The distant red galaxy neighbour population of 1 < z < 2 QSOs and optically obscured sources

Abstract

We study the Distant Red Galaxy (DRG, J-K_s > 2.3) neighbour population of Quasi Stellar Objects (QSOs) selected from the Sloan Digital Sky Survey (SDSS) in the redshift range 1 < z < 2. We perform a similar analysis for optically obscured AGNs (i.e. with a limiting magnitude I > 24) detected in the mid-infrared (24 $\mu$m) with the Spitzer Space Telescope and a mean redshift $z\sim 2.2$ in the Flamingos Extragalactic Survey (FLAMEX). Both QSOs and obscured AGN target samples cover 4.7 deg${}^2$ in the same region of the sky. We find a significant difference in the environment of these two target samples. Neighbouring galaxies close to QSOs tend to be bluer than galaxies in optically obscured source environments. We also present results on the cross-correlation function of DRGs around QSOs and optically faint mid-infrared sources. The corresponding correlation length obtained for the QSO sample targets is $r_0$=$5.4\pm 1.6$ Mpc h${}^{-1}$ and a slope of $\gamma$=$1.94\pm 0.10$ . For the optically obscured galaxy sample we find $r_0$=$8.9\pm 1.4$ Mpc h${}^{-1}$ and a slope of $\gamma$=$2.27\pm 0.20$. These results indicate that optically faint obscured sources are located in denser environment of evolved red galaxies compare to QSOs.

Accepted for publication in MNRAS, 9 pages including 5 PostScript figures and 3 tables

References in corpus (8)

• An Observational Determination of the Bolometric Quasar Luminosity Function
• The GOODS-MUSIC sample: a multicolour catalog of near-IR selected galaxies in the GOODS-South field
• The Small-Scale Environment of Quasars
• The Discovery of Three New z>5 Quasars in the AGN and Galaxy Evolution Survey
• Proto-Clusters with Evolved Populations around Radio Galaxies at z~2.5
• Properties of galaxies in SDSS Quasar environments at z < 0.2
• The Clustering Evolution of Distant Red Galaxies in the GOODS-MUSIC Sample
• Number counts and clustering properties of bright Distant Red Galaxies in the UKIDSS Ultra Deep Survey Early Data Release