Jan 28

"Multiwavelength Insights into the Nature of Weak Emission-Line Quasars at High Redshift"
Ohad Shemmer, University of North Texas

The Sloan Digital Sky Survey has recently discovered ~60 quasars at z=2.7-5.9 with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). I will present multiwavelength spectroscopic observations that provided insights into the nature of these remarkable sources. I will show that WLQs are unlikely to be dust-obscured quasars, broad-absorption line quasars, or high-redshift galaxies with apparent quasar-like luminosities due to gravitational lensing amplification. Additional monitoring data suggests that the weakness of the lines in WLQs cannot be explained by microlensing that amplifies the continuum relative to the emission lines in ordinary quasars. I will also argue against the idea that WLQs are the long-sought high-redshift BL Lacertae objects. Instead, I suggest that WLQs are quasars with extremely high accretion rates that suppress the formation of the high-ionization emission lines. Finally, I will discuss X-ray and near-infrared observations required to test this scenario with implications for emission line formation and the accretion process in active galactic nuclei.

Feb 11

"The Evolution of Quiescent Galaxies and the Morphology-Density Relation"
Arjen van der Wel, Max Planck Institute for Astronomy, Heidelberg, Germany

In this talk I will discuss some new answers to old questions about early-type galaxies. After setting the stage by describing some general features of the galaxy population as a whole, I will address a number of topics related to early-type galaxies, both in the present-day universe and at high redshift. These include their global properties in the present-day universe, their structural evolution with cosmic time, the importance of merging as a formation process, and the role of the environment. A picture will emerge which describes in broad strokes the origin of some fundamental features of the early-type galaxy population, in particular the morphology-density relation.

Apr 08

"Binary Super Massive Black Holes are Very Short-Lived"
Remco Van den Bosch, University of Texas at Austin

The merger time-scale of a super massive black hole is an open question. Observations and galaxy assembly simulations indicate that they must be very short-lived. Yet current theory cannot explain why the time scale is very short, especially in galaxies without gas. Using orbit-based models, I will show that interactions with individual stars will and can make the black holes merge on short time scales.

Apr 08

"The Nature and Origin of the Black Hole/Bulge M-L and M-sigma Relationships"
Martin Gaskell, University of Texas at Austin

Improved AGN black hole mass measurements show that there is a strong decrease in scatter in the relationship between black hole mass and bulge luminosity with increasing luminosity and very little scatter for the most luminous galaxies. It is argued that this is a natural consequence of the substantial initial dispersion in the ratio of black hole mass to total stellar mass and of subsequent galaxy growth through hierarchical mergers. 'Fine-tuning' through feedback between black hole growth and bulge growth seems neither necessary nor desirable.

Apr 15

"Studying Black Hole Growth in the Local Universe"
Andreas Schulze, AIP - Astrophysical Institute Potsdam

Supermassive black hole growth mainly occurs during bright QSO phases. Therefore a complete census of the active black hole population and its properties is required to understand black hole growth and its connection to galaxy formation. I will present results for a well defined local (z < 0.3) broad line AGN sample from the Hamburg/ESO Survey. I estimated black hole masses and Eddington ratios for this sample. I will present the results of a maximum likelihood approach to estimate the intrinsic distribution functions of black hole masses and Eddington ratios simultaneously in an unbiased way, taking the sample selection function fully into account. I will show an estimate of the fraction of active black holes, i.e. an estimate of the AGN duty cycle, showing a strong decrease with increasing black hole mass. I will argue that this supports the notion of anti-hierarchical growth of black holes.

Apr 22

"Electromagnetic Signatures of Black Hole Mergers"
Jeremy Schnittman, Johns Hopkins University

During the final moments of a binary black hole (BH) merger, the gravitational wave (GW) flux emitted from the system is greater than the combined electromagnetic luminosity of the entire observable universe. However, the extremely weak coupling between GWs and ordinary matter makes these waves very difficult to detect directly. Fortunately, the inspiraling BH system will interact strongly--on a purely Newtonian level--with any surrounding material in the host galaxy, and this matter can in turn produce unique electromagnetic signals detectable at Earth. The nature of these signals varies widely, from the impressions left on stellar density distributions, to the production of runaway quasars that escape from the galactic center at speeds of thousands of km/s, to the generation of ultra-relativistic shock-waves in magnetized accretion flows. I will describe a number of these different signatures, and discuss their expected event rates and potentials for positive identification, even before direct GW detectors like LISA are operational.

May 06

"The ATLAS3D Project: Towards a Paradigm Shift for Early-Type Galaxies"
Eric Emsellem, European Southern Observatory, Garching, Germany

Recent observations of nearby early-type galaxies has revealed a wealth of dynamical structures, associated with complex formation and evolution processes. Early-type galaxies seem to come in two broad flavours, slow- and fast-rotators, the former tending to be more massive and often having kinematically distinct cores and/or velocity twists, the latter exhibiting regular kinematics consistent with disk-like systems with (or without) bars.

An important step has now been taken with the ambitious ATLAS3D project: it probes a complete, volume limited (D < 41 Mpc), sample of 260 nearby early-type galaxies, and combines a unique observational dataset including multi-band photometry, integral-field spectroscopy, radio and millimeter observations with state-of-the-art numerical simulations and modelling efforts. I will present the main results from ATLAS3D, and try to cover what we have learned from the dynamical status, stellar populations and star formation history, role of the environment, molecular, neutral and ionised gas content, dark matter component, further lifting the veil on the true complexity of early-type galaxies and their origin.