The first station of the Long Wavelength Array

Special Colloquium
Dr. Frank Schinzel
ORATED
MPIfR

Construction of the first station of the Long Wavelength Array (LWA1) was completed  1.5 years ago. The LWA1 has since been undergoing commissioning and its first science observations from two calls for proposals. The LWA1 is co-located with the Very Large Array and consists of 262 dual-polarization dipoles, the signals of which are digitized and combined into beams. Four independently-steerable dual-polarization beams are available, each with two tunings of 16 MHz bandwidth that can be independently tuned to any frequency between 5 and 88 MHz. I am going to present a brief overview of the station architecture and early science results demonstrating the versatile capabilities of this new instrument. These among others include observations of Pulsars, Solar/Jupiter bursts, ionospheric fluctuations, transients, and imaging of lightning. In this context I am also going to briefly discuss progress made towards the detection of the cosmological dark ages.

ESO50: fifty highlights from 50 years

Main Colloquium
Dr. Michael Hilker
ORATED
AIfA

The year 2012 marks the 50th anniversary of the European Southern Observatory (ESO), the foremost intergovernmental astronomy organisation in the world. I will present 50 selected historical and scientific highlights from ESO’s first 50 years.

MAPPING THE MILKY WAY WITH THE VLBA AND THE VLA

Lunch Colloquium
Dr. Andreas Brunthaler
ORATED
MPIfR

We are conducting two large suverys to map the Milky Way. The Bar and Spiral Structure Legacy (BeSSeL) Survey uses the VLBA to measure accurate parallaxes and proper motions of sever hundred masers in Galactic star forming regions. This will result in a catalogue of accurate distances to most Galactic high mass star forming regions visible from the northern hemisphere and very accurate measurements of fundamental parameters such as the distance to the Galactic center (Ro), the rotation velocity of the Milky Way (Thetao), and the rotation curve of the Milky Way. Furthermore, the VLA will be used for a C-band continuum and spectral line survey of the Galactic plane. A report of the first results of BeSSeL and results from a pilot project of the Galactic plane survey will be presented.

A Novel Satellite Navigation Technology using Pulsar Signals

Main Colloquium
Dr. Werner Becker
ORATED
MPE Garching

An external reference system suitable for deep space navigation can be defined by making use of the characteristic signals emitted from pulsars. Their periodic signals have timing stabilities comparable to atomic clocks and provide characteristic temporal signatures that can be used as natural navigation beacons, quite similar to the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board the spacecraft with predicted pulse arrivals at a reference location, the spacecraft position can be determined with an accuracy of a few kilometers, autonomously and everywhere in the solar system and beyond. The unique properties of pulsars make clear already today that such a navigation system will have its application in future astronautics. We report on the current development status of this novel technology.

Seed Fields for Dynamos and Cosmology

Special Colloquium
Prof. Dr. Dmitry Sokoloff
ORATED
Moscow State University

Large-scale magnetic fields in celestial bodies like galaxies are believed to be excited by dynamos, driven by differential rotation and mirror-asymmetric convection. This mechanism needs a weak seed magnetic field which can be created by a battery mechanism in a protogalaxy or may have survived from the pre-recombination times. Researchers in galactic magnetism strongly prefer the first option, however it is difficult to eliminate the second one. The problem becomes more attractive after a recent claim that the intergalactic space contains substantial magnetic fields, presumably of a cosmological origin. I will discuss what kind of cosmological seeds can be expected and their imprints.

Connecting the local star formation law and the growth of embedded clusters

Main Colloquium
Dr. Genevieve Parmentier
ORATED
Astronomisches Rechen-Institut, Heidelberg

Evidence favouring a Gaussian initial globular cluster mass function similar to that observed today has accumulated over recent years. I investigate how the shape of the initial cluster mass function is affected by expulsion from the protocluster of the leftover star forming gas due to supernova activity. Owing to the weakening of its gravitational potential, the protocluster retains a fraction only of its newly formed stars. The mass fraction of bound stars extends from zero to unity depending on the star formation efficiency achieved by the protoglobular cloud. Such wide variations may affect the mapping of the protoglobular cloud mass function to the resulting initial globular cluster mass function. I show that a bell-shaped cluster mass function with the observed width and the right turnover may be the imprint of the gas removal phase, provided that the protoglobular clouds have a characteristic mass of about 10^6 Msol.

The fragile nature of pre-planetary dust evolution

Special Colloquium
Dr. Gerhard Wurm
ORATED
Institut für Planetologie, Universität Münster

In early phases of planet formation the growth and destruction of dust aggregates are major processes. There is not one simple way leading up on the particle size ladder from dust to planetesimals. In laboratory experiments there is growth, fragmentation and bouncing in classical collisions but we also see more “strange” processing of illuminated bodies which can be eroded to dust again very efficiently. These might all be important to assemble the picture of particle evolution, recycling and transport in protoplanetary disks or planet formation, eventually.

Pulsar scintillations: current sheets in the ISM?

Lunch Colloquium
Dr. Jonathan Braithwaite
ORATED
AIfA

Pulsar scintillations are a little bit like the twinkling of stars, caused by differences in the speed of light in the warm ionized ISM. From them, we infer the presence of over-dense structures, and there is reason to believe that they have a sheet-like geometry. These structures are probably too small to be self gravitating, and could be ’magnetic domain boundaries’, or in other words, current sheets, where the extra gas pressure is confined by magnetic pressure. I present the results from some simple simulations which demonstrate how such current sheets could form spontaneously, and review some fun topological properties of magnetic fields.

Catch me if you can: Is there a 'runaway-mass' black hole in the Orion Nebula Cluster?

Main Colloquium
Dr. Ladislav Subr
ORATED
Astronomical Institute, Charles University,Prague

The Orion Nebula Cluster (ONC) is one of the best studied young star clusters. The observational data, however,i seem to be inconsistent with theoretical expectations. The most remarkable is a lack of massive stars and highly supervirial velocity dispersion in the cluster core. I will present results of numerical modelling of initially compact star cluster which has undergone phase of rapid two-body relaxation and gas expulsion. After few million years of dynamical evolution, the model apparently reconstructs all observational properties of the ONC. In particular, we suggest that strong few-body interactions among massive stars in the cluster core lead to high velocity ejections and to direct stellar collisions which lead to formation of a runaway-mass star and, consequently, a black hole hundred times more massive than the Sun.

Evidence of large-scale helical magnetic field in the quasar 3C454.3

Lunch Colloquium
Dr. Mohammad Zamaninasab
ORATED
MPIfR

A sequence of high angular resolution radio images of 3C454.3 taken within the last decade shows a strong outburst that released a bright superluminal arc-like feature illuminating parts of the collimated flow which had not been visible before and thus providing a unique opportunity to study the transverse structure of the jet. Multi-frequency polarimetric radio imaging of the outflow shows significant transverse asymmetries in intensity, spectral index, linear polarization and Faraday rotation measure, as is expected in the presence of a large-scale helical magnetic field. Our results provide direct observational support to the magnetic jet launching models and demonstrate the stability of the ordered field component over a large distance.

Black Holes: from the origin to the future. A virtual trip throughout the violent Universe

Main Colloquium
Prof. Dr. Pietro Ubertini
ORATED
Istituto di Astrofisica Speziale e Fisica Cosmica, Rome, Italy

We will perform a virtual trip throughout the Universe hunting black Holes with the INTEGRAL satellite, giving a glance at the sky with ‘gamma-ray’ eyes. We will travel in the known Universe looking at the most violent phenomena, virtually diving inside giant black holes at the border of the Universe, at his dawn, now detected with the new Space Observatories. The study of the initial moment of the Universe lifetime allow us to understand how it is evolved from the Big Bang, when it was basically all hydrogen and dark matter, till now, populated by all kind of black holes: from the ‘mini’ ones to the gigantic, placed at it boundaries. How and when the ‘first star’ was born, is still an unresolved astrophysical mystery: a missing link between the initial stage of the cosmos and the sky we see every night.

Magnetic Fields and Molecular Cloud Fragmentation

Special Colloquium
Dr. Shantanu Basu
ORATED
Western University, London, Canada

I review a series of recent models on the effect of magnetic fields and ambipolar diffusion on the fragmentation process in molecular clouds. Cosmic ray ionized zones within molecular clouds show a dramatic dependence of fragmentation scale upon the ambient mass-to-flux ratio, if it is in the transcritical regime. This can lead to a broad core mass function. Highly ionized envelopes may maintain long-lived wave modes as well as lead to an initial pc-scale fragmentation process that may be associated with the formation of cluster-forming clumps.

Optical interferometric image reconstruction and its application to the enigmatic eclipsing binary epsilon Aurigae

Lunch Colloquium
Dr. Brian Kloppenborg
ORATED
MPIfR

Within the last few years the number of published images from optical interferometers have dramatically increased. With present and next-generation instruments combining light from four to six telescopes, image reconstruction will become a mainstream diagnostic tool for optical interferometrists. In this talk I will introduce the optical interferometric observables, outline the theory of image reconstruction, explain how present algorithms solve this ill-posed non-convex problem, and discuss failures/inadequacies of current techniques. I will conclude my talk by discussing how image reconstruction solved a 190 year mystery by observing epsilon Aurigae during its 2009-2011 eclipse.

