Special Colloquium
Krisztina Gabanyi
ORATED
MPIfR Bonn

20-25% of flat spectrum extragalactic radio sources exhibit Intraday Variability (IDV), which is thought to be at least partly due to interstellar scintillation. The theory of refractive interstellar scintillation (RISS) provides explanations for a number of the observed variability characteristics. However, some difficulties remain. In this talk, I concentrate on different observational approaches to study the IDV phenomenon. Short time-scale variations of the flux-density of flat spectrum extragalactic radio sources were measured towards two regions to compare lines of sight passing through very different amounts of interstellar matter. The results are consistent with the hypothesis that the interstellar material responsible for IDV is at a distance of less than 100 pc. In addition, I present various (total and polarized intensity, single dish and VLBI) observations of selected IDV sources and discuss the applicability of RISS. Finally, I discuss the derived characteristics of the turbulences in the ISM.

Massive star-forming regions at high-spatial resolution

Main Colloquium
Dr. Henrik Beuther
ORATED
MPIA, Heidelberg

High-mass star formation is known to proceed in a clustered mode at on average large distances. Since the earliest evolutionary stages are deeply embedded in their natal dust and gas cores, interferometric observations from cm to submm wavelengths are the most promising tools to investigate the processes taking place during the birth of high-mass stars. I will present recent interferometric studies with the SMA, PdBI, and ATCA of very young massive star-forming regions disentangling their physical and chemical properties. Discussed topics will be the onset of massive star formation, the chemical complexity of Hot Molecular Cores, potential massive accretion disks and the origin of the IMF.

High-energy Activity at the Galactic Center

Main Colloquium
Prof. Fulvio Melia
ORATED
University of Arizona

Once hidden almost completely by the intervening gas and dust along our line-of-sight, the Milky Way’s central black hole first manifested itself as a radio point source, then as a variable infrared object and, most recently, as a dynamic emitter of X-rays. There are even indications that it may be the dominant accelerator of relativistic protons, accounting for the central (HESS) TeV source and, possibly, the diffuse TeV emission associated with molecular clouds along the Galactic plane. In this talk, we will discuss work in progress to understand what this high-energy activity is revealing about the environment within tens of Schwarzschild radii of the central supermassive object.

Numerical simulations of blazar jets and their non-thermal radiation

Special Colloquium
Dr. Petar Mimica
ORATED
University of Valencia, Spain, Spain

Blazars are a class of AGN which exhibit a rapid variability at radio, infrared, visual and X-ray wavelengths. They are characterized by a non-thermal spectral continuum and a strong and rapidly varying polarization. Probable cause of the variability are collisions of the parts of the inner jet moving at different velocities, while the jet is oriented close to the line of sight. Results of relativistic hydrodynamic (RHD) and relativistic magnetohydrodynamic (RMHD) simulations of collisions of dense shells within blazar jets are presented, as well as the synthetic light curves resulting from them. Basic characteristics of the dynamics and the efficiencies of two-shell collisions are shown, the influence of the initial shell properties and the resulting light curves is studied, and an analytic model is outlined, which aids in interpreting the observed blazar flares.

The influence of gravitational microlensing on spectra of lensed QSOs

Special Colloquium
Dr. Luka Popovic
ORATED
Astronomical Observatory, Belgrade, Serbia

Gravitational lensing is in general achromatic, however, the wavelength-dependent geometry of the different emission regions of lensed quasars may result in chromatic effects. Since sizes of the emitting regions are wavelength-dependent, microlensing by stars in the lens galaxy will lead to a wavelength-dependent magnification. This can be used in the investigation of the size and geometry of QSO emission regions. Here we will discuss the influence of gravitational microlensing on the spectra of lensed quasars, and possible usage of this to investigate the innermost part of quasars. Moreover, to investigate the variability of lines and X-ray/UV/optical continuum caused by microlensing, we studied the effects of microlensing on quasar spectra produced by the crossing of a microlensing pattern across a standard relativistic accretion disk. To describe the disk emission we used a ray tracing method considering both metrics, Schwarzschild and Kerr. We found that the Fe Kalpha and X-ray continuum may experience more significant amplification by a microlensing event (even for microlenses of very small mass) than the UV/optical lines and continuum. We conclude that gravitational microlensing can be a very useful tool for investigation of the unresolved central part of lensed QSOs (X-ray region, continuum source and broad line region).

