Wang et al. (2006) estimated an average radiative efficiency of 30%–35% for quasars at moderate redshift. We find that their method is not independent of quasar lifetimes and thus that quasars do not necessarily have such high efficiencies. Nonetheless, it is possible to derive interrelated constraints on quasar lifetimes, Eddington ratios, and radiative efficiencies of supermassive black holes...

We compare the metallicities in high-redshift quasars to the star formation rates (SFR) in their host galaxies using measurements of broad emission lines and far-infrared (FIR) luminosities. The FIR emission indicates the level of ongoing massive starbursts in the galaxy, whereas the abundance of metals in the gas surrounding the quasar indicates the amount of star formation which occurred befo...

The discovery that the formation and evolution of supermassive black holes and their host spheroids are intimately related has given new impetus to the study of quasar host galaxies. As a result, many current studies of quasar hosts are focused on exploring the redshift evolution of the black-hole:spheroid relation, and the evolution of the massive galaxy population as a whole. This brief revie...

We analyse the environment of low redshift, z < 0.2, SDSS quasars using the spectral and photometric information of galaxies from the Sloan Digital Sky Survey Third Data Release (SDSS-DR3). We compare quasar neighbourhoods with field and high density environments through an analysis on samples of typical galaxies and groups. We compute the surrounding surface number density of galaxies finding ...

We consider implications of our new model of quasar lifetimes and light curves for the quasar luminosity function (LF) at different frequencies and redshifts. In our picture, quasars evolve rapidly and the lifetime depends on both their instantaneous and peak luminosities. The bright end of the LF traces the peak intrinsic quasar activity, but the faint end consists of quasars which are either ...

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable th...

Context. While there is growing consensus on the existence of numerous dust-enshrouded red quasars, their discovery and detailed exploration is still an observational challenge. In the course of the near-mid-infrared AGN search combining the 6.7 μm ISOCAM Parallel Survey and 2MASS we have discovered 24 type-1 quasars about a third of which are too red to be discriminated by optical/UV search te...

Using a homogenous sample of 38,208 quasars with a sky coverage of ∼ 4000deg2 drawn from the SDSS Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole mass, quasar color, and radio loudness. At z < 2.5, quasar clustering depends weakly on luminosity and virial black hole mass, with typical uncertainty levels ∼ 10% for the measured corre...

Although the population of luminous quasars rises and falls over a period of ∼ 109 years, the typical lifetime of individual quasars is uncertain by several orders of magnitude. We show that quasar clustering measurements can substantially narrow the range of possible lifetimes with the assumption that luminous quasars reside in the most massive host halos. If quasars are long-lived, then they ...