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We describe a large sample of 598 galaxy clusters and rich groups discovered in the data of the Faint Sky Variability Survey. The clusters have been identified using a fully automated, semi-parametric technique based on a maximum likelihood approach applied to Voronoi tessellation, and enhanced by colour discrimination. The sample covers a wide range of richness, has a density of ~28 clusters per sqdeg, and spans a range of estimated redshifts of 0.05 < z < 0.9 with mean = 0.345. Assuming the presence of a cluster red sequence, the uncertainty of the estimated cluster redshifts is assessed to be \~0.03. Containing over 100 clusters with z > 0.6, the catalogue contributes substantially to the current total of optically-selected, intermediate-redshift clusters, and complements the existing, usually X-ray selected, samples. The FSVS fields are accessible for observation throughout the whole year, making them particularly suited for large follow-up programmes. The construction of this FSVS Cluster Catalogue completes a fundamental component of our continuing programmes to investigate the environments of quasars and the chemical evolution of galaxies. We publish here the list of all clusters with their basic parameters, and discuss some illustrative examples in more detail. The full FSVS Cluster Catalogue, together with images and lists of member galaxies etc., will be issued as part of the ``NOAO data products'', and accessible at http://www.noao.edu/dpp/. We describe the format of these data and access to them., Comment: 19 pages and 17 figures, MNRAS accepted

We report the finding of two large-scale structures of galaxies in a 40'x35' field embedded in a 25deg^2 area where two 100 Mpc-scale structures of quasars and MgII absorbers at z~0.8 and z~1.2 have been previously detected. Using deep optical (V- and I-band) imaging, we are able to select high-redshift (0.5

We report on the discovery of two new faint cataclysmic variables. The objects were selected as candidates from two different imaging surveys aimed at the discovery of such faint systems. One survey used color and variability while the other used color and H$_\alpha$ emission as selection criteria. We present our spectra of the two new variables and discuss their properties. A discussion of the implication of these discoveries on the space density of faint cataclysmic variables is presented., Comment: 4 pages, 4 figures. Accepted to A&A letters

The largest known structure in the high redshift universe is mapped by at least 18 quasars and spans ~5 deg x 2.5 deg on the sky, with a quasar spatial overdensity of 6-10 times above the mean. This large quasar group provides an extraordinary laboratory ~100 x 200 x 200 h^-3 comoving Mpc^3 in size (q0=0.5, Lambda=0, H0=100h km/s/Mpc) covering 1.20

We are looking at quasar environment in the context of large-scale structure (LSS) - a new approach, giving a more informed interpretation of quasar-galaxy correlations. This paper presents our first results for a sample of z ~ 0.3 quasars. We are using Voronoi tessellation applied in colour (B_J - R) slices for the detection of galaxy clusters and the minimal spanning tree (MST) to delineate the large-scale structure. This new cluster-detection method allows us to find reliably galaxy clusters at z < 0.3 from SuperCOSMOS measurements of UK Schmidt plates. By reconstructing the large-scale structure in a relatively narrow redshift band (0.2 < z < 0.3), we show that quasars follow the large-scale structure traced by galaxy clusters. None of the quasars in our radio-quiet sample is located in the central area of a galaxy cluster. Two quasars, found in a very rich environment, are actually located between two very close galaxy clusters, consistent with results on z ~ 1 quasars suggesting that cluster merg ers may be involved in one of the quasar formation mechanisms., Comment: 9 pages, Latex, 7 figures, MNRAS accepted for publication

The Clowes-Campusano Large Quasar Group (LQG) is the largest known structure at high redshifts, with at least 18 quasars at z~1.3 forming a structure ~200 Mpc across. We are conducting an ultra-deep optical and deep NIR study to examine the galaxy environment of quasars in this LQG to determine if, and how, LQGs trace large-scale structure at early epochs. We report significant associated clustering in the field of a z=1.226 quasar from this LQG in the form of a factor ~11 overdensity of I-K>3.75 galaxies, and red sequences of 15-18 galaxies at I-K~4.3,V-K~6.9, indicative of a population of massive ellipticals at the quasar redshift. The quasar is located between two groups of these galaxies, with further clustering extending over 2-3 Mpc. Within 30 arcsec of the quasar we find a concentration of blue (V-I<1) galaxies in a band that bisects the two groups of red sequence galaxies. This band is presumed to correspond to a region of enhanced star-formation. We suggest that the merging of the two groups of red sequence galaxies has triggered both the quasar and the band of star-formation. Quasars at z~1.3 are located in a variety of environments, but those with associated clustering are found on the cluster peripheries., Comment: 6 pages, 3 figures, uses newpasp.sty. To appear in the proceedings of "The New Era of Wide-Field Astronomy", Preston, UK, August 2000. A version of the poster also presented at this conference is available at http://www.star.uclan.ac.uk/~cph/poster.html

