Clustering Measurements of broad-line AGNs: Review and Future

TL;DR

This review discusses the current state and future prospects of clustering measurements of broad-line AGNs, emphasizing their importance for understanding galaxy evolution and cosmology with upcoming large surveys.

Contribution

It provides a comprehensive overview of AGN clustering measurement techniques, recent developments, and future projects, highlighting the need to understand systematic uncertainties.

Findings

Upcoming surveys will vastly increase AGN samples for clustering analysis.

AGN clustering measurements can constrain galaxy evolution and cosmological parameters.

Systematic uncertainties will become the dominant challenge in future measurements.

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/galaxy co-evolution but will open a new frontier, allowing us to precisely determine cosmological parameters. This paper reviews the 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/galaxy evolution and cosmology, we advise that the community develop a full understanding of the systematic uncertainties which will, in contrast to today's measurement, be the dominant source of uncertainty.