Magnetic Accretion: Back in Business

Main Colloquium
Dr. Nazar Ikhsanov
ORATED
Pulkovo Observatory & Korea Astronomy and Space Science Institute

Accretion process is usually considered under assumption that the material captured by an accretor from its environment is non-magnetized. This leads to the traditional scenarios of spherical and Keplerian disk accretion. If the material in the environment of the accretor is magnetized the accretion picture differs from the traditional. In this case accretion occurs through a non-Keplerian slab in which the material is confined by the magnetic field of the accretion flow itself. This magnetic accretion scenario had been initially suggested more than 40 years ago. Since that time it has been elaborated analytically and numerically and applied to the case of accretion onto a black hole. However, observational verification of its predictions turned out to be very complicated. Due to this reason the magnetic accretion remained in shadow of the traditional views until recently. A step forward in the development of this approach was made this year when the magnetic accretion scenario has been applied to interpreting the process of accretion onto a neutron star. It appears the only accretion model which allows us to explain the observed spin evolution of long-period pulsars. In my talk I review state-of-the-art of the magnetic accretion scenario and briefly discuss possibilities of its application to the description of accretion-powered objects of different types.

Molecular lines in Luminous Infrared Galaxies: the shifting of two paradigms

Lunch Colloquium
Dr. Padelis Papadopoulos
ORATED
MPIfR

I will describe results from the largest molecular line survey (CO, 13CO, HCN) of Luminous Infrared Galaxies (LIRGs) conducted using the JCMT and the IRAM 30-m telescope, and then expanded into high frequencies (CO J=4-3 up to J=13-12) using the SPIRE/FTS aboard Herschel. It now looks that our views regarding: a) the power sources of the molecular lines, and b) the molecular gas mass estimates may have been wrong for over two decades, and the corresponding paradigms must shift accordingly.

The CHANG-ES Project

Special Colloquium
Prof. Judith Irwin
ORATED
Queen's University at Kingston, Canada

In this pre-SKA era, the upgrade of the Very Large Array to the Expanded VLA (EVLA) is providing new opportunities for exploring the nature of faint gaseous halos in galaxies. Our project, ‘Continuum Halos in Nearby Galaxies - an EVLA Survey’ (CHANG-ES) is targetting edge-on galaxies in order to understand the nature, origin, and physics of disk-halo outflows and their possible connection to the wider intergalactic environment. Observations in all four Stokes also provide opportunities for investigating the nature of halo magnetic fields. This talk will describe the CHANG-ES project, outline some of the new capabilities and technical challenges involved in using the EVLA during its commissioning phase, and present some preliminary results from the survey.

The VLBI monitor project of the 6.7 GHz methanol masers using the JVN/EAVN

Special Colloquium
Dr. Koichiro Sugiyama
ORATED
Yamaguchi University, Japan

High-mass stars are now thought to be formed through the mass accretion from the rotating disk in the similar cases of the low-mass star formation. The proper motion to confine the gas accretion from the disk of several km/s, however, is so hard to detect any tracers except for the masers with the VLBI. The 6.7 GHz methanol maser can be the best tracer for studying dynamics around high-mass young stellar objects (YSOs), and in particular trace a rotating disk because of the spatial morphology and proper motions detected in a few sources. In this time, we talk about the VLBI monitor project of this maser using the Japanese VLBI Network (JVN) and East-Asian VLBI Network (EAVN), which have started since 2010. This project, however, is now on-going, and then we show just a result of the VLBI imaging snap-shot survey observed in 2010 and 2011. All of observed 36 sources provide new VLBI images except for one resolved out source, and the spatial morphology were classified into five categories; ellipse, arched, linear, pair and complex, similar to the results by the European VLBI Network observations (Bartkiewicz et al. 2009). In the EAVN 36 sources, 24 sources except for near equatorial sources (-5< Dec <+5 deg) were also observed by using the Australia Telescope Compact Array (ATCA) to obtain spatial morphology of the 6.7 GHz methanol masers without missing flux, and then we verified and corrected classifications of the spatial morphology. We compared the corrected spatial morphology to cm radio continuum emissions, and then found that the ellipse and complex sources would be expected to be appeared earlier than the arched and linear sources on the evolution of high-mass young stellar objects.

The Interstellar Medium of Low Mass Galaxies: Magnetic Fields and Ionized Gas

Special Colloquium
Dr. Amanda Kepley
ORATED
University of Virginia, Charlottesville, USA

Low mass galaxies are the most common type of galaxy in the universe. Understanding these galaxies is critical for understanding the evolution of galaxies over cosmic time. However, the properties of these galaxies are different from the properties of their more prominent spiral cousins, which may lead to significant evolutionary differences. This talk focuses on exploring two critical components of the interstellar medium in low mass galaxies: magnetic fields and ionized gas. Magnetic fields can influence gas dynamics, provide pressure support, and accelerate and distribute cosmic rays in a galaxy, while the ionized gas is linked to the young massive star population in a galaxy. I find that magnetic fields do not dominate the ISM pressure in two low mass galaxies (NGC 4214 and NGC 1569). The structure of the magnetic fields in NGC 1569 and NGC 4214 appears to be shaped by the young massive stars rather than by a large-scale alpha-omega dynamo as in larger spiral galaxies. I also present constraints on the properties of the obscured ionized gas in NGC 1569 using an observing technique revitalized by the extraordinary flexibility of the EVLA correlator: radio recombination lines. These and other observations of the ISM in low mass galaxies by the next generation of radio telescopes are making a more detailed understanding of the ISM of these intrinsically faint galaxies possible.

New insights on the thermal properties of asteroids using infrared interferometry

Lunch Colloquium
Dr. Alexis Matter
ORATED
MPIfR

Impacting the surface temperature distribution of atmosphereless bodies such as asteroids, thermal properties like thermal inertia are essential to fully constrain the solar system minor bodies. Their determination inform us, for instance, about the nature of the asteroids’ surface and the effect of the solar irradiation on their semi-major axis through the Yarkovsky effect. Based, so far, on thermal inertia measurements of about 30 bodies, inverse correlation was found between size and thermal inertia in two size ranges (< and > than 100 km). This probably indicates significant differences in surface composition between large and never disrupted older asteroids, and smaller and re-accumulated younger ones. In this context, we developed a new approach combining thermal IR flux measurements and interferometric data to constrain the size and surface thermal properties of asteroids, taking advantage of the high angular resolution provided by interferometry. Based on a thermophysical model (TPM), which is used for the time for the interpetation of interferometric data, this new approach was applied to two large main-belt asteroids, (41) Daphne (C-type) and (16) Psyche (M-type). Whereas the (41) Daphne results (low thermal inertia) are in good agreement with the inverse correlation size-thermal inertia derived for large asteroids, (16) Psyche significantly deviates from it (higher thermal inertia). This shows evidences of a significant difference in surface nature, composition and evolution between the most common and primitive ’C-type’ main-belt asteroids and the probably ’more evolved’ M-type asteroids, possibly originating from the fragmentation of the iron core of differentiated bodies.

A new glance at the VLTI: The mid-infrared windows open by MATISSE

Main Colloquium
Dr. Bruno Lopez
ORATED
Observatoire de la Cote d'Azur

The Very Large Telescope Interferometer located on Cerro Paranal in Chile is one of the largest astronomical optical interferometer. The VLTI is part of the facility of the European Southern Observatory and consists of the array combination of the four 8.2 meters Unit Telescopes and of the four 1.8 meters Auxilary Telescopes. The european institutes are involved in the development and in the conceptual evolution of the focal instruments of the VLTI. The first generation instruments were operated in the 2000 years and several astrophysical results of importance were achieved thanks to them. An ongoing current development is the PRIMA facility and two second-generation instruments called GRAVITY and MATISSE, after their design study, are now entering in the manufacturing phase. I will focus my talki on the MATISSE science cases and consept.

The F-GAMMA program: 5 years of monitoring Fermi blazars with the Effelsberg 100-m, IRAM 30-m and APEX 12-m telescopes

Lunch Colloquium
Dr. Lars Fuhrmann
ORATED
MPIfR

I will present a status report of the F-GAMMA program which is monitoring monthly the variability and spectral evolution of more than 60 Fermi gamma-ray blazars at an unprecedented frequency range since 2007. The program covers quasi-simultaneously 12 frequencies between 2.6 and 345 GHz in a highly synchronized manner. I will focus on our recent studies and results which include (i) the characterization of the overall variability and spectral behavior of this Fermi blazar sample, (ii) a detailed radio/gamma-ray cross-band analysis using 3.7 years of Fermi data, and (iii) testing variability models in the time and spectral domain with particular emphasis on the shock-in-jet scenario.

The dynamical birth environment of planets and brown dwarfs

Lunch Colloquium
Dr. Ingo Thies
ORATED
AIfA

The recent development of protostellar and protoplanetary models and the ongoing discoveries of extrasolar systems have led to a paradigm change in understanding the origin of our Solar System and its siblings. Rather than forming quietly and in isolation, planetary systems are now understood to form in highly dynamical environments of episodically accreting discs, tidal and viscous perturbations and disc fragmentation, and thus their structure being highly dependent on the properties of the host star-forming cluster. Here we present the most recent results of our SPH computation on the evolution of perturbed discs, and the formation of brown dwarfs and massive planets. For the first time, the perturbations of gaseous circumstellar disks through passing binary stars and the consequences on the outcome of binary-induced fragmentation will be demonstrated. In addition, we discuss a possible connection between lithium-depletion in stellar atmospheres and misaligned planetary systems as a consequence of repeated accretion.