Detection of radio pulses from cosmic ray air showers with LOPES

Special Colloquium
Andreas Horneffer
ORATED
MPIfR Bonn / Radboud University Nijmegen

The earth’s atmosphere is continuously bombarded by high energy particles, called cosmic rays. Even 90 years after their discovery the origin and acceleration of the highest energy particles is still unknown. Measuring their energy, mass, and arrival direction is the most promising way to solve their mystery. Air showers induced by cosmic rays are known to emit radio pulses since these pulses were detected in 1965. In the 1970ties the measurement of these radio pulses ceased almost completely mostly due to difficulties with radio interference. The advent of fast digital computers and high bandwidth, high dynamic range ADCs enables us to store the whole waveform information of a radio pulse in digital form. Being a fully digital radio telescope LOFAR can take advantage of this and will thus be able to measure radio emission from air showers. We have built LOPES a LOFAR Prototype Station set up at the site of KASCADE-Grande an existing air shower array. We use a prototype of the LOFAR electronics sampling the whole radio signal in the frequency band of 40-80 MHz. Recording the whole waveform information, we can supress narrow band radio interference by filtering in frequency space and pulsed interference by digital beam forming. We can also use the results from KASCADE-Grande as starting points for our analysis. With this LOPES is able to reliably measure radio pulses from air showers. The data from January till September 2004 has been analysed in conjunction with air shower parameters from the KASCADE array. In 228 out of 412 selected events a radio pulse from the air shower was found. We found clear correlations between the height of the radio pulse and the shower size and the angle to the geomagnetic field. The latter correlation supports the theory that the air shower emission is synchrotron radiation in the geomagnetic field.

Spektroskopie mit dem PEPSI-Instrument des LBT

Special Colloquium
Prof. Klaus G. Strassmeier
ORATED
Astrophysical Institute Potsdam

TBA

Gas accretion and outflows in early-type and radio galaxies

Main Colloquium
Dr. Raffaella Morganti
ORATED
ASTRON

I will present recent results on the study of neutral hydrogen around early-type and radio galaxies. We have used the large-scale (tens of kpc) HI emission - in combination with information on the stellar population and ionised gas of the host galaxy - to find clues on the origin and evolution of these objects. On the nuclear (kpc) scale, fast ( 1000km/s) outflows of neutral gas (from 21-cm HI absorption) have been observed and studied in strong radio sources. The outflows likely originate from the interactions between radio jets and the gaseous medium and have mass outflow rates comparable to starburst-driven superwinds. The impact on the evolution of the host galaxies will be discussed.

The Cornell-Caltech Atacama Telescope project

Special Colloquium
Multiple Speakers: Check abstract for details
ORATED


Speaker: R. Giovanelli, T. Sebring, and J. Zmuidzinas Cornell University and the California Institute of Technology have entered a partnership to build a 25m class far infrared/submm telescope, CCAT. The telescope will be located at very high altitude (ca. 5600 m) in the Atacama desert of northern Chile. First light is targeted for 2012. Principal science goals include the survey of the epoch of galaxy formation, the investigation of star and planet origins and of the outer regions of the Solar System. The project is designed to optimize operational synergies with ALMA, as well as to accomodate the rapidly moving technology wave of large format bolometer arrays. The presentation will focus principally on the technical aspects of the project.

The Evolution of Massive Galaxies

Main Colloquium
Prof. Hans-Walter Rix
ORATED
MPIA, Heidelberg

Most massive galaxies at the present epoch are spheroidal, have almost exclusively old stars and have usually dormant massive black holes at their center. Recent deep imaging and redshift surveys now allow to address directly when most stars formed in these galaxies, when and why star-formation ceased int the massive objects and when they obtained the current dynamical configuration. I will report on recent results from our ground- and space-based surveys.

Cosmic Reionization: Theory and Observations

Special Colloquium
Dr. Benedetta Ciardi
ORATED
MPA, Garching

With the advent in the near future of radio telescopes as LOFAR, a new window on the high-redshift universe will be opened. In particular, it will be possible, for the first time, to observe the 21cm signal from the diffuse Intergalactic Medium (IGM) prior to its reionization and thus probe the “dark ages”. In this talk I will present results of simulations of IGM reionization, based on a combination of high resolution N-body simulations (to describe the dark matter and diffuse gas component), a semi-analytic model of galaxy formation (to track the evolution of the sources of ionizing radiation) and the radiative transfer code CRASH (to accurately follow the propagation of ionizing photons into the IGM). In addition I will discuss the observability of the 21cm signal from the diffuse IGM, expected in the simulated reionization histories.

