We report the discovery of a quasar at z = 3.050 ± 0.003, closely coincident in redshift with the isolated low-opacity feature seen near z 3.056 in the otherwise black portion of the He  Gunn-Peterson absorption trough seen toward the z = 3.286 background quasar Q0302−003, located 6. 5 away on the sky. We explore plausible models for the He  ionization zone created by this neighboring quas...

Using a model for the self-regulated growth of supermassive black holes in mergers involving gas-rich galaxies, we study the relationship between quasars and the population of merging galaxies and, as a consequence, predict the merger-induced star formation rate density of the Universe. These mergers drive nuclear inflows of gas, fueling starbursts and “buried” quasar activity until feedback en...

Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines – the ‘quasar fraction’ – as a fu...

We study quasar clustering on small scales, modeling clustering amplitudes using halo-driven dark matter descriptions. From 91 pairs on scales < 35 h kpc, we detect only a slight excess in quasar clustering over our best-fit large-scale model. Integrated across all redshifts, the implied quasar bias is bQ = 4.21± 0.98 (bQ = 3.93± 0.71) at ∼18 h −1 kpc (∼28 h kpc). Our best-fit (real-space) powe...

We present a simple framework for the growth and evolution of supermassive black holes (SMBHs) in the hierarchical structure formation paradigm, adopting the general idea that quasar activity is triggered in major mergers. In our model, black hole accretion is triggered during major mergers (mass ratio & 0.3) between host dark matter halos. The successive evolution of quasar luminosities follow...

We propose a model of quasar lifetimes in which observational quasar lifetimes and an intrinsic lifetime of rapid accretion are strongly distinguished by the physics of obscuration by surrounding gas and dust. Quasars are powered by gas funneled to galaxy centers, but for a large part of the accretion lifetime they are heavily obscured by the large gas densities powering accretion. During this ...

We obtained medium-resolution spectra of 336 quasar candidates in the COSMOS HST/Treasury field using the MMT 6.5-meter telescope and the Hectospec multi-object spectrograph. Candidates were drawn from the Sloan Digital Sky Survey (SDSS) DR1 catalog using quasar flags set by the SDSS multi-color quasar target selection algorithm. In this paper we present our discovery spectra from 1.39 square d...

The mass of massive black holes in quasar cores can be deduced using the typical velocities of Hβ-emitting clouds in the Broad Line Region (BLR) and the size of this region. However, this estimate depends on various assumptions and is susceptible to large systematic errors. The Hβ-deduced black hole mass in a sample of 14 bright quasars is found here to correlate with the quasar host galaxy lum...

The timescale of quasar variability is widely expected to show the effects of time dilation. In this paper we analyse the Fourier power spectra of a large sample of quasar light curves to look for such an effect. We find that the timescale of quasar variation does not increase with redshift as required by time dilation. Possible explanations of this result all conflict with widely held consensu...

Using a model for the self-regulated growth of supermassive black holes in mergers involving gas-rich galaxies, we study the relationship between quasars and the population of merging galaxies and thereby predict the merger-driven star formation rate density of the Universe. In our picture, mergers drive gas inflows, fueling nuclear starbursts and “buried” quasars until feedback disperses the g...