The Status of the Ultra Broadband Receiver Project

Lunch Colloquium
Dr. Paulo Freire
ORATED
MPIfR

In this talk I present a status update on the new ultra-broadband (0.6 - 3 GHz) receiver at the Effelsberg telescope. This has just been completed and is now being tested; some of the first results of these tests will be presented. I will also give an update on the status of the new broadband coherent dedispersion systems, which will greatlly improve the precision of pulsar timing.

Evidence for Filamentary Microstructure in the Ionized ISM at Sub-A.U. Spatial Scales

Main Colloquium
Bill Coles
ORATED
UC San Diego

Observations of scattering of radio pulsars has historically been interpreted in terms of homogeneous turbulence in the warm ionized phase of the ISM. Evidence is accumulating that this model is seriously in error, that the mean density and the level of turbulence are non stationary on AU spatial scales. Imaging of the scattered radiation by indirect means, suggests that a tangled filamentary model may be more accurate.

Near-field cosmology with small telescopes: searching for stellar tidal streams and faint dwarf satellites in the Local Volume

Main Colloquium
Dr. David Martinez Delgado
ORATED
MPI für Astronomie

Within the hierarchical framework for galaxy formation, minor merging are expected to shape large galaxies to this day. Our ultra-deep, wide-field imaging of some isolated spiral galaxies in the local universe with small (0.1 to 0.5-meter diameter), robotic telescopes has led to the discovery of previously undetected giant stellar structures in the halos of these galaxies, likely associated with debris from tidally disrupted satellites. The comparison with available stellar halo simulations set in a Lambda-Cold Dark Matter cosmology suggests that this could represent one of the first evidence to support the hierarchical formation scenarios predicted for the formation of galaxies similar to our Galaxy. I also present the discovery of a tidal stream around a nearby dwarf irregular galaxy with our small telescopes. This result suggests that dwarf accretion could play an important role in the star formation history and evolution of nearby dwarf galaxies. I will finish my talk with some preliminary results about the performance of tiny telescopes (0.10-0.15 meter) for discovering faint dwarf galaxy satellites around the Andromeda galaxy, a necessary observational task to shed more light on the “missing satellite” problem from the Lambda-CDM cosmology.

A new VLA view of the M82 and NGC 2146 starbursts

Special Colloquium
Dr. Josh Marvil
ORATED
NRAO

We recently completed a suite of observations of the nuclear starburst regions in M82 and NGC 2146 using the newly upgraded National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array. We extract from these data measurements of the radio continuum spectra at sim25 frequencies between 1 and 46 GHz, at each of many 1.5” synthesized beams. Strong variations in the radio spectra exist within the inner regions of these starbursts; these variations contrast with the uniform-box models often used to explain observations such as spatially-integrated galaxy radio spectra and the radio/far-IR relation. A correlation between radio spectral index and intensity is measured for the inner regions and interpreted as the superposition of optically-thin thermal and non-thermal emission processes. In the outer regions of the starburst much of the radio emission has a spectral index < -1.0, implying either radiative spectral aging is important for a significant fraction of the total radio emission, or the cosmic electron injection spectrum is substantially different than what is assumed in standard models. We also use these images to achieve an improved understanding of starburst radio morphology, with a focus on faint chimney-like structures aligned with the minor axis of each galaxy. We discuss a possible relationship between these radio structures and the outflow channels believed to be driving a superwind in these systems.

Full-Stokes Optical Interferometry

Special Colloquium
Dr. Nicholas Elias
ORATED
NRAO

In this talk, I present an overview of full-Stokes optical interferometry. Introductory material is discussed, such as definitions and the present state of the field. I show a few simple science use cases. I define types of measurements and instruments, and give two initial designs for full-Stokes instruments. The masking optical interferometer AMASING and AMASING-POL (the limited-Stokes addition) is described. Last, I show what is required for CASA to reduce full-Stokes optical interferometry data.

Studying Quasar-host Galaxy Evolution at Redshift 6 with Large Millimeter and Radio Interferometer Arrays

Main Colloquium
Dr. Ran Wang
ORATED
University of Arizona

Observations of high-redshift quasars probe the growth of supermassive black holes (SMBH) and their connections to galaxy formation at the earliest epoch. Large samples of quasars have been discovered at zsim6. We have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of zsim6 quasars using millimeter dust continuum and molecular CO emission. The results suggest massive star formation at rates of a few hundred to 1000 Msun/yr in sim30\% of these zsim6 quasars. Molecular CO line emission has been detected in 12 zsim6 quasars with estimated molecular gas masses on the order of 10^{10} Msun within the quasar host galaxies. Most of the CO-detected quasars at zsim6 follow the far infrared-CO luminosity relationship defined by actively star-forming galaxies at low and high redshifts. The median black hole-bulge mass ratio estimated with the CO measurements is about an order of magnitude higher than the present-day value. These results are in good agreement with the picture of massive star formation coeval with rapid SMBH accretion in the earliest quasar-host galaxy systems. Further high resolution imaging of the dust and gas components with ALMA will directly probe the intense star formation in the central (a few kpc) region of these starburst quasar hosts at the earliest epoch.

Physical and Chemical Properties of Protocluster Clumps and Massive Young Stellar Objects Associated to Infrared Dark Clouds

Main Colloquium
Laura Gomez
ORATED
MPI für Radioastronomie

The newly identified class of interstellar clouds now termed infrared dark clouds (IRDCs) represent excellent laboratories to study the earliest stages of high-mass star formation given that some of the clumps within them are known to have high masses (sim100’s M_{odot}), high densities (n>10^5 cm^{-3}), and low temperatures (10–20 K) as expected for the birthplaces of high-mass stars. Some questions remain unanswered: Do IRDCs harbor the very early stages of high-mass star formation, i.e., the pre-protocluster phase? Is there chemical diversity in IRDC clumps? What is the mass distribution of IRDCs? In this dissertation and for the first time, a catalog of 12529 IRDC candidates at 24 mum has been created using archival data from the MIPSGAL/Spitzer survey, as a first step in searching for the massive pre-protocluster clumps. From this catalog, a sample of sim60 clumps has been selected in order to perform single-pointing observations with the IRAM 30m, Effelsberg 100m, and APEX 12m telescopes. One IRDC clump seems to be a promising candidate for being in the short-lived pre-protocluster phase. In addition, molecular line mapping observations have been performed on three clumps within IRDCs and a detailed chemical study of 10 molecular lines has been carried out. Six IRDC complexes have been mapped in the 870 mum dust continuum emission with the LABOCA instrument on the APEX 12m telescope. The mass spectrum of these clumps has been fitted with a power-law whose best-fitting index is alpha=-1.60. This value is consistent with the CO clump mass function reported in the literature. A study with the Plateau de Bure Interferometer of a core in an archetypal filamentary IRDC at few arcsecond resolution has been carried out, finding that methanol abundances are enhanced and provinding evidences for the presence of an outflow almost in the East-West direction.

Recent Results from the CHARA Array

Main Colloquium
Dr. Theo ten Brummelaar
ORATED
The CHARA Array-Georgia State University-Mount Wilson Observatory

The CHARA Array is a six telescope optical/IR interferometer on the grounds of the Mount Wilson Observatory just North of Los Angeles. CHARA is operated by Georgia State University and has a broad range of collaborators. There are currently six beam combiners, two for visible and four for near infrared, working including the MIRC instrument that can combine all six telescopes and perform full imaging, including a snap shot mode In this talk I will give an overview of the status of the instrument and discuss some of the more recent scientific results with a focus on the imaging done at CHARA.

Cosmic Rays in Star-Forming Galaxies: Insights from Radio and Gamma Rays

Special Colloquium
Dr. Brian Lacki
ORATED
Institute for Advanced Study, Princeton, and NRAO

Most of the radio emission of galaxies comes from the synchrotron radiation of cosmic ray (CR) electrons in magnetic fields. These CRs are associated with star-formation processes. Our observational capabilities for studying CRs, both in the radio and other wavelengths, has grown vastly since then. On the radio side, we have learned that most star-forming galaxies lie on the ”far-infrared radio correlation”, a tight, linear relationship between the infrared and radio luminosity of galaxies. In recent years, we have also started detecting other star-forming galaxies in gamma-rays. I will discuss my work on CRs, and the radiation they emit, using one-zone steady-state models of CR spectra in galaxies and starbursts. I will describe a conspiracy that set the radio luminosity of starbursts, how it may work, and its implications for magnetic fields in galaxies and the correlation at high redshift. I will also discuss the implications of the recent gamma-ray detections of starburst galaxies on how CR protons are transported in them, how CR electrons cool in starbursts, and the magnetic fields in these galaxies. If time permits, I will speculate on the physical reason for the magnetic field strengths in starburst galaxies.

