Host Galaxies of Luminous Type 2 Quasars at z ~ 0.5 - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado

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Abstract: We present deep Gemini GMOS optical spectroscopy of nine luminous quasars atredshifts z ~ 0.5, drawn from the SDSS type 2 quasar sample. Our targets wereselected to have high intrinsic luminosities M V < -26 mag as indicated bythe O III 5007 A emission-line luminosity L O III. Our sample has amedian black hole mass of ~ 10^8.8 M sun inferred assuming the localM BH-sigma * relation and a median Eddington ratio of ~ 0.7, using stellarvelocity dispersions sigma * measured from the G band. We estimate thecontamination of the stellar continuum from scattered quasar light based on thestrength of broad H-beta, and provide an empirical calibration of thecontamination as a function of L O III; the scattered light fraction is ~ 30%of L 5100 for objects with L O III = 10^9.5 L sun. Population synthesisindicates that young post-starburst populations < 0.1 Gyr are prevalent inluminous type 2 quasars, in addition to a relatively old population > 1 Gyrwhich dominates the stellar mass. Broad emission complexes around He II 4686 Awith luminosities up to 10^8.3 L sun are unambiguously detected in three out ofthe nine targets, indicative of Wolf-Rayet populations. Population synthesisshows that ~ 5-Myr post-starburst populations contribute substantially to theluminosities > 50% of L 5100 of all three objects with Wolf-Rayet detections.We find two objects with double cores and four with close companions. Ourresults may suggest that luminous type 2 quasars trace an early stage of galaxyinteraction, perhaps responsible for both the quasar and the starburstactivity.

Autor: Xin Liu, Nadia L. Zakamska, Jenny E. Greene, Michael A. Strauss, Julian H. Krolik, Timothy M. Heckman


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