Quantum Mechanical Aspects of Astrochemistry

Main Colloquium
Prof. Stephan Schlemmer
ORATED
Universität zu Köln

A large number of astrophysically observed molecules point at a rich chemistry in the interstellar medium (ISM), even in cold molecular clouds. Experiments in trap apparatus demonstrate that ion molecule reaction play an essential role. Selected examples are used in this presentation to show that at the low temperatures of the ISM simple quantum mechanical aspects like zero point energy, tunnelling, and the conservation of nuclear spin are of crucial importance. Because of these reasons, e.g. deuterated molecules are enriched up to twelve orders of magnitude. Many of those phenomena are not fully explained to date. Laser experiments like those at the free electron laser, FELIX, shall help to solve the mysteries.

Cosmological Applications of the XMM-LSS Cluster Sample

Special Colloquium
Dr. Florian Pacaud
ORATED
AIfA

The XMM-LSS is a legacy XMM Large Program that is using the unprecedented sensitivity and the large field of view of XMM to map the large scale structures of the Universe. The survey follows the distribution of galaxy cluster out to zsim1 and X-ray emitting AGNs to zsim4. The region observed by XMM-LSS is of special interest due to the wealth of data available at this location, including UV (GALEX), optical (CFHTLS), IR (SWIRE), radio (VLA) and will be observed by the APEX SZ survey in 2006. These different wavelength windows allow us to study the astrophysics of the region in distinct and complimentary ways. In my presentation I will describe the construction of the XMM-LSS cluster sample: from the X-ray photon lists to the spectroscopic identification and validation of cluster candidates. With roughly 70 confirmed clusters, this represents the largest deep cluster sample to date over a single region (5 square degrees) and unveils - for the first time - groups out to a redshift of 0.5. The sample also contains a number of clusters above z>1. I will then review the physical properties of detected clusters and their redshift distribution, which are in turn compared with the predictions of the concordance model of cosmology. Finally I will discuss future prospects for the use of the multi-wavelength dataset to diminish the degeneracy between cosmological information and cluster physics.

A multi-wavelength study of highly episodic stellar mass loss on the AGB

Main Colloquium
Prof. Hans Olofsson
ORATED
Onsala Space Observatory, Sweden

Mass loss from the surface is the most important phenomenon for the final evolution of low- and intermediate-mass (0.8-8 Msun) stars on the asymptotic giant branch (AGB). Its existence is well established, its characteristics is reasonably well established, while the mechanism behind it remains uncertain. The mass loss is believed to start early on the AGB at a low rate, and then gradually increase to reach values of 1e-4 Msun/yr at the end (at least for the more massive stars). A two-stage process, the radial pulsation of the star combined with radiation pressure on grains formed in the upper atmosphere, is believed to be the mechanism behind the mass loss. Since these stars produce a large number of elements, through nuclear burning and the s-process, that are convectively brought to the surface of the star, the mass loss is also important for the chemical evolution of galaxies. In this presentation a phase of highly episodic mass loss, rate changes by more than two orders of magnitude during a few hundred years, is discussed in terms of multi-wavelength observations and numerical models of the emission.

Discrepant image flux-density ratios in the gravitational lens JVAS B0218+357: A multi-frequency and phase-reference VLBI invest

Special Colloquium
Rupal Mittal
ORATED
MPIfR, Bonn

Active galactic nuclei at the center of galaxy clusters with gas cooling times that are much shorter than the Hubble time have emerged as heating agents powerful enough to prevent further cooling of the intracluster medium (ICM). We have carried out an intensive study of the AGN heating-ICM cooling interrelation by comparing various cluster parameters of the HIFLUGCS sample to the integrated radio luminosity of the central AGN, L_{ extrm R}. Adopting the central cooling time, t_{ extrm cool}, as the diagnostic to ascertain cooling properties of the clusters, we find there is a strong dependence of the presence of a cluster center radio source on the cooling time, such that shorter the cooling time, more likely it is for a cluster to host a central radio source. Similarly, we find that L_{ extrm R} in clusters with very short cooling times depends strongly on the cluster scale. In my talk, I will give a brief overview of the cooling problem in galaxy clusters and our current understanding of the vital role played by AGN heating in clusters where cooling is most severe.

