Abstract
Despite substantial effort, the precise physical processes that lead to the growth of super-massive black holes in the centers of galaxies are still not well understood. These phases of black hole growth are thought to be of key importance in understanding galaxy evolution. Forthcoming missions such as eROSITA, HETDEX, eBOSS, BigBOSS, LSST, and Pan-STARRS will compile by far the largest ever Active Galactic Nuclei (AGNs) catalogs which will allow us to measure the spatial distribution of AGNs in the universe with unprecedented accuracy. For the first time, AGN clustering measurements will reach a level of precision that will not only allow for an alternative approach to answering open questions in AGN and galaxy co-evolution but will open a new frontier, allowing us to precisely determine cosmological parameters. This paper reviews large-scale clustering measurements of broad line AGNs. We summarize how clustering is measured and which constraints can be derived from AGN clustering measurements, we discuss recent developments, and we briefly describe future projects that will deliver extremely large AGN samples which will enable AGN clustering measurements of unprecedented accuracy. In order to maximize the scientific return on the research fields of AGN and galaxy evolution and cosmology, we advise that the community develops a full understanding of the systematic uncertainties which will, in contrast to today’s measurement, be the dominant source of uncertainty.
Highlights
Large area surveys such as the Two Degree Field Galaxy Redshift Survey (2dFGRS; Colless et al 2001) and the Sloan Digital Sky Survey (SDSS; Abazajian et al 2009) have measured positions and redshifts of millions of galaxies
Forthcoming missions such as eROSITA, HETDEX, eBOSS, BigBOSS, LSST, and PanSTARRS will compile by far the largest ever Active Galactic Nuclei (AGNs) catalogs which will allow us to measure the spatial distribution of Active Galactic Nucleus (AGN) in the universe with unprecedented accuracy
We summarize how clustering is measured and which constraints can be derived from AGN clustering measurements, we discuss recent developments, and we briefly describe future projects that will deliver extremely large AGN samples which will enable AGN clustering measurements of unprecedented accuracy
Summary
Large area surveys such as the Two Degree Field Galaxy Redshift Survey (2dFGRS; Colless et al 2001) and the Sloan Digital Sky Survey (SDSS; Abazajian et al 2009) have measured positions and redshifts of millions of galaxies. Since AGNs are generally much brighter than (inactive) galaxies, one major advantage of AGN large-scale (i.e., larger than the size of a galaxy) clustering measurements over galaxy clustering measurements is that they allow the study of the matter distribution in the universe out to higher redshifts At these redshifts, it becomes challenging and observationally expensive to detect galaxies in sufficient numbers. As only a very small fraction of galaxies contain an AGN (∼1%), the remaining and dominating challenge in deriving physical constraints based on AGN clustering measurements is the relative small sample size compared to galaxy clustering measurements This situation will change entirely in the decade when several different surveys come online that are expected to identify millions of AGN over ∼80% of cosmic time. Different cosmological models lead to different properties of the DMH population
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