Excellence Cluster Area F Science Meeting

Tuesday 16 Oct 2007, 09:00 → 20:30 Europe/Berlin

new seminar room (Max-Planck-Institut für extraterrestrische Physik (MPE))

Günther Hasinger (Max-Planck-Institut für extraterrestrische Physik)

agenda EXC_AreaF_Meeting_Oct16_schedule.pdf

09:00 → 09:15 Introduction

09:15 → 09:45 A sharp look into the Galactic Centre: Where we are and where we go

High angular resolution adaptive optics imaging and spectroscopy have shown beyond any reasonable doubt that the Galactic Center harbors a supermassive black hole. We have been able to determine the three dimensional orbits of stars within the central light days, and the flaring activity from the black hole gives first insights to the physical processes close to the last stable orbit. The Galactic Center constitutes the best astrophysical evidence for the existence of black holes, and it is the ideal laboratory for studying physics in the vicinity of such objects. Here we give an update on the latest results, and outline the next steps towards even higher angular resolution with infrared interferometry and extremely large telescopes. These experiments - and most notably the planned GRAVITY experiment for the VLTI - give promise to directly probe the physics and space-time curvature just outside the event horizon.

Speaker: Frank Eisenhauer (MPE)

Slides Eisenhauer_MPE.pdf

09:15 → 11:30 Local supermassive black holes

09:45 → 10:15 The supermassive black hole and central blue cluster in the Andromeda galaxy (M31)

I will discuss the dynamical structure of the M31 nucleus and present the evidence that it hosts a 100 million solar mass black hole. The black hole is surrounded by a disk of blue stars. Based on recent imaging with the Hubble Space Telescope imaging I discuss the origin and nature of this disk.

Speaker: Ralf Bender (MPE/USM)

Slides Bender_MPE+USM.pdf

10:15 → 10:30 Coffee break

10:30 → 11:00 X-ray morphology of M87

The X-ray morphology of M87 shows unambiguous signs of the SMBH strong impact on the thermal gas: cavities filled with relativistic plasma and quasi- spherical shocks. Using a simple hydrodynamic model of the gas surrounding M87 we derive the energy of the outburst, responsible for the shock, its age and duration. We show that the deposited energy of the outbursts is comparable to that radiated by M87's cooling atmosphere. We then compare gravitational potential profiles of M87 derived from X- ray and optical data. This comparison provides an independent method to measure the magnitude of non-thermal pressure (cosmic rays, magnetic fields and micro-turbulence) in the X-ray emitting gas.

Speaker: Eugene Churazov (MPA)

Slides Churazov_MPA.pdf

11:00 → 11:30 A search for supermassive black holes in pseudo- and low-mass bulge galaxies

Over the past decade we have learned that probably all ellipticals and bulges contain central supermassive black holes (SMBHs). The mass of the SMBH correlates both with the mass of the bulge component (about 0.15% of the bulge mass found in the SMBH) and with the velocity dispersion of the bulge. We are investigating whether these relations remain valid or how they change when galaxies with pseudobulges, very low-mass bulges or bulgeless galaxies are considered. Studying SMBH relations for both classical and pseudo-bulges reveals the importance of different growing mechanisms (mergers vs. secular evolution). We discuss the first results of our spectroscopic survey with Adaptice Optics SINFONI instrument at the VLT.

Speaker: Roberto Saglia (MPE)

Slides Saglia_MPE.pdf

11:30 → 12:30 Deep surveys

11:30 → 12:00 Evolution of black hole obscuration

I will review the deep and wide surveys in the 2-10 keV band with particular emphasis on the dependence of the fraction of absorbed versus unabsorbed AGN on luminosity and redshift. A strong dependence of this ratio with luminosity is found, clearly indicating the need to revise the strong version of the unified AGN picture. The dependence of absorption with redshift is more delicate and requires a good treatment of systematic selection effects. In the end these new findings are discussed in the context of the ‘downsizing’ evolution of AGN and the relation to their host galaxies.