We have conducted ultra-deep optical and deep near-infrared observations of a field around the z=1.226 radio-quiet quasar 104420.8+055739 from the Clowes-Campusano LQG of 18 quasars at z~1.3 in search of associated galaxy clustering. Galaxies at these redshifts are distinguished by their extremely-red colours, with I-K>3.75, and we find a factor ~11 overdensity of such galaxies in a 2.25'x2.25' field centred on the quasar. In particular, we find 15-18 galaxies with colours consistent with being a population of passively-evolving massive ellipticals at the quasar redshift. They form `fingers' in the V-K/K, I-K/K colour-magnitude plots at V-K~6.9, I-K~4.3 comparable to the red sequences observed in other z~1.2 clusters. We find suggestive evidence for substructure among the red sequence galaxies in the K image, in the form of two compact groups, 40 arcsec to the north, and 60 arcsec to the south-east of the quasar. An examination of the wider optical images indicates that this substructure is significant, and that the clustering extends to form a large-scale structure 2-3 Mpc across. We find evidence for a high (>50%) fraction of blue galaxies in this system, in the form of 15-20 `red-outlier' galaxies with I-K>3.75 and V-I<2.00, which we suggest are dusty, star-forming galaxies at the quasar redshift. Within 30 arcsec of the quasar we find a concentration of blue (V-I<1) galaxies in a band that bisects the two groups of red sequence galaxies. This band of blue galaxies is presumed to correspond to a region of enhanced star-formation. We explain this distribution of galaxies as the early-stages of a cluster merger which has triggered both the star-formation and the quasar., Comment: 12 pages, 8 figures. Accepted for publication in MNRAS. A VIK three-colour image of the 2.25'x2.25' quasar field is available at http://www.star.uclan.ac.uk/~cph/images/rgb.jpg

We report significant associated clustering in the field of a z=1.226 quasar from the Clowes-Campusano LQG in the form of both a factor ~11 overdensity of I-K>3.75 galaxies and red sequences of 15-18 galaxies at I-K~4.3, V-K~6.9 indicative of a population of massive ellipticals at the quasar redshift. The quasar is located between two groups of these galaxies, with further clustering extending over 2-3 Mpc. A band of V-I<1 galaxies bisects the two groups of red sequence galaxies, and we suggest that the merging of these two groups has triggered both this band of star-formation and the quasar., Comment: 2 pages, 1 figure, uses newpasp.sty. To appear in the proceedings of IAU Symposium 201, "New Cosmological Data and the Values of the Fundamental Parameters", August 2000, eds. A. Lasenby, A. Wilkinson

We apply a simple statistical method (Derenzo & Hildebrand 1969) to estimating the completeness of quasar surveys. It requires that an area has been covered by two or more, preferably different, selection techniques. We use three suitable data sets with separate selections from: variability and UV-excess (170 quasars); objective prism and UV-excess (141 quasars); multicolour and X-ray ({\it ROSAT,} 19 quasars). We find that, for selection by UV-excess, the common limit of $U-B \le -0.35 \pm -0.05$ leads to losses of $\sim 35%$, typically missing low-luminosity $(M_{B} \gtrsim -24.5)$ quasars, independently of redshift. Systematic incompleteness will therefore affect the new generation of large quasar surveys that select by $U-B \le -0.35$. By correcting for this incompleteness, we find, from the first data set ($B < 21.0$ and $z < 2.2$), that the evolution of the quasar luminosity function (LF) is best described by joint luminosity and density evolution. When extrapolated to $z = 0$, the LF matches that of local Seyfert galaxies better than any previous determination. The LF shows an increase in the number of low-luminosity quasars at low redshifts and of brighter quasars at intermediate redshifts, relative to the LF of Boyle et al. (1990). This result is consistent with models in which quasars fade from an initial bright phase., Comment: 22 pages, 2 figures, to appear in ApJ

The Chile-UK quasar survey, a new-generation 140 deg^2 UVX survey to B = 20, is now \sim 25 per cent complete. The catalogue currently contains 319 quasars and 93 emission line galaxies. Using the minimal-spanning tree method, we have independently confirmed the \sim 200 h^-1 Mpc group of quasars at z \simeq 1.3 discovered by Clowes & Campusano (1991). We have discovered a new \sim 150 h^-1 Mpc group of 13 quasars at median z \simeq 1.51. The null hypothesis of a uniform, random distribution is rejected at a level of significance of 0.003 for both groups., Comment: 2 pages including 2 figures, Latex, sprocl.sty and psfig.sty included. To appear in proceedings of the 12th Potsdam Cosmology Workshop 1997. Larger versions of the figures are available from p.r.newman@uclan.ac.uk

This is the first paper in a series aimed at defining a statistically significant sample of QSOs in the range $ 15 < B < 18.75$ and $ 0.3 < z < 2.2$. The selection is carried out using direct plates obtained at the ESO and UK Schmidt Telescopes, scanned with the COSMOS facility and searched for objects with an ultraviolet excess. Follow-up spectroscopy, carried out at ESO La Silla, is used to classify each candidate. In this initial paper, we describe the scientific objectives of the survey; the selection and observing techniques used. We present the first sample of 285 QSOs ($M_B < -23$) in a 153 deg$^2$ area, covered by the six ``deep'' fields, intended to obtain significant statistics down $B \simeq 18.75$ with unprecedented photometric accuracy. From this database, QSO counts are determined in the magnitude range $ 17 < B < 18.75$., Comment: 21 pages uuencoded compressed postscript, to appear in Astronomy and Astrophysics Supplements, 1995