Blue outliers among intermediate redshift quasars

Adaptive optics imaging of low and intermediate redshift quasars ⋆

We present the results of adaptive-optics imaging in the H and K bands of 12 low and intermediate redshift (z < 0.6) quasars using the PUEO system mounted on the Canada-France-Hawaii telescope. Five quasars are radio-quiet and seven are radio-loud. The images, obtained under poor seeing conditions, and with the QSOs (mV > 15.0) themselves as reference for the correction, have typical spatial re...

High - redshift obscured quasars

Using mid-infrared and radio criteria, we select a sample of candidate z ∼ 2 obscured quasars. Optical spectroscopy confirms about half of these as type-2 quasars, and modelling the population suggests 50-80% of the quasars are obscured. We find some flat radio spectrum type-2 quasars, and tentative evidence for obscuration unrelated to the torus. Using a similar sample, we also find evidence f...

Intrinsic redshift in quasars

High-Redshift, Radio-Loud Quasars

I discuss two programs to study radio-loud quasars at high (z ∼ > 4) redshift. Quasars are the most luminous, non-transient objects known and are observed to the earliest cosmic epochs. At lower redshifts, radio-loud quasars are associated with host galaxies having de Vaucoleurs profiles. By association, identifying and studying a sample of high-redshift, radio-loud quasars provides important c...

Line and continuum variability of two intermediate - redshift , high - luminosity quasars

Context. It has been shown that the luminosity of active galactic nuclei and the size of their broad line region obey a simple relation of the type RBLR = aL, from faint Seyfert nuclei to bright quasars, allowing single-epoch determination of the central black hole mass MBH = bL∆Hβ from their luminosity L and width of Hβ emission line. Adopting this mass determination for cosmological studies r...