Jan 22

"Towards Advanced Study of Active Galactic Nuclei with Visible Light Adaptive Optics"
Mark Ammons, University of California at Santa Cruz

AGN feedback may contribute to quenching of star formation and evolution of galaxies onto the red sequence (e.g., Di Matteo et al. 2005, Hopkins et al. 2006). I probe for the effects of feedback on the stellar populations of ~10 X-ray selected AGN hosts at z ~ 1 in the GOODS-South field. Combining high spatial resolution optical imaging from HST ACS, and high spatial resolution near infrared data from Keck Laser Guide Star Adaptive Optics, I test for the presence of young stars on sub-kiloparsec scales, independent of dust extinction. I detect mean gradients in rest-frame NUV-R to ~400 pc, suggesting nonuniform stellar age mixtures. I observe little (< 0.05 mags) difference between the NUV-R gradients of the obscured sources and the unobscured sources, suggesting that the unobscured sources are not increasingly quenched of star formation. SED fitting of optical to IR colors at all radii reveals a correlation between the mass fraction of young (< 100 Myr) stars and AGN strength (as measured with [OIII] line luminosity), suggesting common conditions for star formation and black hole fueling. On larger spatial scales I incorporate deep VLT ISSAC JHK imaging and confirm these results on a larger sample of ~60 AGN. In contrast to local AGN, evidence from mid-IR colors suggests that the obscuration in Type II AGN at high redshift is due to kpc-scale dusty features rather than a small-scale dust torus. Our observations support the notions that (1) the obscuration in Type II AGN at z~1 may be due to kpc-scale dusty features, (2) cold gas is distributed in these sources, and (3) unobscured AGN do not appear to be increasingly quenched of star formation relative to obscured sources, although they lack cold dust.

Mar 12

Bulges, pseudo bulges, bars, velocity dispersions, star formation, and black hole masses - coevolution from the time of formation of the first galaxies to the present day, and other equally uninteresting topics.
Martin Gaskell, University of Texas at Austin

One of the most central problems in astrophysics is the intimate relationship between star formation in galaxies over cosmic time and the growth of supermassive black holes. I present a number of new results that potentially cast light on the puzzling relationships between supermassive black holes and the bulges of their host galaxies. Black hole masses derived from AGNs turn out to have surprisingly little scatter. An improved stellar velocity dispersion calibration implies that stellar dynamical mass estimates have been systematically too low, as has been independently suggested by Gebhardt & Thomas (2009), and that the M-sigma relationship is curved at high masses. This explains the lack of very high velocity dispersion galaxies found by Salviander et al. (2008). The improved stellar velocity dispersion calibration also reconciles the different evolution of the M-sigma relationship found by Shields et al. (2003) and Shields et al. (2006). The resulting apparent evolution is similar to what is expected from Malmquist bias. Use of the new high accuracy Kormendy et al. (2009) light profiles of bulge-dominate Virgo cluster galaxies to correct AGN host galaxy luminosity estimates for redshift- and luminosity-dependent aperture effects gives an improved M-L_host relationship. This shows that, as expected, black holes with higher Eddington accretion rates have less luminous host galaxies. The hosts of these high accretors show the strongest signs of secular evolution. Finally, I examine the proposal that the black holes which are currently growing most vigorously have systematically lower masses than are predicted by the M-sigma relationship.

Mar 26

Dead quasars, backlit galaxies, and other gems from the Galaxy Zoo
William C. Keel, University of Alabama

The Galaxy Zoo project has been a remarkable example of citizen science, engaging over 180,000 participants worldwide in detailed assessment of nearly a million galaxy images from the Sloan survey. I highlight some personal favorites from the harvest so far. Dutch schoolteacher Hanny van Arkel found an immense nebula ("Hanny's Voorwerp") which seems to be the ionization echo of a recently- defunct quasar in the local Universe, possibly opening a new time window to the history of AGN. Meanwhile, the sample of overlapping- galaxy pairs available to study dust properties has jumped from ~20 to >1500 as participants have culled them from the survey images. This has reopened their use to probe galaxy dust, now allowing distinctions in morphology and surface brightness, and adding GALEX data to probe ultraviolet extinction in galaxy disks. Galaxy classifications have driven home the point that the color bimodality in galaxies is not identically the same as the morphological one; blue-elliptical and red-spiral populations can be identified. Finally, I mention further developments and prospects for Zoo2,3,4...

Apr 02

A New Technique for Mining the SDSS QSO Archive and a Binary Black Hole Candidate
Todd Boroson, National Optical Astronomy Observatory (NOAO)

In order to use large datasets most effectively, astronomers must develop new tools that allow the compression and visualization of information. One such tool is the Karhunen-Loeve Transform, which has already been used to study the spectra of QSOs. This talk describes the application of the KL Transform to a set of 17,500 low-redshift QSO spectra as a tool for (a) improving the S/N of the spectra, (b) producing a manageable set of information that accurately and completely describes the data, and (c) identifying outliers that may have interesting or extreme properties. One of the outliers identified in this study is SDSS J1536+0441, an object with a complex line profile that may be indicative of a supermassive black hole binary system with a separation of 0.1 parsec.