Harmonizing Lambda CDM and Observations: Near-Field Cosmology with Dwarf Galaxies

Special Colloquium
Dr. Helmut Jerjen
ORATED
Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Australia

The epoch of the galaxy formation must leave an imprint in the properties of the mass function of collapsed objects and in its observational manifestation the luminosity function. At present the faint end of the luminosity function of galaxies is poorly understood. I will discuss how technical and methodical developments over the last few years provide the capability to identify dwarf galaxy candidates and to measure distances to very faint levels which will lead to accurate knowledge of the luminosity function over the full range of galaxy clustering scales. This will provide crucial input to constrain both the initial cosmological conditions and the modulating astrophysical processes.

The Motion of the Earth in its Surroundings

Special Colloquium
Prof. G.A. Tammann
ORATED
University of Basel

TBA

How bright is the universe?

Special Colloquium
Prof. Dr. Stefan Wagner
ORATED
Landessternwarte Heidelberg

TBA

The role of disks in O-B star formation

Main Colloquium
Dr. Riccardo Cesaroni
ORATED
Osservatorio Astrofisico di Arcetri, Italy

Notwithstanding the great progress made in the last decade, the formation of high-mass stars remains to be properly understood. The term “high-mass” is commonly used to indicate OB-type stars with luminosities above a few 1000 Lsun. For these, radiation pressure should halt the infall of circumstellar material and hence prevent further growth of the stellar mass. Consequently, it is not obvious that stars in excess of 6-8 Msun can form through accretion as well as low-mass stars. Recent observations and theoretical studies have begun to shed light on this intriguing topic. After a general introduction to the problem of star formation, I will discuss the most relevant findings obtained by us and the role these may play in discriminating between different models of OB star formation. In particular, after illustrating the detection of accretion disks and disk-like structures rotating about high-mass (proto)stars, I will show how this result supports the (non obvious) idea that B-type stars can form through a mechanism similar to that of low-mass stars. The formation of early O-type stars remains instead an open issue, which might involve more “exotic” scenarios.

Formation and evolution of the Large and Small Magellanic Clouds

Special Colloquium
Dr. Kenji Bekki
ORATED
University of New South Wales, Sydney, Australia

We discuss the origin of physical properties of the LMC and the SMC by comparing recent observational results of the Clouds and our numerical simulations. We particularly discuss (1) formation of asymmetric HI gas in the LMC, (2) the origin of the Magellanic Bridge, (3) the long-term evolution of the LMC’s stellar disk, (4) the origin of the “age-gap” in the LMC’s globular cluster system, and (5) the SMC’s stellar populations in the context of the Galaxy-LMC-SMC interaction.

Cosmology with the Spatial Distribution of Galaxies and Clusters of Galaxies

Main Colloquium
Dr. Peter Schuecker
ORATED
MPE, Garching

Galaxies and clusters of galaxies trace the spatial distribution of cosmic matter up to Gigaparsec scales. They are thus used for many cosmological investigations. Traditionally, the tests are based on the cold dark matter (CDM) paradigm of cosmic structure formation. Here, the systematic errors are mainly determined by the calibration of the mass-observable relations (e.g. mass-luminosity and galaxy biasing). New cosmological tests are presently developed which try to circumvent the CDM and mass-observable assumptions by measuring the baryonic acoustic oscillations (BAOs) in the large-scale distribution of galaxies and clusters of galaxies. The formation of the BAOs is governed by very simple physics which leads to the hope for a new almost ‘assumption-free’ and thus quite robust type of cosmological test. Such tests are of considerable importance, especially in the light of the determination of the equation of state of the dark energy. The talk summarizes recent results of cosmological tests based on the spatial distribution of galaxies and clusters of galaxies, and describes future experiments based on BAOs.

Cepheids, supernovae Ia and the Hubble constant

Main Colloquium
Prof. G.A. Tammann
ORATED
University of Basel

The Cepheid Period-Luminosity Relation is not universal. It is significantly different in our Galaxy and the LMC. This can be attributed to metallicity differences. Hence, Cepheid distances can be corrected for metallicity differences of the objects. 10 corrected distances from SNe Ia host galaxies lead a very uniform luminosity of the SNe, which can be applied to SNeIa up to 30000 km/s. From this results a value for the Hubble constant (62.3), which is the same on all scales despite the clumpy distribution of galaxies. Conclusions about dark energy and the age of the Universe will be discussed.

Silicate emission in circumstellar disks: grain growth or grain porosity?