Speaker: Guenther Hasinger (MPE)

Slides Hasinger_MPE.pdf

12:00 → 12:30 Dust and gas obscuration in AGN: new results from the XMM-COSMOS survey

We will present the results of a detailed X-ray spectral analysis on a sample ~1000 AGN selected from the XMM-COSMOS survey with a reliable spectroscopic or photometric redshift. We will discuss the general spectral properties of the sample (NH distribution, Gamma as a function of redshift or luminosity) and of interesting sub-classes of objects (QSO-2, C-thick candidates). We finally discuss the gas-to-dust ratio measures of the obscuring matter in the circumnuclear region. To this purpouse we have combined the gas column densities (NH) measured from the X-ray spectral analysis with the reddening estimates obtained from the Halpha/Hbeta lines ratio (0.1 < z < 0.5).

Speaker: Vincenzo Mainieri (ESO)

Slides Mainieri_ESO.pdf

12:30 → 13:30 Lunch buffet

13:30 → 15:45 Active galaxies

13:30 → 14:00 Resolving the central region of active galaxies with ALMA

Wide observational evidences suggest that the formation of a supermassive black hole (SMBH), a bulge and an active galaxy (and a QSO) are phenomena closely related to each other. However theoretically, these phenomena are far from being understood. In particular the main physical mechanisms storing very large amount of gas in the innermost galactic regions on timescales of several hundred million years are still a puzzle. Many theoretical studies suggest that gas accretion processes play an important if not the dominant role in the formation of a SMBH and its growth. Observationally the way to pursue is the direct detection of the gas and its properties in the inner region of active galactic nuclei. In this talk I demonstrate the high sensitivity and high spatial resolution of observations that the ALMA array will achieve. This will cast light on the key physical conditions that allow the rapid growth of SMBHs, its feeding during its lifetime, its relation to the star formation in spheroids and the appearance of QSOs at any redshift.

Speaker: Paola Andreani (ESO)

Slides Andreani_ESO.pdf

14:00 → 14:30 X-ray probes to the innermost part of active galactic nuclei

Various pieces of evidence suggest that X-ray emission from active galactic nuclei originates from the innermost part of the accretion disk around a central black hole. Strong gravity, which is expected to operate in the region in the vicinity of the black hole, could therefore have influences on the X-ray emission emerging from there. Under a certain paradigm, X-ray observations can potentially reveal the geometry of the accretion disk (and the X-ray source), the spin of the black hole, orbital motion of a hot spot, etc. through a spectroscopic study. The present status on these topics will be summarized.

Speaker: Kazushi Iwasawa (MPE)

Slides Iwasawa_MPE.pdf

14:30 → 14:45 Coffee break

14:45 → 15:15 Connecting star formation and AGN activity with galaxy interactions

In nearby galaxies, a strong connection between galaxy interactions and enhanced star formation (SF) has been observed. We demonstrate this connection by analyzing SDSS survey data using a variety of different statistics. In particular, we show that the specific SF rates of galaxies are higher if they have close neighbours. If we apply exactly the same techniques to AGN in the survey, we fail to uncover any evidence that enhanced nuclear activity is connected with galaxy interactions. AGN with close neighbours exhibit an enhancement in SF in exactly the same way as do star-forming galaxies with close neighbours. However, the accretion rate onto the black hole, as estimated from the extinction corrected [O III] luminosity, is not influenced by the presence or absence of a close companion. We know from previous work (Kauffmann et al. 2003) that galaxies with more strongly accreting black holes have experienced a larger amount of recent SF. This leads us to the conclusion that SF enhancement due to a close companion and SF enhancement due to an accreting black hole are two separate and distinct events. These two events may be part of the same physical process such as a merger, provided they are separated in time. In this case, accretion onto the black hole and its associated SF would occur only after the two interacting galaxies had already merged. The major caveat in this work is our assumption that the extinction-corrected [O III] luminosity is a robust indicator of the bolometric luminosity of the central black hole. It is thus important to check the results presented in this paper using indicators of AGN activity available at other wavelengths.

