Quasars at intermediate redshift are not special; but they are often satellites

Shadab Alam,John A Peacock,Ashley J Ross,Johan Comparat,Nicholas P Ross,Adam D Myers,Sarah Eftekharzadeh

doi:10.1093/mnras/stab898

Abstract

ABSTRACT Understanding the links between the activity of supermassive black holes (SMBHs) at the centres of galaxies and their host dark matter haloes is a key question in modern astrophysics. The final data release of the SDSS-IV eBOSS provides the largest contemporary spectroscopic sample of galaxies and quasi-stellar objects (QSOs). Using this sample and covering the redshift interval z = 0.7–1.1, we have measured the clustering properties of the eBOSS QSOs, emission-line galaxies (ELGs), and luminous red galaxies (LRGs). We have also measured the fraction of QSOs as a function of the overdensity defined by the galaxy population. Using these measurements, we investigate how QSOs populate and sample the galaxy population, and how the host dark-matter haloes of QSOs sample the underlying halo distribution. We find that the probability of a galaxy hosting a QSO is independent of the host dark matter halo mass of the galaxy. We also find that about 60 per cent of eBOSS QSOs are hosted by LRGs and about 20–40 per cent of QSOs are hosted by satellite galaxies. We find a slight preference for QSOs to populate satellite galaxies over central galaxies. This is connected to the host halo mass distribution of different types of galaxies. Based on our analysis, QSOs should be hosted by a very broad distribution of haloes, and their occurrence should be modulated only by the efficiency of galaxy formation processes.

Highlights

Two outstanding questions in extragalactic astrophysics are the manner in which galaxies sample the dark matter (DM) halo mass function, and how active galactic nuclei (AGN) sample the galaxy population
Our goal is to investigate a series of halo occupation distribution (HOD) models that described how Quasi-Stellar Objects (QSOs) populate the distribution of dark matter haloes
The probability that a galaxy has quasar activity is independent of dark matter halo mass

Summary

Introduction

Two outstanding questions in extragalactic astrophysics are the manner in which galaxies sample the dark matter (DM) halo mass function, and how active galactic nuclei (AGN) sample the galaxy population These questions are central because it is believed that the energy and kinematics associated with AGN are crucial in understanding how galaxies form and regulate their star formation Fabian 2012; Kormendy & Ho 2013; Madau & Dickinson 2014; King & Pounds 2015; Somerville & Davé 2015; Xue 2017; Padovani et al 2017) They are rare, QSOs (generally defined as luminous AGN with bolometric luminosities Lbol above ∼1038 W) have become key tracers of the large-scale structure (LSS) of the Universe (e.g. Coil et al 2004; Outram et al 2004; Croom et al 2005; Myers et al 2007; Shen et al 2007; da Ângela et al 2008; Ross et al 2009; He et al 2018; Neveux et al 2020; Hou et al 2021; Oogi et al 2020). The bias parameter, b, is typically determined on linear scales ∼ 5 − 30 h−1Mpc, and this measurement and comparison has been carried out for a range of QSO redshifts, luminosities and colours

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