Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z 6.4, a limit set by the use of the z-band and CCD detectors. Only one z 6.4 quasar has been discovered, namely the z = 7.08 quasar ULAS J1120+0641, using near-inf...

We present deep, multi-VLA-configuration radio images for a set of 18 quasars, having redshifts between 0.36 and 2.5, from the 7C quasar survey. Approximately one quarter of these quasars have FR I-type twin-jet structures and the remainder are a broad range of wide angle tail, fat double, classical double, core-jet and hybrid sources. These images demonstrate that FR I quasars are prevalent in...

We present JHKL photometry of a complete sample of steep-spectrum radio-loud quasars from the revised 3CR catalogue in the redshift range 0.65 ≤ z < 1.20. After correcting for contributions from emission lines and the host galaxies, we investigate their spectral energy distributions (SEDs) around 1μm. About 75% of the quasars are tightly grouped in the plane of optical spectral index, αopt, ver...

We use host galaxy imaging studies of the PG Quasar survey to compare the farinfrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogenous data set, have a 60μm luminosity distribution that is different from that of those with undisturbed hosts w...

We present the discovery of six new quasars at z ∼ 6 selected from the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator. The six quasars are about two magnitudes fainter than the luminous z ∼ 6 quasars found in the SDSS main survey and one magnitude fainter than the quasars reported in Paper I (Jiang et a...

We use 250 radio loud quasars with UBV photometry available and z < 1.65, to study whether there is a gap in the distribution of absolute magnitudes, from MV ≈ −25.8 (for Ho = 100 kms−1 Mpc−1, qo = 0.5) to −25.3, as was suggested by Teerikorpi (1981b; Paper I). In Paper I it was also proposed that there is a class of the most luminous radio quasars, differing in some properties from fainter qua...

We present results from the first phase of the Seoul National University Bright Quasar Survey in Optical (SNUQSO) as well as its basic observational setup. Previous and current large area surveys have been successful in identifying many quasars, but they could have missed bright quasars due to their survey design. In order to help complete the census of bright quasars, we have performed spectro...

Black-hole masses of the highest redshift quasars (4 < ∼ z < ∼ 6) are estimated using a previously presented scaling relationship, derived from reverberation mapping of nearby quasars, and compared to quasars at lower redshift. It is shown that the central black holes in luminous z > ∼ 4 quasars are very massive ( ∼ 10M⊙). It is argued that the mass estimates of the high-z quasars are not subje...

We present the results of multi-wavelength observations of cores and hotspots at L, C, X and U bands with the Very Large Array, of a matched sample of radio galaxies and quasars selected from the Molonglo Reference Catalogue. We use these observations to determine the spectra of cores and hotspots, and test the unified scheme for radio galaxies and quasars. Radio cores have been detected at all...

We present Chandra observations of 18 spectroscopically selected quasars, already known to be X-ray weak from previous ROSAT observations. All the sources but one are detected by Chandra, and spectral analysis suggests that most of them are intrinsically underluminous in the X-rays (by a factor from 3 to > 100). These objects could represent a large population of quasars with a Spectral Energy ...