Cosmological interpretation of large X-ray cluster surveys with CR-HR diagrams

Special Colloquium
Dr. Nicolas Clerc
ORATED
MPI für Extraterrestrische Physik

Large samples of galaxy clusters collected in X-ray observations are able to tightly constrain cosmological scenarios by probing the mass function of large structures and its evolution with time. It is clear now that selection effects, mass-observable relation, cosmological model and related uncertainties must be jointly apprehended in order to fully and correctly exploit such surveys. The CR-HR method I will present in this talk relies on X-ray observables only – Count-Rates and Hardness Ratios of clusters in different energy bands – and thus bypasses the computation of mass for each individual cluster. By modeling the observed sample of cluster properties down to the instrumental level, it self-consistently includes the various model uncertainties. I will show how it can be applied to large cosmological X-ray surveys by presenting forecasts in realistic situations. Then I will present the results we obtained from our large (sim90 deg2), serendipitous XMM-Newton cluster survey, X-CLASS. I will put particular emphasis on cluster X-ray scaling laws, and underline some inconsistencies with recent analyses. I will finally discuss the applicability of this method to large upcoming surveys, e.g. the eRosita full-sky survey.

Imaging Pulsar Polar Caps with Nyquist-limited Scintillation Statistics

Special Colloquium
Michael Johnson
ORATED
University of California at Santa Barbara

Diffractive interstellar scintillation can be used to image pulsars with remarkable resolution. The scattering material acts as an AU-scale stochastic lens, with a corresponding diffractive scale of thousands of kilometers. We present novel statistical techniques that describe the distribution of flux density, measured with Nyquist-limited resolution. These techniques resolve the emission structure at a few percent of the diffractive scale and can identify the emission structure of individual pulses. We analyze GBT observations of the Vela pulsar at 800 MHz, which yield  100 picoarcsecond resolution – a few kilometers at the pulsar and nearly the size of the polar cap. We discuss the implications for pulsar emission physics and the capabilities of future observations.

SMA observations of Magnetic Fields in Massive Star-Forming Region DR21(OH)

Main Colloquium
Prof. Shih-Ping Lai
ORATED
National Tsing-Hua University, Taiwan

We present the dust and CO polarization detections obtained with the Submillimeter Array (SMA). The data is part ofi the SMA Legacy Project ”Filament, Magnetic Fields, and Star Formation” which is aiming at imaging polarization ati the 345 GHz band in a large sample of dense filaments forming massive stars to order to investigate the role of magnetic fields in filament and star formation. Among the data we have obtained, DR21(OH) shows strongest polarization detection. Our results are consistent with previous BIMA results and provide more details in the field geometry. I will present the implication of our results to filament and massive star formation.

Non-thermal emission from galaxy clusters: origin and future observations

Special Colloquium
Dr. Gianfranco Brunetti
ORATED
INAF Bologna

Radio observations demonstrate the existence of non-thermal particles and magnetic fields in galaxy clusters via the detection of diffuse, Mpc-scale, synchrotron emission in a fraction of nearby clusters. The presence of clusters scale non-thermal emission correlates with the dynamical properties of the hosting clusters, suggesting that clusters mergers play a role for the origin of the non-thermal activity. Interestingly, a fraction of the energy that is dissipated during cluster-cluster collisions can be channeled into particle acceleration mechanisms associated with shocks and turbulence driven in the ICM, thus providing a intriguing connection between cosmology and astro-particle physics. After reviewing the most important observational constraints, from radio to gamma-ray observations, I will outline the present theoretical scenario for the origin and evolution of non-thermal components in galaxy clusters. Finally I will discuss the potential impact of future radio observations in the field, in particular with LOFAR surveys.

Our Galactic Center, powered by a BD ?

Lunch Colloquium
Prof. Wolfgang Kundt
ORATED
AIfA

A number of broadband maps and graphs of Sgr A and its surroundings will be shown which are not easily recovered from the literature, none of which are consistent with a SBH, such as:(i) the metal-enriched super-wind from Sgr A* (10-2.5 M(sun)/yr at v = 103 km/s), (ii) the Galactic twin-jet, at 0.5, 102pc distance from the center, (iii) the hard and flaring spectrum of Sgr A*, partially recovered from its light echo at X-rays, (iv) the non-pointlike potential of Sgr A* deduced from S2, (v) Sgr A East as a transient storage bubble for pair plasma which feeds (vi) the halo-sized Galactic chimneys, and Sofue’s (hard) bipolar hypershells. All these facts give preference to a Burning Disk (BD) over a Black Hole.

Testing the No-Hair Theorem with the Event Horizon Telescope

Main Colloquium
Prof. Dimitrios Psaltis
ORATED
University of Arizona

The Kerr spacetime of spinning black holes is one of the most intriguing predictions of Einstein’s theory of general relativity. The special role this spacetime plays in the theory of gravity is encapsulated in the no-hair theorem, which states that the Kerr metric is the only realistic black-hole solution of the vacuum field equations. Recent and anticipated advances in the observations of black holes throughout the electromagnetic spectrum have secured our understanding of their basic properties while opening up new opportunities for devising tests of the Kerr metric. In this talk, I will show how observations of accreting black-holes with current and future instruments will lead to the first direct test of the no-hair theorem with astrophysical objects. I will also discuss the current state of the Event Horizon Telescope, which will obtain, in the near future, the first horizon-scale image of the black hole in the center of the Milky Way.

Neutron Star Radii and Masses: A Window To The Physics of Dense Matter

Special Colloquium
Prof. Feryal Ozel
ORATED
University of Arizona

Neutron stars offer the unique possibility of probing the equation of state of cold, ultradense matter. Understanding the properties of the neutron star interior is also important for predicting the observational appearance of short gamma-ray bursts, the end stages of neutron star coalescence, and the outcomes of supernova explosions. I will present the recent measurements of neutron star radii and masses. I will show how the combination of the tightly constrained radii and the currently known pulsar masses allows for the first astrophysical inference of the pressure of cold matter above nuclear saturation density. I will discuss the implications of this measurement for nuclear theory and astrophysics.

The Mega-maser Cosmology Project

Main Colloquium
Prof. Fred Lo
ORATED
NRAO

In this era of precision Cosmology, an independent determination of the Hubble Constant, Ho, the current expansion rate of the Universe, to 1such as the nature of dark energy, the curvature of the universe, the number of families of relativistic particles. The Mega-maser Cosmology Project (MCP) is aimed at determining Ho to high accuracy via angular diameter distance determination using circum-nuclear disks traced by water maser emission (mega-maser disks) in Seyfert 2 galaxies in the Hubble flow. We will explain the mega-masers and their application to distance determination, the current status and future prospects of the MCP. An important by-product of the MCP is the precise determination of the enclosed (black hole) mass of the mega-maser disks in Seyfert 2 galaxies. These measurements show that the M-sigma relationship defined by more massive elliptical galaxies may not hold for galaxies with lower sigma.

Complex organic molecules in the interstellar medium: pushing the limits with millimeter-wavelength spectroscopy

Lunch Colloquium
Dr. Arnaud Belloche
ORATED
MPIfR

Almost 170 different molecules have been discovered in the interstellar medium (ISM) or in circumstellar envelopes of late-type stars so far. These molecules still have a limited degree of chemical complexity. In contrast, the molecular inventory of meteorites found on Earth includes more than 80 distinct amino acids (the building blocks of proteins), with a composition suggesting an interstellar origin. However, none has been detected in the ISM so far. The key site to search for new complex organics in the ISM is the star-forming hot molecular cloud core Sgr B2(N). I will present our single-dish line survey of this source and describe the technics used to decipher its molecular content. This analysis led to the detection of several new species and will serve as a solid basis for the search for new complex organics in future ALMA observations, in particular in the frame of a project accepted for the first year of operation (Cycle 0). I will discuss the perspectives offered by this new, powerful interferometer in this context.

Supernova Remnants in Distant Galaxies

Special Colloquium
Prof. You-Hua Chu
ORATED
University of Illinois

The high angular resolution of the Hubble Space Telescope opened a new window for us to study supernova remnants (SNRs) in distant galaxies. For example, a SNR with a 10 pc diameter extends 0.2 arcsec at a distance of 10 Mpc, and can still be resolved by HST images with a pixel size of  0.05 arcsec/pixel. We have used HST images of M101 to study its SNRs. The H-alpha images were used to identify the SNR candidates that were previously identified from ground-based H-alpha and [S II] images. The continuum images were used to study the underlying stellar population, the presence or absence of a population of massive stars. It is possible to use the interstellar and stellar environments of each SNR candidate to assess its nature. We find that the largest SNR candidates are superbubbles. Among the “confirmed” SNRs, about 1/4 are likely associated with Type Ia SNe and 3/4 core-collapse SNe. This ratio is consistent with the observed ratio for spiral galaxies. Recently we are exploring the possibility of detecting Type Ia SNRs in elliptical galaxies. Using the Type Ia SNRs in the Large Magellanic Cloud as template, we find that Type Ia SNRs can be detected somewhat easily at  5 Mpc and with difficulty at  10 Mpc. I will use HST H-alpha images of the elliptical galaxy Maffei 1 at 3-4 Mpc to illustrate the search for Type Ia SNRs. Global statistics of SNRs in other galaxies provide an independent means to estimate SN rates.