Speaker: Cheng Li (MPA)

Slides Li_MPA.pdf

15:15 → 15:45 Cosmological growth of SMBHs: constraints on kinetic and radiative feedback

The growth of supermassive black holes (SMBH) through accretion is accompanied by the release of enormous amounts of energy which can either be radiated away, as happens in quasars, advected into the black hole, or disposed of in kinetic form through powerful jets, as is observed in radio galaxies. Mechanical feedback from growing BHs is most likely responsible for the heating of baryons within the deepest dark matter potential wells at low redshift, thus regulating both cooling flows in galaxy clusters and the observed sizes and colors of the most massive galaxies. However, the kinetic luminosity of an AGN is very difficult to estimate reliably. Only recently have deep X- ray exposures of nearby ellipticals and clusters allowed the first direct estimates of AGN kinetic luminosities by studying the cavities, bubbles and weak shocks generated by the radio emitting jets in the intra-cluster medium. I will discuss a new reliable and simple estimator of the kinetic power of growing SMBH in the so- called "radio mode". From such a study, the kinetic luminosity function for radio jets, and their total integrated power in the local universe can be derived. Constraints on the redshift evolution of the AGN kinetic feedback will be discussed and compared with the radiative output of the evolving SMBH population, thus providing a robust physical framework for phenomenological models of AGN feedback within structure formation.

Speaker: Andrea Merloni (MPE)

Slides Merloni_MPE.pdf

15:45 → 16:15 Detection of supernova neutrinos in LENA

The measurement of supernova neutrinos with sufficient statistics can reveal details about the mechanism of gravitational collapses. With the planned 50kt liquid scintillator observatory LENA (Low Energy Neutrino Astronomy) about 20,000 neutrino events from a supernova type II in the galactic center could be observed. In six different reaction channels the total flux as well as the energy spectra of different neutrino flavors could be measured. In addition valuable information about neutrino oscillation parameters could be found. Our universe should be filled by diffuse background neutrinos from former supernovae explosions. It is the aim of LENA to perform for the 1st time a measurement of these background neutrinos. The amplitude and the spectral shape could yield information about models of gravitational collapses and on star formation in the universe.

Speaker: Lothar Oberauer (TUM)

Slides Oberauer_TUM.pdf

15:45 → 17:00 Stellar explosions and supernovae

16:15 → 16:30 Coffee break

16:30 → 17:00 Supernovae and black holes

The creation of stellar mass black holes is the predicted outcome of supernova explosions. Yet, no direct observations of such black holes emerging from supernovae have been obtained. I will discuss the different signatures of black hole formation in supernova explosions.

Speaker: Bruno Leibundgut (ESO)

Slides Leibundgut_ESO.pdf

17:00 → 17:30 Detectors

17:00 → 17:30 X-ray astronomy with eROSITA

This talk deals with the Spectrum-RG mission in general and the eROSITA instrument in particular. A medium size satellite called "Spectrum-Roentgen- Gamma" (Spectrum-RG or SRG) will be launched in 2011 into a 600 km orbit from Baikonur. The payload includes eROSITA (extended ROentgen Survey with an Imaging Telescope Array, MPE-led consortium, Germany) with 7 Wolter-type modules, the wide field X- ray monitor Lobster (LU, UK), and the high energy telescope ART ("Astronomical Roentgen Telescope", IKI, Russia). The eROSITA mission will conduct the first all-sky survey with an imaging telescope in the 2- 12 keV band with the main goal to detect 100 thousand clusters of galaxies and thereafter to do follow-up pointed observations of selected sources, in order to investigate the nature of Dark Matter and Dark Energy. But also the old ABRIXAS goal is maintained, namely to discover the hidden population of several hundred thousand obscured supermassive black holes and the first all-sky imaging X-ray time variability survey.

Speaker: Peter Predehl (MPE)

Slides Predehl_MPE.pdf

17:30 → 18:00 Discussion

18:30 → 20:30 Dinner at Buergerstuben, Garching