Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a binary quasar or a doubly-imaged lensed quasar. Direct search of a putative lensing galaxy is unsuccessful down to R=27, J=24, Ks=22.5 and H=22.5. Moreover, no galaxy overdensity close to the quasar pair is found. A weak shear analysis of the FOR...

We present observations of an optically-faint quasar, RD J114816.2+525339 (hereafter RD J1148+5253), discovered from deep multi-color observations of the field around the z = 6.42 quasar SDSS J1148+5251. The two quasars have a projected separation of 109 and both are outliers in r−z versus z−J color-color space. Keck spectroscopy reveals RD J1148+5253 to be a broad-absorption line quasar at z =...

We propose a new interpretation of the quasar luminosity function (LF), derived from physically motivated models of quasar lifetimes and light curves. In our picture, quasars evolve rapidly and their lifetime depends on both their instantaneous and peak luminosities. We study this model using simulations of galaxy mergers that successfully reproduce a wide range of observed quasar phenomena. Wi...

Two recent studies based on composite reddened quasar spectra have indicated the presence of ‘gray’ dust in quasar environments. This gray dust has a relatively flat extinction law in the UV, consistent with the theoretical expectation of a lack of small dust grains close to a quasar. In contrast, individual reddened quasars in the Sloan Digital Sky Survey tend to have steep extinction laws in ...

We report the discovery of a new two-image gravitational lens candidate. The system RXJ0921+4529 contains two zs = 1.66 quasars separated by 6. 93 with an H band magnitude difference of ∆m = 1.39. The HST NIC2 H band images reveal an H=18.2 spiral galaxy between the quasar images, which is probably a member of a zl = 0.32 X-ray cluster centered on the field. We detect an extended source near th...

We present a quasar candidate identification technique based on multicolor photometry. The traditional multi-dimensional method (2 × N dimensions, where N is the number of filters) is reduced to a one-dimensional technique, which consists in a standard fitting procedure, where the observed spectral energy distributions are compared to quasar simulated spectra and stellar templates. This new mul...

After a short review of the quasar problem and what we can hope to learn from their emission line spectra, I discuss the current body of knowledge concerning quasar emission lines and their relationships to the local and ionizing continua. I propose a hypothesis that the Baldwin effect is due to a characteristic relationship between the continuum spectral energy distribution, the gas metallicit...

Based on numerical simulations of galaxy mergers that incorporate black hole growth, we predict the faint end slope of the quasar luminosity function (QLF) and its evolution with redshift. Our simulations have yielded a new model for quasar lifetimes and light curves where the lifetime depends on both the instantaneous and peak luminosities of the quasar. This description motivates a new interp...

Two recent studies based on composite reddened quasar spectra have indicated the presence of ‘grey’ dust in quasar environments. This grey dust has a relatively flat extinction law in the UV, consistent with the theoretical expectation of a lack of small dust grains close to a quasar. In contrast, individual reddened quasars in the SDSS tend to have steep extinction laws in the UV, similar to t...