We describe the properties of the Lyα forest in the column density range NH I ≥ 2× 10 12 cm based on 1056 lines in the wavelength range 4300− 5100 Å measured in extremely high S/N, R = 36, 000 spectra of four quasars. The column density distribution is well described by a −1.5 power law to 2×10 cm, below which limit confusion becomes too severe to measure a spectrum of individual clouds. The di...

Using the most recent (1998) version of the VLA FIRST survey radio catalog, we have searched for radio emission from 1704 quasars taken from the most recent (1993) version of the Hewitt and Burbidge quasar catalog. These quasars lie in the ∼5000 square degrees of sky already covered by the VLA FIRST survey. Our work has resulted in positive detection of radio emission from 389 quasars of which ...

We report on our XMM observations of the high redshift quasars BR 2237–0607 (z=4.558) and BR 0351–1034 (z=4.351), together with 14 other z> 4 objects found in the XMM public archive. Contrary to former reports, we do not find high redshift radio-loud quasars to be more absorbed than their radio-quiet counterparts. We find that the optical to X-ray spectral index αox is correlated with the lumin...

We present results from a mini-survey of relatively high redshift (1.7 < z < 4) gravitationally lensed radio-quiet quasars observed with the Chandra X-ray Observatory and with XMM-Newton. The lensing magnification effect allows us to search for changes in quasar spectroscopic and flux variability properties with redshift over three orders of magnitude in intrinsic X-ray luminosity. It extends t...

We present results of a study of 12 dust-reddened quasars with 0.4 < z < 2.65 and reddenings in the range 0.15 < E(B − V ) < 1.7. We obtained ACIS-S X-ray spectra of these quasars, estimated the column densities towards them, and hence obtained the gas:dust ratios in the material obscuring the quasar. We detect all but one of the red quasars in the X-rays. Even though there is no obvious correl...

Quasars represent a brief phase in the life-cycle of most massive galaxies, but the evolutionary connection between central black holes and their host galaxies remains unclear. While quasars are active and shining brighter than the Compton-limit luminosity, their radiation heats the surrounding medium to the Compton temperature, forming Compton spheres extending to the Strömgren radius of Fe26+...

We have searched for X-ray jets in the recent Chandra observations of three Sloan Digital Sky Survey (SDSS) quasars at redshift z ≈ 6. All 3 quasars were detected in X-rays in these relatively short observations. SDSS1030+0524 is not consistent with a point source, and may be a gravitationally lensed system. We find a possible jet-like feature 23 from the quasar SDSS 1306+0356. We can explain t...

We present an investigation of the environment (≈ 600 kpc radius) of a pair of luminous z = 4.25 quasars, SDSS J1439−0034 A,B, separated by 33. An analysis of high-quality Subaru spectra of the quasars suggests that this configuration is indeed a physical pair and not a gravitational lens; the redshifts are slightly different (although marginally consistent with being the same), and the two spe...