Special Colloquium
Prof. Nikolaj Voshchinnikov
ORATED
St. Petersburg University, Russia

The flat shape of the 10mum silicate band observed in the spectra of T Tau and Herbig Ae/Be stars is usually attributed to the growth of compact grains in circumstellar disks. We show that much smaller, but very fluffy particles give rise to a similar band shape. We discuss the optical properties of such aggregate particles and show that by varying the porosity and the volume fraction of carbon, one can reproduce any observed profile of the 10 mu band.

The Cores of Dark Matter Halos - A problem for CDM?

Special Colloquium
Dr. Erwin de Blok
ORATED
Mount Stromlo Observatory, Australian National University

Low Surface Brightness (LSB) galaxies are dominated by dark matter. Recent high-resolution rotation curves suggest that their total mass-density distributions are dominated by constant density cores, rather than the steep and cuspy distributions found in Cold Dark Matter simulations. The data are best described by a model with a soft core with an inner power-law mass-density slope alpha = -0.2 +- 0.2. No single universal halo profile provides an adequate description of the data and the observed mass profiles appear to be inconsistent with LambdaCDM simulations. We have modelled the impact of many systematic observational effects, and find that no single effect can reconcile the data with cuspy CDM halos. I will also present some new observations that may contribute to a solution for this longstanding problem.

Colloquium on SKADS Simulations

Informal Colloquium
Dr. Torsten Enßlin
ORATED
MPA Garching

Informal Colloquium on SKADS Simulations Friday, March 10, Room 3.25 09:30 Andre Waelkens (MPA, Garching) “A tool for simulating Galactic synchrotron emission” 10:00 Torsten Ensslin (MPA, Garching) “Statistical methods to study MHD turbulence using radio polarization” 10:30 Break 10:45 Informal discussion (R. Beck/W. Reich)

Compact high Velocity Clouds and Dwarf Galaxies

Special Colloquium
Prof. Edwin E. Salpeter
ORATED
Cornell University, USA

TBA

Noisy Jets and Emission Components in Galactic X-Ray Binaries

Main Colloquium
Dr. Tomaso Belloni
ORATED
INAF - Osservatorio Astronomico di Brera, Merate, Italy

The discovery of relativistic jets in galactic X-ray binaries allowed us to identify an essential element for the understanding of the emission from these systems. Focussing on bright transients, I show that a global analysis of the available data leads to the identification of a surprisingly precise phenomenology common to all systems. In addition to the main hard and soft states, a clear an unambiguous characterization of the intermediate states is evident from the data. I present the fundamental timing and spectral properties of these states and their relation to the jet ejection. From the correlation of spectral and timing properties in the X-ray band and of the available radio data, the global properties of variability emerge as a fundamental tracer for the identification of the origin of the main emission components. The times are now ripe for a more detailed comparison of the jet/accretion relation in galactic systems and active galactic nuclei.

X-ray illumination: X-ray-Dominated Regions versus Photon-Dominated Regions

Special Colloquium
Rowin Meijerink
ORATED
Sterrewacht Leiden

Gas clouds in centers of galaxies are exposed to intense radiation fields, originating from an active galactic nucleus (AGN), a starburst region or both. OB stars dominate the radiation from starbursts which is mostly in the far-ultraviolet (6 < E < 13.6 eV), while AGNs emit radiation in the X-ray regime (E > 1 keV). Resulting thermal and chemical gas structures are quite different for the two cases. FUV photons turn cloud surfaces into Photon Dominated Regions (PDRs), while X-rays penetrate deep into cloud volumes creating X-ray dominated regions (XDRs). The thermal and chemical processes important in XDRs and PDRs are discussed. The resulting line intensities for a number of species are shown and a comparison between XDRs and PDRs is made.

