Pointed ASCA observations as well as archival ROSAT data are used for a study of the X-ray emission of the three BAL Quasars LBQS 2212-1759, PG 1411+442, and PG 0043+039. All three objects are found to be X-ray quiet, possibly due to substantial intrinsic absorption with NH > 1023 cm−2 but might have intrinsically a more typical spectral energy distribution. This picture is supported by explici...

X-ray and optical observations of quadruply lensed quasars can provide a micro-arcsecond probe of the lensed quasar. In this paper we utilize X-ray observations of ten lensed quasars recorded with the Chandra X-ray Observatory as well as corresponding optical data obtained by either the Hubble Space Telescope or ground-based optical telescopes. These are analyzed in a systematic and uniform way...

We present a technique to explore the radio sky into the nanoJansky regime by employing image stacking using the FIRST survey. We begin with a discussion of the non-intuitive relationship between the mean and median values of a non-Gaussian distribution in which measurements of the members of the distribution are dominated by noise. Following a detailed examination of the systematic effects pre...

We present results on a multiwavelength campaign to identify the nature of dust-reddened Type 1 quasars. These quasars were selected by matching FIRST, 2MASS and very red optical counterparts with r − K > 5. We find a very high fraction of Low Ionization Broad Absorption Line Quasars (LoBALs) among AGN selected with this method, perhaps a sign of quasar feedback. From X-ray observations and Bal...

We have conducted an optical study of the environments of seven radio-loud quasars at redshifts 1 < z < 1.6. In this paper we describe deep B and R band images obtained for fields of ∼6×6 arcmin around these quasars with 3σ limiting magnitudes of B ∼ 26 and R ∼ 25.4. We found an statistically significant excess of faint (B > 22.5 and R > 22.0) galaxies on scales of r <170′′ and r <35′′ around t...

We construct the first X-ray selected sample of radio-loud quasars from the EMSS survey. The X–ray selection allows us to explore the properties of radio–loud quasars 10–100 weaker than classical samples in the radio band. There are no radio–loud quasars whose synchrotron peak reaches the UV–soft X–ray band at these (radio) flux levels (as occurs for BL Lac objects selected in the X–ray band), ...

We present near-infrared imaging obtained with ESO VLT+ISAAC of the host galaxies of a sample of low luminosity quasars in the redshift range 1 < z < 2, aimed at investigating the relationship between the nuclear and host galaxy luminosities at high redshift. This work complements our previous systematic study to trace the cosmological evolution of the host galaxies of high luminosity quasars (...

Much evidence has been presented in favor of and against the existence of two distinct populations of quasars, radio-loud and radio-quiet. The SDSS differs from earlier optically selected quasar surveys in the large number of quasars and the targeting of FIRST radio source counterparts as quasar candidates. This allows a qualitatively different approach of constructing a series of samples at di...

We present a catalogue of about 6 million unresolved photometric detections in the Sloan Digital Sky Survey Seventh Data Release classifying them into stars, galaxies and quasars. We use a machine learning classifier trained on a subset of spectroscopically confirmed objects from 14th to 22nd magnitude in the SDSS i-band. Our catalogue consists of 2,430,625 quasars, 3,544,036 stars and 63,586 u...

We present optical spectra and redshift measurements for 178 flat-spectrum objects from the Parkes quarter-Jansky flat-spectrum sample. These spectra were obtained in order to compile a complete sample of quasars for use in a study of quasar evolution. We present a composite optical spectrum made from the subset of 109 quasars that have flux densities in the range 0.25Jy < S2.7GHz < 0.5Jy, and ...