The Luminosity Dependence of Quasar Clustering

Adam Lidz,Thomas J Cox,Lars Hernquist,Philip F Hopkins,Brant Robertson

doi:10.1086/500444

Adam Lidz, Thomas J Cox + Show 3 more

Open Access

https://doi.org/10.1086/500444

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Abstract

We investigate the luminosity dependence of quasar clustering, inspired by numerical simulations of galaxy mergers that incorporate black hole growth. These simulations have motivated a new interpretation of the quasar luminosity function. In this picture, the bright end of the quasar luminosity function consists of quasars radiating nearly at their peak luminosities, while the faint end consists mainly of very similar sources, but at dimmer phases in their evolution. We combine this model with the statistics of dark matter halos that host quasar activity. We find that, since bright and faint quasars are mostly similar sources seen in different evolutionary stages, a broad range in quasar luminosities corresponds to only a narrow range in the masses of quasar host halos. On average, bright and faint quasars reside in similar host halos. Consequently, we argue that quasar clustering should depend only weakly on luminosity. This prediction is in qualitative agreement with recent measurements of the luminosity dependence of the quasar correlation function (Croom et al.) and the galaxy-quasar cross-correlation function (Adelberger & Steidel). Future precision clustering measurements from the Sloan Digital Sky Survey (SDSS) and the Two Degree Field Survey (2dF), spanning a large range in luminosity, should provide a strong test of our model.

Highlights

We investigate the luminosity dependence of quasar clustering, inspired by numerical simulations of galaxy mergers that incorporate black hole growth
The luminosity dependence of quasar clustering is poorly determined at each redshift we consider, and measurements at different redshifts do not currently provide a strong test of our contention that bright and faint quasars reside in similar mass host halos
We have connected the properties of quasars, as determined from numerical simulations of galaxy mergers (Springel et al 2005a, Di Matteo et al 2005, Robertson et al 2005), to the properties of the dark matter halos that host them

Summary

INTRODUCTION

Black hole growth and feedback have been incorporated into numerical simulations of galaxy mergers (Springel et al 2005a,b). As the black holes accrete, some of the radiated energy couples to the surrounding gas, and the growth eventually stalls when this feedback energy is sufficient to unbind the surrounding reservoir of gas These simulations elucidate the connection between galaxy evolution, the formation of supermassive black holes, and the self-regulated nature of quasar activity, and provide quantitative predictions which agree well with observations of, e.g., the MBH −σ relation (Di Matteo et al 2005, Robertson et al 2005), quasar lifetimes (Hopkins et al 2005a,b), and the quasar luminosity function in various wavebands (Hopkins et al 2005c,d,e). Adelberger & Steidel (2005) have recently measured the galaxy-quasar cross correlation function, finding no evidence for luminosity-dependent clustering Their interpretation of this observation is that faint quasars are longer-lived than bright quasars.

THE RELATION BETWEEN QUASAR LUMINOSITY AND HALO MASS

The Quasar Light Curve

WHICH DARK MATTER HALOS HOST ACTIVE QUASARS?

REDSHIFT EVOLUTION

CONCLUSION