Related papers: A Multiwavelength Study of Binary Quasars and Thei…

From optical spectroscopy of X-ray sources observed as part of ChaMP, we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow up using the FLWO, SAAO, WIYN, CTIO, KPNO, Magellan,…

X-ray and optical observations of quadruply lensed quasars can provide a microarcsecond probe of the lensed quasar, corresponding to scale sizes of \~10^2-10^4 gravitational radii of the central black hole. This high angular resolution is…

Little is known about the statistics of gravitationally lensed quasars at large (7''-30'') image separations, which probe masses on the scale of galaxy clusters. We have carried out a survey for gravitationally-lensed objects, among sources…

We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates to g=21 from 2099 deg^2 of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191 (97.6%)…

We test the hypothesis whether high redshift QSOs would preferentially appear in small groups or pairs, and if they are associated with massive, young clusters. We carried out a photometric search for \Ly emitters on scales $\lesssim 10…

We present Chandra and Spitzer data of the 186, extragalactic, hard 2-10 keV X-ray selected sources, which lie in the central part of the Chandra Deep Field South (CDFS). For the vast majority of sources (99.5%) there is a spectroscopic or…

We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. Twelve of twenty quasar jets are detected in 5 ks ACIS-S exposures. The…

We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (z=1.695) from January 2006 to January 2007. We fit simulated point spread functions to the…

Using the 2MASS Second Incremental Data Release, we have searched for near infrared counterparts to 13214 quasars from the Veron-Cetty & Veron(2000) catalog. We have detected counterparts within 4 arcsec for 2277 of the approximately 6320…

With its excellent spatial resolution, low background, and hard-band response, the Chandra X-ray Observatory is ideal for performing exploratory surveys. These efficient, sensitive observations can place constraints on fundamental…

We present the results from exploratory Chandra observations of nine high-z (z=4.1-4.5) optically selected quasars. These quasars, taken from the DPOSS, are among the optically most luminous z>4 quasars known (M_B=-28.4 to -30.2). All have…

We report on Chandra observations of a sample of 11 optically luminous (Mb<-28.5) quasars at z=3.96-4.55 selected from the Palomar Digital Sky Survey and the Automatic Plate Measuring Facility Survey. These are among the most luminous z>4…

We present quasi-simultaneous multi-colour optical/near-IR photometry for 157 radio selected quasars, forming an unbiassed sub-sample of the Parkes Flat-Spectrum Sample. Data are also presented for 12 optically selected QSOs, drawn from the…

Quasars are effective tracers of the large-scale distribution of galaxies at high redshift thanks to their high luminosity and dedicated surveys. Previous studies have shown that quasars exhibit a bias similar to that of rich groups,…

Context: The INTEGRAL hard X-ray observatory has revealed an emerging population of highly obscured X-ray binary systems through multi-wavelength observations. Previous studies have shown that many of these sources are high-mass X-ray…

We report on our search for distant clusters of galaxies based on optical and X-ray follow up observations of X-ray candidates from the SHARC survey. Based on the assumption that the absence of bright optical or radio counterparts to…

We present the results obtained from exploratory Chandra observations of nine high-redshift (z=4.09-4.51) quasars, selected from among the optically brightest Palomar Digital Sky Survey quasars known. Their broad-band spectral energy…

We have analyzed images from the VST ATLAS survey to identify candidate gravitationally lensed quasar systems in a sample of WISE sources with W1 - W2 > 0.7. Results from followup spectroscopy with the Baade 6.5 m telescope are presented…

This paper presents XMM-Newton and Chandra X-ray spectroscopy of ten flat-spectrum radio quasars (FSRQ) which are candidates to have an X-ray spectrum dominated by jet synchrotron emission. In all these FSRQ, which are less strongly…

Quasars at early redshifts ($z > 6$) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416$-$21.2339, a $z=6.23$…