The Angular Diameter-Redshift Test for Large Redshift Quasars

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...

Color-redshift relations and photometric redshift estimations of quasars in large sky surveys

With a recently constructed composite quasar spectrum and the χ minimization technique, we demonstrated a general method to estimate the photometric redshifts of a large sample of quasars by deriving the theoretical colorredshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in...

The “ angular size – redshift ” relation for compact radio structures in quasars and radio galaxies ?

We discuss the “angular size – redshift” relation for compact radio sources distributed over a wide range of redshifts 0.011 ≤ z ≤ 4.72. Our study is based on a sample of 330 5 GHz VLBI contour maps taken from the literature. Unlike extended source samples, the “angular size – redshift” relation for compact radio sources appears consistent with the predictions of standard Friedmann world models...