Starting from the quasar sample of the Sloan Digital Sky Survey (SDSS) for which the Civ line is observed, we use an analysis scheme to derive the z-dependence of the maximum mass of active black holes, which overcomes the problems related to the Malmquist bias. The same procedure is applied to the low redshift sample of SDSS quasars for which Hβ measurements are available. Combining with the r...

We present observations of RD J030117+002025, a quasar at z=5.50 discovered from deep, multicolor, ground-based observations covering 74 arcmin2. This is the most distant quasar or active galaxy currently known. The object was targeted as an R-band dropout, with RAB>26.3 (3 sigma limit in a 3&arcsec; diameter region), IAB=23.8, and zAB=23.4. The Keck/Low-Resolution Imaging Spectrometer spectrum...

If the unexpectedly high frequency of quasar pairs with very different component redshifts is due to the lensing of a population of background quasars by the foreground quasar, typical lens masses must be ∼ 10M⊙ and the sum of all such quasar lenses would have to contain ∼ 0.005 times the closure density of the Universe. It then seems plausible that a very high fraction of all ∼ 10M⊙ gravitatio...

We report a serendipitous discovery of broad absorption lines that were newly formed in the spectrum of the high-redshift, luminous radio-loud quasar TEX 1726+344, in a time interval of only 12 years. This is the first quasar showing a transition from narrow absorption lines to broad absorption lines. It also becomes one of the few radio-loud broad absorption line quasars. The gas cloud respons...

Observations of the cold, dense gas at high redshifts directly address fundamental questions regarding the early evolution of galaxies and quasars. The Owens Valley Millimeter Array provides excellent sensitivity and resolutions better than 1 00. The spatial distribution of red-shifted CO emission is found to be resolved in most detected objects. For example, 1 kpc size scale for the CO emittin...

We present Hubble Space Telescope ACS images of 13 dust-reddened type 1 quasars selected from the FIRST/ 2MASS Red Quasar Survey. These quasars have high intrinsic luminosities after correction for dust obscuration ( 23:5 MB 26:2 from K-magnitude). The images show strong evidence of recent or ongoing interaction in 11 of the 13 cases, even before the quasar nucleus is subtracted. None of the ho...

The theoretically expected amplitude of the associations of background quasars with foreground galaxies as a result of gravitational lensing has been updated in this paper. Since the galactic matter alone yields an amplitude of quasar overdensity smaller than that observed, a special attention has been paid to the examination or re-examination of the uncertainties in the estimate of the quasar ...

The STIS Hubble Deep Field South around the quasar J2233−606 was observed in the course of the VLT-UT1 Science Verification programme with the Test Camera in two broad-band filters, B and R, and in a narrow-band filter roughly centered at the quasar emission redshift, zem = 2.238. The most striking result is the discovery of a giant Lyα nebulosity around this radio-weak quasar, with an overall ...

We present the initial results from our search for high redshift, z & 6, quasars using near infrared data from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Our analysis of 106 deg of sky from Data Release 1 (DR1) has resulted in the discovery of ULAS J020332.38+001229.2, a luminous (JAB = 20.0, JVega = 19.1, M1450 = −26.2) quasar at z = 5.86. Following candidate selectio...