AGN and QSOs in the eROSITA All-Sky Survey

II. The large-scale structure

¹ Max-Planck-Institut für Astrophysik (MPA), Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
e-mail: alex@mpa-garching.mpg.de
² Space Research Institute (IKI), Russian Academy of Sciences, Profsoyuznaya ul. 84/32, 117997 Moscow, Russia
³ Tartu Observatory, 61602 Tõravere, Estonia

Received: 2 May 2013
Accepted: 22 August 2013

Abstract

The four-year X-ray all-sky survey (eRASS) of the eROSITA telescope aboard the Spektrum-Roentgen-Gamma satellite will detect about 3 million active galactic nuclei (AGN) with a median redshift of z ≈ 1 and a typical luminosity of L_{0.5−2.0 keV} ~ 10⁴⁴ ergs^-1. We show that this unprecedented AGN sample, complemented with redshift information, will supply us with outstanding opportunities for large-scale structure research. For the first time, detailed redshift- and luminosity-resolved studies of the bias factor for X-ray selected AGN will become possible. The eRASS AGN sample will not only improve the redshift- and luminosity resolution of these studies, but will also expand their luminosity range beyond L_{0.5−2.0 keV} ~ 10⁴⁴ ergs^-1, thus enabling a direct comparison of the clustering properties of luminous X-ray AGN and optical quasars. These studies will dramatically improve our understanding of the AGN environment, triggering mechanisms, the growth of supermassive black holes and their co-evolution with dark matter halos. The eRASS AGN sample will become a powerful cosmological probe. It will enable detecting baryonic acoustic oscillations (BAOs) for the first time with X-ray selected AGN. With the data from the entire extragalactic sky, BAO will be detected at a ≳10σ confidence level in the full redshift range and with ~8σ confidence in the 0.8 < z < 2.0 range, which is currently not covered by any existing BAO surveys. To exploit the full potential of the eRASS AGN sample, photometric and spectroscopic surveys of large areas and a sufficient depth will be needed.