PI: Jill Bechtold, University of Arizona, firstname.lastname@example.org
Address: Astronomy Department, 933 N. Cherry Ave., Tucson, AZ 85721, USA
CoI: Kim McLeod, Wellesley College
CoI: Francesca d'Arcangelo, Wellesley College
Title: High Redshift Quasar Host Galaxies
Abstract: We propose to use NIRI to obtain deep K-band images of z~4 quasars, to investigate the cosmological evolution of quasar host galaxies. We recently showed that the spectra of the most luminous z>4 quasars, and their spectral energy distributions from X-rays to IR, imply very large central black hole masses - 10^10 - 10^11 M_\odot. This observational result challenges theories of quasar evolution, in which the black hole mass and host galaxy mass are expected to be progressively smaller at higher redshift because mergers take place as galaxy and large scale structure formation proceed. Pushing to high redshift with a large sample will provide the necessary leverage to enable definitive tests of the models. We aim to be sensitive to host galaxies of at least L^*. If the high redshift quasars follow the same correlation between black hole mass and stellar spheroid mass seen locally, then their hosts should be much more luminous than L^*, whereas if the merger theories are correct, then the hosts should be much less than L^*. K-band imaging is required because we want to sample rest frame wavelengths that are not dominated by the most recent starburst in the host. NIRI's large field of view with f/6 makes it superior to the IR imagers at Keck or the MMT for this project, because field stars will be contained in the images for characterization of the PSF. We cannot use AO because these rare objects lack suitable guide stars, even on 8m-class telescopes. NICMOS on HST offers no advantage, since the PSF is comparable (0.22 \arcsec at K) to the best seeing with a large telescope on the ground, and because the 8m Gemini aperture enables deeper observations.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360