Testing General Relativity in the Strong-Field Dynamical Regime

Special Colloquium
Dr. Clifford Will
ORATED
Washington University, St. Louis

General relativity has been well-tested in the weak-field slow-motion regime of the solar system. In binary pulsar systems, some tests of strong-field aspects of the theory have been carried out. In the future, testing GR in the strong-field, highly dynamical regime will be an important theme in experimental relativity. We describe a number of possible tests that could be carried out, including tests using astrophysical phenomena around black holes, tests using gravitational waves, and tests of black hole no-hair theorems using high-precision observations of stars orbiting our galactic center black hole.

How to detect baryonic acoustic oscillations using integrated neutral hydrogen emissio

Main Colloquium
Dr. Ian Browne
ORATED
University of Manchester, UK

Baryon Acoustic Oscillations (BAO) are an important probe of the Universe, in particular their detection and quantification at moderate redshifts can constrain the equation of state of dark energy. I will give a brief review of existing measurements and future plans. This will focus on radio measurements using redshifted neutral hydrogen emission. I will present an outline plan for an innovative and economical instrument, BINGO, designed to measure BAO in the redshift range 0.2 to 0.5. This plan is backed up by careful simulations of the expected signal and performance of the proposed instrument. I will conclude by confronting the challenges of removing systematics and astrophysical foregrounds.

The central region of quasars seen with gravitational microlensing

Lunch Colloquium
Dr. Dominique Sluse
ORATED
AIfA

Our detailed understanding of the working engine of quasars is still incomplete. Several basic questions remain, such as: How is the supermassive black hole in the center of quasars fed? What is the geometry and kinematics of the gas flow near the black hole? The answer to these questions is still elusive, mainly because the inner regions of the quasars remain unresolved by current telescopes. Gravitational microlensing, produced by the stars in lensing galaxies of strongly-lensed quasars, provide us with a natural telescope which scans quasars on sub-parsec scale. In this talk, I will describe the effect of microlensing on multiply-imaged quasar spectra and show how microlensing-induced deformations can be unveiled. I will explain how the study of these effects allows us to measure the temperature profile of the accretion disk, to estimate the size and study the geometry of the region emitting the quasar broad emission lines.

TBA

Special Colloquium
Dr. Alessandro Patruno
ORATED
Astronomical Institute A. Pannekoek, University of Amsterdam

TBA

Studying multi-wavelength gamma-ray burst afterglow emission using numerical simulations

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

The afterglow emission following gamma-ray bursts (GRBs) contains information about the nature of both the GRB outflows and the circumburst medium in which they are propagating. We use the relativistic magnetohydrodynamic (RMHD) numerical simulations to study the dynamics of arbitrarily magnetized GRB ejecta. Using radiative transfer code we compute the multi-wavelength (radio, optical and high-energy) light curves from the results of our RMHD simulations, and show that most of the GRB ejecta need to be moderately-to-strongly magnetized at the onset of the afterglow for the early afterglow of most GRBs to be explained. We apply our model to study the early optical light curves of GRB 990123 and GRB 090102. Finally, we study the radiative signature of a blast-wave propagating into a complex circumburst environment formed by colliding winds of O and Wolf-Rayet stars located in a massive stellar cluster.

Frequency Bands and RFI after this Year's World Radio Conference

Lunch Colloquium
Dr. Axel Jessner
ORATED
MPIfR

Radio astronomy requires wide frequency bands on pre-determined frequencies without detectable interference for many hours of observations. These requirements are non-negotiable,- they are determined by physics! At the same time, governments, industry and commerce see the radio spectrum primarily as a source of revenue,- far in excess of any funding that astronomy receives or even may receive in the future for its operation or instrumentation. The decision about the allocation and use of radio spectrum is the sovereign right of governments, but it is negotiated with stakeholders and internationally harmonised . Fortunately radio astronomy is recognised as an important stakeholder by the regulators and therefore consulted in all stages of the decision process. Final agreements have been made at the world radio conference in Geneva at the beginning of this year (WRC-12) and the talk will outline the process, the controversies and also the impact of the latest decisions from the radio astronomical point of view.

The first results of the Herschel-HIFI mission

Special Colloquium
Dr. Floris van der Tak
ORATED
SRON, The Netherlands

This talk reviews results from the first years of observations with the HIFI instrument onboard ESA’s Herschel space observatory. The talk starts by outlining the goals and possibilities of far-infrared and submillimeter astronomy, the limitations of the Earth’s atmosphere, and the scientific scope of the Herschel-HIFI mission. The presentation of science results from the mission follows the life cycle of gas in galaxies, emphasizing three themes: Structure of the interstellar medium, First steps in interstellar chemistry, and Formation of stars and planets. Special attention is given to the use of reactive ions and molecules to probe the physical conditions of regions with high densities and/or radiation fields. The HIFI observations paint a picture where the interstellar medium in galaxies has a mixed, rather than a layered structure; the same conclusion may hold for protoplanetary disks.

Gravitational lensing by black holes in alternative gravity theories

Special Colloquium
Prof. Laszlo Gergely
ORATED
Departments of Theoretical and Experimental Physics, University of Szeged, Hungary

Weak and strong gravitational lensing are powerful tools for studying the gravitational field created by black holes. I will present a series of results on light deflection and image formation by spherically symmetric black holes with (a) tidal charge, (b) in Horava-Lifsitz gravity and (c) in fourth order f(R) gravity. Beside interesting theoretical results, like the derivation of a critical behaviour, I will also emphasize the existence of observable signatures, which could disseminate between these black holes, in particular the power law dependence of the magnification factors on the separation of the images.

Narrow-Line Seyfert 1 Galaxies, a quarter century after their discovery

Lunch Colloquium
Dr. Stefanie Komossa
ORATED
MPIfR

Narrow-line Seyfert 1 galaxies (NLS1s) manifest one extreme form of Seyfert activity. They are active galaxies with the most narrow Balmer lines, strongest iron emission complexes, steepest X-ray spectra, highest high-energy variability, lowest black hole masses, highest accretion rates, and strong(est) gaseous outflows. As such, NLS1 galaxies likely hold important clues to the key parameters that drive nuclear activity. Their high accretion rates close to the Eddington rate provide new insight into accretion physics, their low black hole masses and perhaps young ages allow us to address issues of black hole growth and of galaxy - black hole co-evolution, and their intense optical Fe II emission places strong constraints on Fe II and perhaps metal formation models and the physical conditions in these emission-line clouds. I provide a short review of the properties of Narrow-line Seyfert 1 (NLS1) galaxies across the electromagnetic spectrum, and then focus on their radio properties, which have only recently been explored, leading to a number of interesting discoveries and surprises.

Status and first results of the SVLBI mission RadioAstron

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

The 10-meter space radio telescope Spektr-R was successfully launched on July 18, 2011, and unfurled several days later. The space element of the ground-space VLB interferometer RadioAstron covers four frequency bands from 92 to 1.3 cm and provides baselines up to 350,000 km. This will allow to study space objects with a resolution as high as about 10 microarcsecond. Current status of the mission and early results of RadioAstron SVLBI observations will be presented.

White dwarf binaries, mergers, and explosions

Main Colloquium
Prof. Marten van Kerkwijk
ORATED
University of Toronto, Canada

Stars in binaries often have much more exciting lives, deaths, and afterlives than single ones. I will review the especially varied possibilities involving white dwarfs, which include revival and total annihilation. The latter leads to so-called type Ia supernova explosions, for which empirical calibrations of their luminosities have allowed the measurement of the acceleration of the expansion of the Universe. The standard theoretical picture, in which unstable fusion is ignited in white dwarfs that approach or are made to exceed the largest possible (Chandrasekhar) mass, has a number of problems I will discuss these problems and will show that they would be resolved if instead, as I will propose, the ignition occurs more generally when two carbon-oxygen white dwarfs merge.

Self-annihilating dark matter: The gamma-ray to radio connection

Special Colloquium
Hannes-S. Zechlin
ORATED
University of Hamburg

Over the last decades, overwhelming evidence for the existence of a new, non-baryonic form of matter has emerged on both fundamental particle as well as cosmological scales. This so-called cold dark matter manifests itself as a new form of heavy, neutral particle very weakly interacting with standard model particles. Common models predict dark matter to be self-annihilating to standard model final states, eventually producing high-energy photons and charged leptons. In this talk, I will focus on the astrophysical imprints of dark matter and the corresponding observational efforts for its (indirect) detection. In particular manifesting itself in the gamma-ray band, cold dark matter may also be detectable in the X-ray and radio band via secondary inverse Compton and synchrotron emission of charged final-state leptons. Governed by the gamma-ray observations, I will show how these searches can be extended using observations in the radio band.

The Concentrations of Massive Galaxy Clusters

Lunch Colloquium
Dr. Aaron Ludlow
ORATED
AIfA

Recent large volume simulations of structure formation probe the high-mass end of the matter power spectrum with sufficient statistics to robustly measure the concentrations of the most massive and rarest collapsed structures at any time. A novel feature of the halo mass-concentration relationship has emerged from these studies: a flattening and subsequent increase in the mean halo concentration with increasing mass and redshift. I will show, using the Millennium series of N-body simulations, that this upturn arises as a result of a specific and transitory phase of halo accretion, which dominates the rarest objects at any given redshift and mass scale. These results may have implications for our understanding of selection biases in samples of strong lensing clusters, which appear to have denser cores than their siblings in simulations of the LCDM Universe.

