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Universität zu Köln
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Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

Program

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The program can be found as a PDF file here.

 

Invited speakers

Santiago G. Burillo
Observatorio Astronómico Nacional, Alcalá de Henares, Spain

The Footprints of AGN Feeding and Feedback in low-L AGNs The study of the content, distribution and kinematics of interstellar gas is a key to understand the fueling of AGN and star formation activity in galaxy disks. Current mm-interferometers provide a sharp view of the distribution and kinematics of molecular gas in the circumnuclear disks of galaxies through extensive CO line mapping. On the other hand, the use of specific molecular tracers specific to the dense gas phase can probe the feedback influence of activity on the chemistry and energy balance/redistribution in the interstellar medium of galaxies. Radiative and mechanical feedback is often invoked as a mechanism of self-regulation in galaxy evolution. A detailed study of nearby AGNs is essential if we are to understand if and how accretion can self-regulate. We used the high-resolution (<1") interferometer CO maps obtained with the IRAM array in the context of the NUclei of GAlaxies (NUGA) survey to study the mechanisms responsible to fuel AGN and Star Formation activity in the central R<1 kpc disks of a sample of 25 active galaxies at 10-100 pc scale. More recently we have used the ALMA interferometer to image the distribution of molecular gas in the circumnuclear disks of a subset of nearby Seyferts. In two of these sources, NGC1068 and NGC1433, we report the discovery of two massive molecular outflows.

Ross Church
Dep. of Astronomy & Theoretical Physics, Lund Observatory, Sweden

Stellar Collisions at the Galactic Centre Observations of the stars at the Galactic Centre show that there is a lack of red giants within about 0.5 pc of the super-massive black hole. The very high stellar number densities this close to the SMBH imply that the giants -- or their progenitors -- may have been destroyed by stellar collisions. I will review the expected rates of collisions between different types of stars at the Galactic Centre and their likely effects, and attempt to quantify how large a contribution stellar collisions could make to the puzzle of the missing red giants.

Roland M. Crocker
Max-Planck-Institute für Kernphysik, Heidelberg, Germany

The Giant Magnetized Outflows from the Galactic Centre Radio polarization observations by the Parkes radio telescope in Australia have recently led to the discovery of giant radio lobes emanating from the Galactic nucleus. These lobes are largely coincident with the Fermi Bubbles discovered in gamma-ray data but actually extend to even larger angular scales, ~55-60 degrees north and south of the Galactic plane. The lobes extend more than half way across the sky as seen from Australia. I will explain why we believe the radio lobes -- and the Fermi Bubbles -- are likely the result of the concentrated star formation occurring in the Central Molecular Zone rather than signatures of putative activity of the super-massive black hole. In fact, I will argue that these giant outflow phenomena are consequences of processes that tend to keep the black hole rather quiescent.

Michael Kramer
Max-Planck-Institut für Radioastronomie, Bonn, Germany

The Galactic Center Black Hole Laboratory The Galactic Center is the closest super-massive black hole near Earth and hence offers us the opportunity to study gravity under extreme conditions. One way of achieving this is to find pulsars orbiting Sgr A* which would allow us to measure the spin and quadrupole moment of the central black hole with superb precision. The prospects and implications for tests of theories of gravity are discussed and the needed experiment explained. The required search for pulsars in the centre reason is difficult but received an unexpected boost by the recent discovery of radio pulsations from a magnetar with the Effelsberg telescope as presented by Eatough et al. during this conference.

Carole Mundell
Liverpool John Moores University, Liverpool, United Kingdom

Black-hole fuelling, feedback and duty cycles The distribution of gas and stars in nearby galaxies traced by 3-D studies of molecular, neutral and ionised gas provide a unique view of the role of the multi-phase medium in triggering and fuelling nuclear activity in galactic nuclei on size scales ever closer to the central black hole. Although technically challenging such studies are now evolving to include comparative study of gaseous and stellar dynamics in active and quiescent galaxies. I will review 3D studies at optical, radio and mm wavelengths and highlight the importance of studying the inner kiloparsec, where activity and dynamical timescales become comparable, including a new IFU-imaging spectroscopic comparative study of the distribution and kinematics of ionised gas in a carefully matched sample of Seyfert and quiescent galaxies, selected from the SDSS, that takes 3D studies to higher redshift. I will show that variability in nearby radio-quiet AGN may provide parallels to our own Galactic Centre and that AGN duty cycles may be shorter than previously thought.

Delphine Porquet
University of Strasbourg, France

X-ray properties of the Galactic center I will review the present knowledge about the X-ray properties of the Galactic center that is one of the most richest regions of the sky hosting numerous astrophysical objects such as stars, X-ray binaries, supernovae remnants, non-thermal filaments, molecular clouds and last but not least the closest supermassive black hole. Sgr A* with a mass of about 4 millions solar masses is extremely faint, though a level of activity has been revealed through the detection of flares. Therefore, SgrA* is the ideal target to investigate the accretion and ejection physics in the case of extremely low accretion rate onto a supermassive black hole where black holes are thought to spend most of their lifetime, its impact on its neighborhood, and its history over cosmic time.

Lorant Sjouwerman
National Radio Astronomy Observatory (Socorro), USA

Monitoring observations of the interaction between Sgr A* and G2 with the Karl G. Jansky Very Large Array We report on an ongoing community service observing program to follow the expected encounter of the G2 cloud with the black hole Sgr A* in 2013. The NRAO Karl G. Jansky Very Large Array (VLA) has been observing the Sgr A region since 2012 October on roughly a bi-monthly interval, each for two hours, cycling through eight observing bands at their default continuum frequencies, using 2 GHz of bandwidth. We will discuss the strengths and weaknesses of observing with the VLA, the data reduction, and the latest results. The data from the monitoring program are publicly available through the NRAO data archive immediately after observing has completed, and the flux densities are published by NRAO staff as soon as the data are reduced. The cumulative results of the monitoring effort are posted on the service observing web page https://science.nrao.edu/science/service-observing.

Farhad Yusef Zadeh
Northwestern University, Chicago, USA

Star Formation Activity in the Galactic Center Infrared observations have shown the evidence that massive stars were formed in the hostile environment of Sgr A* a few million years ago. I will present VLA, ALMA and CARMA measurements suggesting that on-going star formation is still taking place in this region in the last few times 10^5 years. I will then discuss how stars are formed near Sgr A* in the context of the passage of a giant molecular cloud interacting with Sgr A*. A fraction of the material associated with the gaseous disk that forms stars may accrete onto Sgr A*. The high accretion rate may be responsible for the origin of the gamma-ray Fermi bubbles. If time permitting, I will discuss star formation on a large scale by showing the KS scaling relation in the CMZ and compare it with that of molecular clouds in the Milky Way and external galaxies.