Related papers: A QSO in a Cluster at z=2.4
We present multicolour images of the hosts of three z=2 QSOs previously detected in R-band by our group. The luminosities, colours and sizes of the hosts overlap with those of actively star-forming galaxies in the nearby Universe. Radial…
A preliminary analysis of fields around 20 mainly radio-quiet QSOs (RQQs) at intermediate redshift is summarized. We find overdensities of faint sources around 50% of our observed QSOs suggesting that they are located in groups or even…
We present tentative evidence for primordial clustering, manifested as an excess of color-selected objects in the field of the QSO SDSS J1030+0524 at redshift z=6.28. We have selected objects red in i_{775}-z_{850} on the basis of Hubble…
We report on deep imaging in 2 filters with the PC2 camera of HST, of five QSOs at redshift ~2, with a range of optical and radio luminosity. The observations included a suite of PSF observations which were used to construct new PSF models,…
High-redshift galaxy clusters, unlike local counterparts, show diverse star formation activities. However, it is still unclear what keeps some of the high-redshift clusters active in star formation. To address this issue, we performed a…
Based on an R-band imaging survey of 6 high redshift (z~2) and high luminosity (M<-28mag) QSOs, we report the detection of extensions in two radio-quiet and one radio-loud QSO. The extensions are most likely due to the host galaxies of…
We have obtained new deep optical and near-infrared images of the field of the radio-loud quasar 1335.8+2834 at $z=1.086$ where an excess in the surface number density of galaxies was reported by Hutchings et al. [AJ, 106, 1324] from…
We present an extensive photometric and spectroscopic study of two high-redshift clusters of galaxies based on data obtained from the Keck 10m telescopes and the Hubble Space Telescope. The clusters CL0023+0423 (z=0.84) and CL1604+4304…
We previously reported a significant clustering of red galaxies (R-K=3.5--6) around the radio-loud quasar B2 1335+28 at z=1.086. In this paper, we establish the existence of a rich cluster at the quasar redshift, and study the properties of…
Observed high-redshift QSOs, at z~6, may reside in massive dark matter (DM) halos of more than 10^{12} Msun and are thus expected to be surrounded by overdense regions. In a series of 10 constrained simulations, we have tested the…
Intrinsic emission and absorption lines of QSOs provide several independent probes of the metal abundances in QSO environments. They indicate that the metallicities are typically solar or higher out to redshifts z > 4. These results support…
We examine the relationship between galaxies and the intergalactic medium at z < 1 using a group of three closely spaced background QSOs with z_em ~1 observed with the Hubble Space Telescope. Using a new grouping algorithm, we identify…
Based on a cross-correlation analysis of X-ray selected QSOs with faint (B<20.5) galaxies, we find a 5sigma galaxy excess around low-redshift (z<0.3) QSOs with an amplitude identical to that of the galaxy angular correlation function. The…
It is pointed out that there are now known four very close pairs of QSOs with separations < 5 arcsec and very different redshifts. Several estimates of the probability that they are accidental configurations range between 10^{-7} and 3.5 x…
We present results of the hosts of four high-redshift ($z \approx 2$) and high luminosity ($M_B \lsim -28$ mag) QSOs, three radio-quiet one radio-loud, imaged in R and K bands. The extensions to the nuclear unresolved source are most likely…
We report the discovery of four high-redshift objects (3.3 < z < 4) observed behind the rich cluster CL0939+4713 (Abell 851). One object (DG 433) has a redshift of z=3.3453; the other three objects have redshifts of z\approx 4: A0 at…
We report the discovery of an X-ray luminous galaxy cluster at z =1.11. RDCS J0910+5422 was selected as an X-ray cluster candidate in the ROSAT Deep Cluster Survey on the basis of its spatial extent in a Rosat PSPC image. Deep optical and…
We present a detailed morphological analysis of the galaxy populations in the first two clusters to be completed in an extensive observational study of nine high-redshift clusters of galaxies (Oke, Postman & Lubin 1998). These two clusters,…
QSOs have been thought to be important for tracing highly biased regions in the early universe, from which the present-day massive galaxies and galaxy clusters formed. While overdensities of star-forming galaxies have been found around QSOs…
We report the discovery of a quasar pair at z=5 separated by 21 arcsec. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the CFHT Legacy Survey (CFHTLS). Spectra…