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Institute for the Physics and Mathematics of the UniverseWPI

1 Feb (Fri), pm 2:00

Place: Room 633, 6th floor, Research Centers Building, Kashiwa Campus Two speakers will give their talks in a successional way, with a possible break (30 min or so) between the two.
Speaker 1: Jenny Greene (Princeton Univ.)
Title: "The Mass Function of Local Active Black Holes"
Abstract: While black holes (BHs) are apparently a ubiquitous component of the nuclei of local spheroids, their role in galaxy evolution remains largely unknown. The tight correlations between galaxy spheroid properties and BH mass provide an important boundary condition for models of the coevolution of BHs and galaxies. I consider another important boundary condition: the local mass function of broad-line active galaxies. I present the distribution of BH masses and accretion rates for active galaxies in the local universe, and compare them to the distributions in both inactive and narrow-line AGNs. In particular, I focus on the host galaxies and space densities of BHs with masses < 10^6 M_sun, in the hopes of learning something about the mass spectrum of seed BHs.
Speaker 2: Mariska Kriek (Princeton Univ.)
Title: "AGNs and suppressed star formation in massive galaxies at z~2.5"
Abstract: The past few years have seen a tremendous increase in our knowledge of the galaxy population at 2<z<3. Recently it was found that red galaxies make up more than 2/3 of the most massive galaxies in this redshift range. As most of these galaxies are beyond the limits of optical spectroscopy they are underrepresented in available samples of high-redshift galaxies. To obtain a full spectroscopic census of the universe at z~2.5 we have conducted a near-infrared spectroscopic survey of 36 massive galaxies with GNIRS on Gemini-South and SINFONI on the VLT. A surprising result of our survey is the identification of massive galaxies at z~2.5 with strongly suppressed star formation: a significant fraction of the galaxies in our sample has no detected Halpha emission, is characterized by strong Balmer breaks, and is best fit by stellar population models with low star formation rates.
These galaxies already form a red sequence at z~2.5. Furthermore, we identified several AGNs in our massive galaxy sample by optical emission line ratios, mainly residing in galaxies with strongly suppressed star formation.
In this talk I will show our latest results, and discuss the implications for the formation histories of massive galaxies.