A simple model for HI spectral line profiles

Lunch Colloquium
Dr. Ian Stewart
ORATED
AIfA

The HI spectral line at 21 cm contains a lot of information about the galaxy it originates from. Such items as mean velocity, total flux and velocity width are fairly obvious but one can also potentially extract information about the velocity dispersion due to thermal and turbulent effects and the spatial distribution of HI in the galaxy - even when the source is not spatially resolved. There are advantages to determining these things via fitting a parameterized model to the line profile. In this talk I present such a model, which has 6 free parameters, and show that it fits well to nearly all of the line profiles of the 34 THINGS galaxies (Walter et al 2008). I’ll explore various things one can do with such a model, including source detection, Tully-Fisher calculations, and finally an interesting way to extract group properties such as the mass function via a Bayesian stacking approach.

The Giant Metre-wave Radio Telescope: Current Status, Some Recent Science Highlights and Future Upgrade Plans

Main Colloquium
Prof. Yashwant Gupta
ORATED
National Centre for Radio Astrophysics, India

The Giant Metrewave Radio Telescope (GMRT), located near Pune, India, is today a major international facility for work in Radio Astronomy in the frequency range of 150 MHz to 1500 MHz. Consisting of 30 fully steerable antennas of 45 metre diameter each, it can be used as an aperture-synthesis array to produce maps of the radio brightness of extended sources, as well as a phased array with a highly directive beam to study compact radio sources. Each antenna is equipped with multi-frequency feeds and a low noise, high gain heterodyne receiver system, the signal from which is transmitted to a central station using optical fibres. At the central station, multi-purpose back end receivers to process and combine the signals from the 30 antenna stations include (i) a 256 spectral channel correlator and (ii) a phased array combiner followed by a high time resolution pulsar receiver. The sophisticated electronics is backed up with state of the art computing facilities, control and analysis software, to exploit the full capability and versatility of the GMRT. This talk will present an overview of the working of the GMRT. Many new and interesting science results in different areas have been produced using the GMRT since it was commissioned in 2002, and some of the major ones will be highlighted. Finally, plans and status of a major upgrade of the GMRT that is currently underway, will be described. This upgrade will significantly increase the scientific capabilities of the telescope, and keep it internationally competitive for several more years to come.

Orion BN/KL: A laboratory for high-mass star formation

Special Colloquium
Dr. Ciriaco Goddi
ORATED
ESO

The details of how massive stars form are poorly known. Orion BN/KL is the closest known region with ongoing massivei star formation, and hence offers unique chances for a detailed study and an excellent laboratory to test new theories. Despite being considered an archetype, it is still poorly understood. I will review recent work which has resolved long-standing debates on this enigmatic region. In particular, I will describe: 1) a beautiful example of disk-mediated accretion and (magnetic) outflow recollimation in a high-mass protostar; 2) a dynamical model to explain the famous “explosive” BN/KL flow; 3) a new hypothesis for the excitation of the Orion Hot Core. A better understanding of Orion BN/KL may permit to significantly advance our understanding of high-mass star formation.

UpGREAT: the extension of GREAT into heterodyne arrays for infrared spectroscopy with SOFIA.

Lunch Colloquium
Dr. Christophe Risacher
ORATED
MPIfR

In the millimeter and submillimeter domain, heterodyne receivers have played a major role in astrophysics as well as planetary remote sensing. It is the frequency range of interest for studying line radiation from cool gas and dust. Although continuum receivers in that frequency range routinely incorporate hundreds of pixels, the progress has been slower for heterodyne receivers. There are few small to mid-size arrays operating in the 80-950 GHz, but many telescopes are still operating single pixels receivers and almost none above the THz region. This talk presents the plan for two new heterodyne arrays (2x7 pixels and 7 pixels) for the frequency ranges 1.9-2.5 THz and 4.7 THz, targetting among other species the [CII], OH and [OI] lines. These arrays should start operation onboard the NASA-DLR airborne observatory SOFIA in 2014-2015.

Disk-Halo interaction: The molecular clouds in the Galactic Center Region

Main Colloquium
Dr. Denise Riquelme
ORATED
IRAM, Granada

From a large-scale study of the Galactic center (GC) region in SiO(2-1), HCO+(1-0), and H13CO+(1-0) (Riquelme et al 2010b, A&A, 523, A45) we identify shock regions traced by SiO. We selected 9 positions called by us as ”intersction regions”, because they mark the places where gas in the GC could be interacting with gas coming from higher latitude (”disk-halo interaction”) or from larger galactocewntric radius. These positions were studied using the 12C/13C isotopic ratio to trace gas accretion/ejection. We found a systematically higher 12C/13C isotopic ratio (> 40) toward the halo and the X1 orbits than for the GC ”standard” molecular clouds (20-25). The high isotopic ratios are consistent with the accretion of the gas from the halo and from the outskirts of the Galactic disk (Riquelme et al 2010a, A&A, 523, A51). We derive two kinetic temperature regimes (one warm at sim200 K and one cold at sim40 K) for all the positions, except for the halo where only the warm component is present. The fractional abundances derived from the different molecules support the shock origin of the heating mechanism in the GC.

The Origins of NRAO and the Evolution of Radio Astronomy into a Big Science

Special Colloquium
Dr. Ken Kellermann
ORATED
NRAO

By the early 1950s it had become apparent that the US was clearly lagging behind Australia and UK in the emerging field of radio astronomy. Sparked by the ambitions of Taffy Bowen in Australia, and fueled by cold war concerns of scientific, economic, political, and military competiveness, a few influential American scientists lobbied the newly formed National Science Foundation to develop a national radio astronomy observatory. But, rivalries between scientists on the east and west coasts, between radio and optical astronomers, and between proponents of big federal and small university facilities delayed progress for nearly three years. Although these rivalries continue to this day, through the perseverance and political perspicacity of its President, Lloyd Berkner, Associated Universities Inc. won the contract to build a national radio observatory and began the construction of a 140-ft radio telescope in Green Bank, West Virginia. However mismanagement by both AUI and a series of contractors led to the resignation of the first NRAOi director, Otto Struve, followed by AUI President Berkner himself. After nearly a decade the 140-ft telescope was finally completed at a cost which was way over budget, and which began a new era in which radio astronomy was transformed from a hands-on science by a small group of expert practitioners to a big science operation with ever decreasing involvement of individual scientists in the design, construction, operation, and eventually even the acquisition and analysis of data.

Testing gravity theories in radiative regime using pulsar timing array

Lunch Colloquium
Dr. Kejia Lee
ORATED
MPIfR

Millisecond pulsars (MSPs) can be used as very stable celestial clocks to probe the space-time in our Galaxy. A pulsar timing array project observing a sample of MSPs ( 20) at regular intervals is able to directly detect GWs, as well as measure the wave’s intrinsic properties. Independent of currently available tests, pulsar timing array experiments will enable interesting radiative tests of general relativity (GR). After reviewing the pulsar timing technique employed for detecting GWs, we will focus on two major tests of GR in the radiative regime: 1) the test for the polarization of GWs, and 2) the test for the dispersion of GWs. The methods for carrying out such tests will be discussed, as will the expected accuracy of these tests.

Supermassive binary black hole systems in active galaxies

Lunch Colloquium
Dr. Mar Mezcua
ORATED
MPIfR

It is widely accepted that galaxies are not isolated objects in the Universe, but are rather observed to undergo galaxy merging. If nearly all galaxies host a supermassive black hole in their center, it is expected that pairs of supermassive black holes will be formed in the course of a merger event. The detection and number estimates of binary black hole systems can, thus, help us to understand how galaxies form and grow, and shed light on the evolutionary models that rule the Universe. In this Colloquium I’ll present the results of my PhD thesis, which aims to pursue observational evidence for binary black hole systems. For this, I have analyzed three kinds of extragalactic objects: X-shaped radio galaxies, ultraluminous X-ray sources, and double nucleus galaxies. I will detail our observations and analyses of these systems and the conclusions obtained when combined all observational data.

Magnetic field structure in supernova remnant IC443

Lunch Colloquium
Dr. Talayeh Hezareh
ORATED
MPIfR

We study the structure of the magnetic field in a dense clump around the supernova remnant IC 443. This source is an interesting example of interaction between the shock wave driven by the supernova and the nearby molecular cloud. I will present the on-the-fly polarization maps of 12CO(2-1) in IC 443-G, the aforementioned dense clump around the SNR. We used XPOL, the correlation polarimeter at the IRAM 30-m telescope for this purpose, with the aim to detect the Goldreich-kylafis effect, i.e., linear polarization in the CO emission due to the presence of a magnetic field in an anisotropic radiation field.

Beyond classical black hole spacetimes

Special Colloquium
Dr. Piero Nicolini
ORATED
Institut für Theoretische Physik, Universität Frankfurt

In this talk we will pedagogically review some of the latest ideas about how general relativity can be improved in the extreme energy/small scale regime. Specifically we will address the repercussions of modified gravity theories on the physics of black holes in order to overcome usual inadequacies of the classical formalism. As a second point we will address the problem of astrophysical observations of non-classical effects. The main goal of the talk is to open an interdisciplinary discussion between the communities of astronomers and theoretical physicists.