Precision Astronomy by Technical Development: Festkolloquium honoring Prof. Wielebinski on the occasion of his 70th birthday

Special Colloquium
Multiple Speakers: Check abstract for details
ORATED


Speaker: J.A. Zensus/T.L. Landecker/J.L. Han/M. Kramer/H. Lesch/N. Bartel Affiliation: MPIfR/NRC, Canada/NAO, China/Jodrell Bank, UK/Uni Muenchen/York U., Canada Festkolloquium honoring Prof. Richard Wielebinski on the occasion of his 70th birthday Friday, 17 February 2006 HS 0.03 Precision Astronomy by Technical Development 14:00-14:10 J.A. Zensus Welcome 14:10-14:50 T.L. Landecker Precision Polarimetry 14:50-15:30 J.L. Han Faraday Rotation Sky 15:30-16:00 Coffee break 16:00-16:40 M. Kramer Binary Pulsars as Gravity Lab 16:40-17:20 H. Lesch Nanosecond Pulses 17:20-17:50 N. Bartel VLBI Astrometry of the Guide Star for Gravity Probe B 17:50-18:15 Movie “Testing Einstein’s Universe” 18:15-18:30 R. Wielebinski Summary 18:30 Reception

Ultra-compact dwarf galaxies - discovery and interpretation of a new kind of astronomical object

Special Colloquium
Dr. Michael Hilker
ORATED
AIfA

The name “Ultra-Compact Dwarf Galaxy” (UCD) was invented for a new type of astronomical object that has been discovered in cores of nearby galaxy clusters some years ago. UCDs resemble globular clusters, but are up to 100 times more massive and slightly more extended. Their luminosities are comparable to those of nuclei of the most massive dwarf ellipticals or late-type spirals. Various formation scenarios have been brought forward to explain the origin and evolution of UCDs. Two of them seem to be most promising: first, UCDs might be the remnant nuclei of galaxies that have been disrupted in the cluster environment. Second, UCDs might have formed from the agglomeration of many young, massive star clusters that were created during ancient merger events. In this talk I will present the history on the discovery of UCDs and our current knowledge about these enigmatic objects. I will discuss their relation to the brightest globular clusters of nearby galaxies (like omega Centauri in the Milky Way) and to other types of compact dwarf galaxies (like M32 in Andromeda). Finally, I will give an outlook on what can be learned from UCDs with respect to galaxy and galaxy-cluster formation, and what cosmological lessons might be gleaned from them.

Jets from Young Stars

Special Colloquium
Dr. Jochen Eisloeffel
ORATED
Thueringer Landessternwarte, Tautenburg

Accretion and the ejection of collimated flows are the driving processes at the heart of objects from forming stars to the central engines of active galaxies. As the nearest of these objects young stars allow us to study these processes in unequaled detail. In the first part of this talk I will give an overview of jets from young stars, their general observed properties and models of their formation. In the second part I will present recent HST observations providing new insights about the outflow engine and its jet production. Finally, I will outline how future instruments (including VLTI, ALMA, LOFAR) may help us to understand the accretion/ejection process in young stars and beyond.

The initial conditions of high mass star formation

Special Colloquium
Thushara Pillai
ORATED
MPIfR

Studies in the field of star formation have led to a good understanding of low mass star-formation. However there are both theoretical and observational challenges that hinder a similar understanding of high mass star-formation. Studies on the initial stages of high mass star formation would be the best strategical advance for observers. Only recently have clouds with the potential of forming high-mass stars and /or clusters, but still yet largely devoid of stellar objects, been identified: Infrared Dark Clouds. As part of my PhD thesis, I conducted a comprehensive observational study of infrared dark clouds (IRDCs). IRDCs are cold, dense molecular clouds seen in silhouette against the bright diffuse mid-infrared (MIR) emission of the Galactic plane. The main objective was to identify the physical and chemical properties of the massive cores embedded in IRDCs, the progenitors of high-mass stars. I will present observations made with mm/cm single dish telescopes, interferometers and mid-infrared data from Space Telescopes (MSX/SPITZER) for the study. I find that IRDCs harbour precluster cores which are gravitationally bound and turbulent. These cores show a high degree of deuteriation and depletion. In some cases cores harbour clusters at a very early evolutionary stage showing that massive stars can form within IRDCs. This work has provided evidence that within IRDCs, the long sought progenitors of high mass stars can be found.

Europe in space: taking off without the public?

Main Colloquium
Dirk Lorenzen
ORATED


July 2004: NASA has the Cassini spacecraft in orbit around Saturn: since then each day a new picture is released. January 2006: ESA has now had a wonderful spacecraft in orbit around Mars for two years: a mere 50 Mars Express images are online. The Hubble Space Telescope is fascinating the public worldwide with marvellous pictures almost on a weekly basis. Europe operates the hardly known Very Large Telescope (VLT) in Chile, considered the world’s most powerful observatory. In 2004, the VLT published as few as five ”Hubble class” pictures. These are two random examples of a lack of proper communication of Europe’s space and astronomy activities. This talk - it should be more a discussion - will address a few key issues on what’s going wrong in Europe: Why are many scientists so reluctant to communicate their research to the public? Why isn’t public relations work an integral part of any project financed by the European taxpayer? What are the constraints of a public outreach officer’s professional routine? What do scientists experience when they talk to journalists? Is a scientific observation or a scientific paper really more important than a good picture making the front page of newspapers throughout Europe?

