First Measurement of the Clustering Evolution of Photometrically Classified Quasars

Abstract

We present new measurements of the quasar angular autocorrelation function from a sample of $80,000 photometrically classified quasars taken from the First Data Release of the Sloan Digital Sky Survey. We find a best-fit model of !() ¼ (0:066 þ0:026 À0:024 ) À ( 0:98AE0:15 ) for the angular correlation function, consistent with estimates of the slope from spectroscopic quasar surveys. We show that only models with little or no evolution in the clustering of quasars in comoving coordinates since a median redshift of z $ 1:4 can recover a scale length consistent with local galaxies and active galactic nuclei (AGNs). A model with little evolution of quasar clustering in comoving coordinates is best explained in the current cosmological paradigm by rapid evolution in quasar bias. We show that quasar biasing must have changed from b Q $ 3 at a (photometric) redshift ofz phot ¼ 2:2 to b Q $ 1:2 1:3 byz phot ¼ 0:75. Such a rapid increase with redshift in biasing implies that quasars at z $ 2 cannot be the progenitors of modern L Ã objects; rather they must now reside in dense environments, such as clusters. Similarly, the duration of the UVX (ultraviolet-excess) quasar phase must be short enough to explain why local UVX quasars reside in essentially unbiased structures. Our estimates of b Q are in good agreement with recent spectroscopic results , which demonstrate that the implied evolution in b Q is consistent with quasars inhabiting halos of similar mass at every redshift. Treating quasar clustering as a bivariate function of both redshift and luminosity, we find no evidence for luminosity dependence in quasar clustering, and that redshift evolution thus affects quasar clustering more than changes in quasars' luminosity. Our results are robust against a range of systematic uncertainties. We provide a new method for quantifying stellar contamination in photometrically classified quasar catalogs via the correlation function. Subject headingg s: cosmology: observations -large-scale structure of universe -quasars: general -surveys

Dusty star-forming galaxies at high redshift

“…Figure 39: Auto-correlation length r 0 of DSFGs compared to a variety of galaxy populations over the redshift interval 0 < z < 3. These include optically-selected SDSS QSOs at 0 < z < 3 (Myers et al, 2006;Ross et al, 2009) Lyman-break galaxies (Adelberger et al, 2005), MIPS 24 µm-selected star-forming galaxies at 0 < z < 1.4 , AGES and DEEP2 red and blue galaxies at 0.25 < z < 1 from the AGES (Hickox et al, 2009;Coil et al, 2008) SDSS-selected luminous red galaxies (LRGs) at 0 < z < 0.7 (Wake et al, 2008), and optically-selected galaxy clusters at 0.1 < z < 0.3 (Estrada et al, 2009). The figure also shows the r 0 for low-redshift galaxies with r-band luminosities in the range 1.5 to 3.5 L , derived from the luminosity dependence of clustering (Zehavi et al, 2011).…”

Clustering on very small scales from a large sample of confirmed quasar pairs: does quasar clustering track from Mpc to kpc scales?

“…An appropriate random catalogue will mimic the angular and redshift distribution of the data, in the absence of any clustering. Since our KDE-complete sample of binary quasars is drawn from the KDE catalogue described in §2, the random catalogue needs to have the same overall angular and redshift coverage as the KDE catalogue (see, e.g., Myers et al 2006Myers et al , 2007a. The entire volume of the KDE catalogue comprises ∼ 41.93 (h −1 Gpc ) 3 .…”

Dark matter annihilation or unresolved astrophysical sources? Anisotropy probe of the origin of the cosmic gamma-ray background

“…(This measurement is, however, limited to the bias of resolved blazars, which can be different from the bias of unresolved blazars which contribute to the CGB anisotropy.) At the moment, one may estimate b B L; z from several approaches including the angular and spatial correlation analysis of optical quasars [51,52] …”