Star Formation activities in the dark corner of Cygnus OB7

Lunch Colloquium
Dr. Tigran Khanzadyan
ORATED
MPIfR

One of the least studied regions in Cygnus is OB7 located at a distance of around 800 pc. The Cyg OB7 region contains several dark clouds which are collectively referred to as Kh 141 and individually identified with Lynds catalog numbers. The dark clouds of interest here are LDN1003/1004 which define the Braid Nebula Star Formation Region. First study of the LDN 1003 molecular cloud dates back to the discovery of a red nebulous object RNO 127 which eventually turned out to be an HH object. The consecutive studies of the region our team uncovered numerous H alpha stars, optical and near-infrared HH objects and reflection nebulae two of which, the Braid Nebula and HH 381 IRS nebula, were found to be associated with an FU Ori type eruptive variable star. These were signs of significant star formation activity which warranted a follow-up unbiased, wide-field and multi-waveband study of the region that our consortium is currently conducting.

The role of star formation and feedback in cosmological simulations of galaxy formation

Main Colloquium
Prof. Dr. Romain Teyssier
ORATED
University of Zürich

I will discuss results obtained by state-of-the-art cosmological simulations of galaxy formation. I will highlighti the important role played by feedback and star formation, both processes captured at the subgrid level. I will discuss the limitation of the current approach and present a few recent results that we obtained trying to overcome these limitations by resolving the interstellar turbulence. I will present new interesting results obtained with the RAMSES code for dwarf galaxies. I will also present simulations at galaxy cluster scale of massive elliptical, showing how the simulated galaxy properties depend critically on AGN feedback.

The possible double star cluster NGC 654/NGC 663

Lunch Colloquium
Dr. Michael Geffert
ORATED
AIfA

“Schülerlabor Küstner” is an ongoing project to motivate students from schools to participate in scientific projects during lab courses. One part of this project is the determination of proper motions based on the photographic plates taken by Küstner in Bonn 100 years ago. In this talk we will present the first results of two proper motion studies of the star clusters NGC 654 and NGC 663. For NGC 663 our study is the first investigation of its proper motions so far. Cluster parameters were derived using membership criteria based on proper motions. Since the two clusters are nearly at the same distance from the sun (2000 pc) and separated by a linear distance of about 25 pc we will also discuss the possibility that NGC 654 and NGC 663 is a binary cluster.

Detection and interpretation of AGN time delays in X-rays and very high energies

Special Colloquium
Dr. Dimitris Emmanoulopols
ORATED
University of Southampton

Detection of time delays in AGN light curves, obtained in different energy bands, can yield significant information about the physical properties of the observed sources, in X-rays, as well as the fundamental properties of vacuum, Lorenz invariance violations, in very high energies (VHE>100 GeV). I will be talking about these two genuinely different subjects mainly from the point of view of time-series analysis presenting you the latest results and interpretations. X-Rays:Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lag behind the corresponding hard band X-ray variations) in Seyfert galaxies, is one of the hottest topics in the field of AGN. The physical origin of these delays is greatly debated, as is the question of their ubiquity in accretion systems. I will present X-ray time lag analysis, as a function of Fourier frequency, for MCG-6-30-15 and Mrk 766 using long term XMM-Newton light curves together with some physical modelling of the corresponding time lag spectra. Both the time lag spectra of MCG-6-30-15 and Mrk 766 show negative values at high frequencies, favouring a reflection scenario from material situated very nearby to the central black hole. VHE:Einstein postulated that ”Light always propagates through a vacuum at a definite velocity, c, which is independent of the state of motion of the emitting body”. This is the framework of classical special relativity, having no fundamental length-scale associated with it (Lorentz invariance). However, quantum effects at the Planck scale, where gravity becomes a strong force, are expected (although not yet proven) to strongly affect the nature of space-time, causing violations of this invariance. It is believed that such violations can be tested by measuring time-lags between VHE, emitted simultaneously from distant astrophysical sources, expressing possible variations of photon speed as a function of energy. Since blazars are in relatively cosmological distances and emit variable emission in VHE they are considered ideal candidates to test such deviations. I will present the current results and future prospects.

Confronting Star-formation Models with Magnetic-field Observations

Special Colloquium
Dr. Hua-bai Li
ORATED
MPI for Astronomy

Self gravity, turbulence and magnetic fields (B-fields) certainly all play a role in the star-formation process, which transforms just a small fraction of the mass of molecular clouds into stars. How exactly these forces interact with each other to regulate star formation is, however, still highly controversial. I will report sub-mm/optical observations of B-fields, which can put constraints on the models of cloud formation, cloud fragmentation, cloud core formation, and ambipolar diffusion.

First application of a full photonic local oscillator to terahertz astronomy

Lunch Colloquium
Dr. Ivan Camara Mayorga
ORATED
MPIfR

This talk reports on our recent improvements in photomixing technology for the realization of a photonic local oscillator (LO) at 1.05 THz for the Atacama Pathfinder Experiment (APEX) radiotelescope in the Atacama desert, Chile. Experiments with state-of-the-art photomixers, operated at room temperature and in cryogenic environment demonstrate successful operation of an astronomical heterodyne receiver at 1050 GHz with a superconductor-insulator-superconductor (SIS) mixer. The system noise temperature of the heterodyne receiver was compared with results using a conventional solid-state LO in the same receiver system, revealing similar noise temperatures. An optical comb generator served as a relative frequency reference to which both lasers were phase-locked. Under the phase lock condition, the 3 dB linewidth of the THz signal was below 3 kHz and could be continuously tuned within a range of 500 MHz -the overall tunability of the system was determined by the photomixer antenna resonance bandwith, which was roughtly 200 GHz. We installed the laser system in the telescope pedestal, from there, the frequency-stabilized laser signal, was fed into the photomixer, installed in the Nasmyth cabin of the telescope, though a 20 meters long single-mode fiber optic.

The Dusty Heart of Active Galaxies - Dissecting the Torus with IR Observations

Special Colloquium
Sebastian F. Hönig
ORATED
MPIfR Bonn

Over the last years we have made significant progress in our understanding of the dusty environment around AGN – commonly referred to as “dust torus”, one of the cornerstones of AGN unification. A good part of this progress has been made possible by the high spatial resolution capabilities of the VLT and VLTI in the infrared. We are now able to not only resolve the torus but constrain the distribution of the material that is believed to eventually accrete onto the supermassive black hole. I will give an overview of some of our recent results involving small samples of AGN as well as individual objects using VISIR, MIDI, and the Keck interferometer together with 3D clumpy torus models.

Wanted: The best model for the distribution of free electrons in the Milky Way

Lunch Colloquium
Dr. Dominic Schnitzeler
ORATED
MPIfR

To map the structure of the large-scale magnetic field of the Milky Way, and also to combine pulsar signals that are emitted at different frequencies, one needs to know the column density of free electrons between the source of the emission and the observer. At least eight models have appeared in the literature that describe how these free electrons are distributed throughout the Milky Way, and we have quantitatively tested the accuracy of these models, using pulsars at known distances. We also included 2 new models that give a more pragmatic description of the free electron distribution. In my talk I will present a brief overview of the different available models, I will introduce the metric we devised to quantitatively compare their predictive quality, and I will show the results of our analysis.

Interstellar chemistry of nitrogen

Main Colloquium
Dr. Pierre Hily-Blant
ORATED
University Joseph Fourier, Grenoble

Nitrogen is among the six most abundant element in our Galaxy and it is a fundamental component of molecules associated with life. Nitrogen-bearing molecules are routinely observed towards a wide variety of physical and dynamical conditions in the Cold Neutral Medium. The list of interstellar N-bearing species detected since the discovery of the CN radical includes simple (2 atoms) to complex molecules with more than 10 atoms. The interstellar chemistry of nitrogen may be considered a simple one since it can be reduced to a relatively small number of reactions. However, observational constraints have emphasized several caveats of pure gas-phase model predictions. One is the long-lasting problem of the abundance of ammonia. But more recent Herschel observations with the HIFI instruments have revealed that the problem extends to the lighter hydrides NH and NH2. Indeed, other weaknesses of our understanding of the nitrogen chemistry have accumulated in the last decade. In addition, models of nitrogen fractionation under typical dark cloud conditions do not predict strong fractionation levels. This is consistent with some observations, but at odds with others. Nitrogen isotopic ratio 14N/15N is shown to vary strongly in the local interstellar medium, whether it is measured in the diffuse molecular gas or in denser objects including comets. In this talk, we will review general aspects of the nitrogen chemistry. In doing so, we will give particular emphasis to the rates of some key reactions for the production of nitrogen hydrides. We will discuss observations of the nitrogen isotopic fractionation, and recent observational results towards dark clouds will be presented.