From star formation to planetary systems: Observations in the submillimetre

Main Colloquium
Dr. Jane Greaves
ORATED
University of St Andrews, UK

Submillimetre observations trace the coolest material in the Galaxy, from stars at their earliest times to comets at the furthest outskirts of planetary systems. I will present observations made with SCUBA and mm-receivers at the JCMT, concerning some of the puzzles in how planets emerge from the dynamic environment in which stars are born. Some novel applications, such as planet detection, will be discussed. In the future, surveys and imaging can make major breakthroughs in star and planet formation, and I will briefly talk about exciting prospects with JCMT, APEX and ALMA.

On the origin of cosmological seed magnetic fields by kinetic plasma instabilities

Main Colloquium
Prof. Reinhard Schlickeiser
ORATED
University of Bochum

The existence of magnetic fields is a mandatory requirement for the onset of most nonthermal phenomena in cosmological sources, especially gamma-ray burst sources and relativistic jet sources. The processes leading to the magnetization of the intergalactic medium are not yet known. Seed magnetic fields are needed for the often invoked dynamo process to amplify them. As a novel mechanism to generate cosmological seed magnetic fields the Weibel-instability and the counterstream-instability are proposed. Both kinetic instabilities rely on anisotropic velocity distribution functions of electrons and ions in the fully ionized non-magnetized intergalactic medium. With kinetic particle-in-cell simulations and analytic linear instability calculations I demonstrate that these instabilities give rise to aperiodic (real frequency part omega _R=0, imaginary frequency part Gamma >0) transverse electromagnetic fluctuations with large spatial scales that can serve as seed fields. Anisotropic velocity distribution functions of the ionized baryonic matter result e. g. from their large-scale motions in the gravitational potential dominated by darked energy and dark matter.

Isolated X-ray Thermal Neutron Stars - the Magnificent Seven and beyond

Special Colloquium
Dipl.-Phys. Bettina Posselt
ORATED
MPE, Garching

The Magnificent Seven are exceptional neutron stars because of their blackbody-like soft X-ray spectra and no detected radio emission. Since their discovery with ROSAT they have been intensively studied in X-ray and in the Optical as they may provide valuable constraints on the equation of states of neutron stars. Meanwhile we know five of them as X-ray pulsars and pulse period derivatives together with interesting absorption features point to strong magnetic fields in the order of 1013 Gauss. It is discussed whether they may be the “”connection“” between ordinary pulsars and the Anomalous X-ray pulsars and Soft Gamma-ray repeaters. However, seven is a number far to small for sufficient statistical studies. I will summarise the current knowledge about the Magnificent Seven and present our search for new isolated X-ray thermal neutron star candidates.

A GMRT study of extremely faint dwarf galaxies

Main Colloquium
Dr. Ayesha Begum
ORATED
Tata Institute of Fundamental Research, Mumbai, India

I will present the results obtained from a study of very faint (M_B>-13.5 mag) dwarf irregular galaxies with the Giant Metrewave Radio Telescope (GMRT). We find that all of our sample galaxies show systematic large scale velocity gradients, unlike earlier studies which found the velocity field of such galaxies to be chaotic. For some of our galaxies, the velocity fields are completely consistent with ordered rotation, though often the peak circular velocities are comparable to the velocity dispersion. These are the faintest known galaxies with such regular kinematics. We use our observations to investigate the dark matter distribution in the individual galaxies, as well as to search for systematic trends ( such as those predicted from hierarchical structure formation models) in the dark halo parameters of galaxies of different sizes. Further, we study the interplay between HI distribution and star formation in faint dwarf galaxies, from which we find that the general unifying patterns between gas distribution and star formation, seen in the spirals and brighter dwarfs, seems to be absent in faint dwarf galaxies. Finally, I will describe the visibility based formalism which we have developed for determining the power spectrum of the HI intensity fluctuations in faint dwarf galaxies, where the expected signal is very weak. I will compare the power spectrum in our faint, largely quiescent galaxies, with those observed in much brighter galaxies.