Exploring the Dark Universe in the Radio

Lunch Colloquium
Dr. Andrei Lobanov
ORATED
MPIfR

Addressing the questions of the nature of dark matter and dark energy and the new physics beyond the standard model defines the most fundamental frontier in the modern physical research. Predicted in many extensions of the standard model of particle physics, weakly interacting sub-eV particles (WISP), and axions and hidden photons in particular, are recognized as strongly motivated candidates for the dark matter and dark energy particles. While sub-eV WISP cannot be detected in accelerator experiments, searches for these particles can be done most efficiently with low-energy laboratory experiments using lasers and microwave cavities and with astrophysical measurements in the radio through gamma-ray bands. The radio regime is exceptionally well suited for detecting the electromagnetic signature of the photon-photon and axion-photon oscillations, extending down to  10-19 eV the range of the hidden photon mass probed, and closing the last gaps in the strongly favoured 1-5 micro-eV range for the axion mass. This talk will focus on giving a summary of our recent results in these fields and describing a new research program that would combine radio astronomical measurements at the Effelsberg 100-meter telescope and microwave cavity experiments using the DESY HERA accelerator facilities. This research program would expand by  5 orders of magnitude the range of photon mass probed, bring the most stringent constraints on the axion coupling constant in the 1-2 micro-eV and 3-5 micro-eV axion mass ranges, and provide a broad, fundamental theoretical basis for interpreting and expanding the experimental work both in the laboratory and with astronomical measurements.

Runaway massive stars from R136

Lunch Colloquium
Dr. Sambaran Banerjee
ORATED
AIfA

We conduct a theoretical study on the ejection of runaway massive stars from R136 — the central massive, star-burst cluster in the 30 Doradus complex of the Large Magellanic Cloud. Specifically, we investigate the possibility of the very massive star (VMS) VFTS 682 being a runaway member of R136. Recent observations of the above VMS, by virtue of its isolated location and its moderate peculiar motion, have raised the fundamental question whether isolated massive star formation is indeed possible. We perform the first realistic N-body computations of fully mass-segregated R136-type star clusters in which all the massive stars are in primordial binary systems. These calculations confirm that the dynamical ejection of a VMS from a R136-like cluster, with kinematic properties similar to those of VFTS 682, is common. Hence the conjecture of isolated massive star formation is unnecessary to account for this VMS. We further note that during the clusters’ evolution, mergers of massive binaries produce a few single stars retaining per cluster, within 2 Myr age, with masses significantly exceeding the canonical upper-limit of 150 M_odot. The observations of such single super-canonical stars in R136, therefore, do not imply an IMF with an upper limit greatly exceeding the accepted canonical 150 M_odot limit, as has been suggested recently (Crowther et al., 2010), and they are consistent with the canonical upper limit.

The globular cluster/central black hole connection in late-type spiral galaxies

Lunch Colloquium
Prof. Rosa Gonzalez-Lopezlira
ORATED
AIfA

We investigate the correlation between total number of globular clusters and black hole mass in a sample of late-type spiral galaxies. We find a linear relation is indeed in place. Interestingly, if the “deviant” lenticular galaxies in the sample of elliptical and S0 galaxies of Harris & Harris (2010) are included in the fit, the slope approaches unity, i.e., the relation becomes virtually parallel to the trend set by elliptical galaxies, and tighter than before. The zero-point of this relation implies that, compared to elliptical galaxies, late-type spirals and these lenticular galaxies have black holes that are about 10 times lighter for the same number of globular clusters, in resemblance to what has been found before from the correlations between black hole mass and bulge mass, and between black hole mass and bulge stellar velocity dispersion. There seem to exist two different black hole feeding modes, and we speculate whether the deviant lenticulars have not had time to establish the most efficient one after a recent merger.

The early evolution of protostellar disks: fragmentation, episodic accretion, planet formation and other unexpected effects

Main Colloquium
Dr. Eduard Vorobyov
ORATED
Institute of Astronomy, University of Vienna

I will review the recent progress in our understanding of the early stages of protostellar disk evolution when the disk is deeply embedded in the parent core. In this stage, disks are often prone to gravitational instability and fragmentation, which lead to a zoo of various effects, the importance of which has not been appreciated until recently. I will demonstrate how disk fragmentation can trigger episodic accretion onto the star, an effect having far-stretching consequences for the evolution of pre-main-sequence objects. Formation of gas giants and brown dwarfs on wide orbits and ejection of brown dwarfs and very-low-mass stars into the intracluster medium can also be triggered by disk fragmentation. Other direct outcomes of disk fragmentation include the flattening of the mass accretion – stellar mass relation and the crystallization of amorphous silicates in the depths of massive fragments. Finally, I will show how episodic accretion can resolve the long standing luminosity problem, whereby young stars are systematically underluminous compared to what standard theories of star formation predict.

High-resolution wideband spectrometers for radio astronomy: Fast Fourier Transform Spectrometer (FFTS)

Lunch Colloquium
Prof. Dr. Bernd Klein
ORATED
MPIfR

I will review the developments of our digital wideband Fast Fourier Transform Spectrometers (FFTS).In just a few years, FFTS back-ends have become a new standard for heterodyne receivers, particularly in the mm and sub-mm wavelength range. They offer high instantaneous bandwidths with many thousands spectral channels on a small electronic board. Our FFT spectrometers make use of the latest versions of GHz analog-to-digital converters (ADCs) and the most complex field programmable gate array (FPGA) chips commercially available today. The XFFTS is our latest development step: The new spectrometer board is able to analyze 2.5 GHz of instantaneous bandwidth with up to 65536 (64k) spectral channels. An early version of the XFFTS with 32k channels is in successful operation at APEX and SOFIA since 2010/11. Finally, I will give an outlook of upcoming FFTS developments.

Preparation to the Planck data analysis: modeling of the polarized Galactic emissions

Special Colloquium
Dr. Lauranne Fauvet
ORATED
ESA Leiden

The PLANCK satellite is an ESA mission, launched the 14th of May 2009. It is providing measurement of the CMB anisotropies, both in temperature and polarization over the full-sky with an unprecedented accuracy. These measurement will allow us to constrain the cosmological parameters describing the dynamic and content of the Universe. In particular the study of the BB modes could give an access to information regarding the inflation period. This level of accuracy will be reachable in function of our ability to minimize the signal contamination due to Galactic polarized foregrounds. In this context we have developed and implemented a 3-D joint model of the two main polarized Galactic diffuse emissions: synchrotron and thermal dust emissions. We constrained the parameters of this model by comparison with the preexisting data from WMAP, Archeops and the 408 MHz all-sky continuum survey. We where then able to estimate the bias due to these foreground emission on the angular power spectra of the primordial BB modes. PLANCK covers a large range of frequencies from 25 GHz to 1 THz and therefore is able to give a measurement of the foreground emissions. In particular, because of its 7 polarized channels it will for the first time allow the simultaneous precise measurement of the main polarized Galactic emissions: synchrotron and thermal dust. We then explored the ability to constrain the Galactic magnetic field intensity and spatial distribution with the incoming data from the PLANCK satellite experiment.

The origin of OB runaways stars

Main Colloquium
Prof. Dr. Simon Portegies-Zwart
ORATED
Sterrewacht Leiden, Leiden University

More than 20% of all massive stars in the Milky-way Galaxy have an unusual high velocity of >30km/s. The origin of this population of runaway OB stars has been puzzling astronomers for more than half a century. In one of the favorite explanations a star is launched from a binary system when its companion explodes in a core-collapse supernova. This mechanism fails to explain the high proportion of runaway stars that ware ejected from clusters, because the ejection occurred well before any star experienced a supernova explosion. We demonstrate that the observed runaways are explained by stellar ejections mediated by strong three-body interactions with a binary star. Such a binary forms during the core collapse of a young (aplt 1Myr) and rather low mass ( 5000-10000) star cluster. This model reproduces the key characteristics of OB runaways in the Milky-way Galaxy and it explains the apgt 100 runaway stars around young star clusters, e.g. R136 and Westerlund 2. The high proportion and the distribution in mass of OB runaway stars in the Milky-way Galaxy can be explained if the vast majority of massive stars are born in dense and relatively low mass clusters.

Magnetic Fields and Gas Flows around Circumnuclear Starbursts

Lunch Colloquium
Dr. Rainer Beck
ORATED
MPIfR

Radio continuum observations of galaxies revealed strong and turbulent magnetic fields in the circumnuclear starbursts of up to 100 MicroGauss strength. Such fields are dynamically important and give rise to magnetic stresses which cause inflow of gas towards the center. This may solve the long-standing question of how to feed active nuclei. Galaxies with little star-formation activity in the central region host weaker and partly regular magnetic fields. -- Strong magnetic fields were also measured in the central outflow cone of the starburst galaxy NGC253. Faraday rotation data indicate a large-scale helical field which may collimate the outflow, possibly related to the "Fermi Bubbles" of the Galactic Center.

An SZ take on Galaxy Cluster Radio Halos

Lunch Colloquium
Dr. Kaustuv moni Basu
ORATED
AIfA

Giant radio halos in galaxy clusters provide the best evidence that ultra-relativistic particles (i.e. cosmic rays) and magnetic fields exist over Mpc scales. Despite their importance for understanding cluster growth through mergers, the powering mechanism of these objects remains uncertain. Traditionally, the theoretical models of radio halo origin have depended on the observed correlation of cluster radio and X-ray properties, where X-ray luminosities are used to measure the cluster mass. I will show what happens when cluster masses are measured using the Sunyaev-Zel’dovich (SZ) effect instead, which delivers a more unbiased mass estimate from the total integrated pressure of the intra-cluster gas.