Search

Correlated orientations of quasar optical and radio polarisation, and of radio jets, have been reported on Gpc scales, possibly arising from intrinsic alignment of spin axes. Optical quasar polarisation appears to be preferentially either aligned or orthogonal to the host large-scale structure, specifically large quasar groups (LQGs). Using a sample of 71 LQGs at redshifts $1.0 \leq z \leq 1.8$, we investigate whether LQGs themselves exhibit correlated orientation. We find that LQG position angles (PAs) are unlikely to be drawn from a uniform distribution ($p$-values $0.008 \lesssim p \lesssim 0.07$). The LQG PA distribution is bimodal, with median modes at $\bar{\theta}\sim45\pm2^{\circ}, 136\pm2^{\circ}$, remarkably close to the mean angles of quasar radio polarisation reported in two regions coincident with our LQG sample. We quantify the degree of alignment in the PA data, and find that LQGs are aligned and orthogonal across very large scales. The maximum significance is $\simeq 0.8\%$ ($2.4\sigma$) at typical angular (proper) separations of $\sim 30^{\circ}$ (1.6 Gpc). If the LQG orientation correlation is real, it represents large-scale structure alignment over scales larger than those predicted by cosmological simulations and at least an order of magnitude larger than any so far observed, with the exception of quasar-polarisation / radio-jet alignment. We conclude that LQG alignment helps explain quasar-polarisation / radio-jet alignment, but raises challenging questions about the origin of the LQG correlation and the assumptions of the concordance cosmological model., Comment: Accepted for MNRAS

We present the serendipitous discovery of a `Giant Arc on the Sky' at $z \sim 0.8$. The Giant Arc (GA) spans $\sim 1$ Gpc (proper size, present epoch), and appears to be almost symmetrical on the sky. It was discovered via intervening MgII absorbers in the spectra of background quasars, using the catalogues of Zhu \& M\'enard. The use of MgII absorbers represents a new approach to the investigation of large-scale structures (LSSs) at redshifts $0.45 \lesssim z \lesssim 2.25$. We present the observational properties of the GA, and we assess it statistically using methods based on: (i) single-linkage hierarchical clustering ($\sim 4.5\sigma$); (ii) the Cuzick-Edwards test ($\sim 3.0\sigma$); and (iii) power spectrum analysis ($\sim 4.8\sigma$). Each of these methods has distinctive attributes and powers, and we advise considering the evidence from the ensemble. We discuss our approaches to mitigating any {\it post-hoc} aspects of analysing significance after discovery. The overdensity of the GA is $\delta \rho / \rho \sim 1.3 \pm 0.3$. The GA is the newest and one of the largest of a steadily accumulating set of very large LSSs that may (cautiously) challenge the Cosmological Principle, upon which the `standard model' of cosmology is founded. Conceivably, the GA is the precursor of a structure like the Sloan Great Wall (but the GA is about twice the size), seen when the Universe was about half its present age., Comment: Accepted for MNRAS

Evidence presented by Yershov, Orlov and Raikov apparently showed that the WMAP/Planck cosmic microwave background (CMB) pixel-temperatures (T) at supernovae (SNe) locations tend to increase with increasing redshift ($z$). They suggest this correlation could be caused by the Integrated Sachs-Wolfe effect and/or by some unrelated foreground emission. Here, we assess this correlation independently using Planck 2015 SMICA R2.01 data and, following Yershov et al., a sample of 2783 SNe from the Sternberg Astronomical Institute. Our analysis supports the prima facie existence of the correlation but attributes it to a composite selection bias (high CMB T $\times$ high SNe $z$) caused by the accidental alignment of seven deep survey fields with CMB hotspots. These seven fields contain 9.2 per cent of the SNe sample (256 SNe). Spearman's rank-order correlation coefficient indicates the correlation present in the whole sample ($\rho_s = 0.5$, p-value $= 6.7 \times 10^{-9}$) is insignificant for a sub-sample of the seven fields together ($\rho_s = 0.2$, p-value $= 0.2$) and entirely absent for the remainder of the SNe ($\rho_s = 0.1$, p-value $= 0.6$). We demonstrate the temperature and redshift biases of these seven deep fields, and estimate the likelihood of their falling on CMB hotspots by chance is at least $\sim$ 6.8 per cent (approximately 1 in 15). We show that a sample of 7880 SNe from the Open Supernova Catalogue exhibits the same effect and we conclude that the correlation is an accidental but not unlikely selection bias., Comment: 12 pages, 6 figures, 7 tables (+ appendices: 7 pages, 8 figures, 1 table), accepted for publication in MNRAS

We investigate the strength of ultraviolet Fe II emission in fainter quasars compared with brighter quasars for 1.0 ~ 25 Ang. there is a universal (i.e. for quasars in general) strengthening of W2400 with decreasing intrinsic luminosity, L3000. (2) In conjunction with previous work by Clowes et al., we find that there is a further, differential, strengthening of W2400 with decreasing L3000 for those quasars that are members of Large Quasar Groups (LQGs). (3) We find that increasingly strong W2400 tends to be associated with decreasing FWHM of the neighbouring Mg II {\lambda}2798 broad emission line. (4) We suggest that the dependence of W2400 on L3000 arises from Ly{\alpha} fluorescence. (5) We find that stronger W2400 tends to be associated with smaller virial estimates from Shen et al. of the mass of the central black hole, by a factor ~ 2 between the ultrastrong emitters and the weak. Stronger W2400 emission would correspond to smaller black holes that are still growing. The differential effect for LQG members might then arise from preferentially younger quasars in the LQG environments., Comment: Accepted for publication in MNRAS. 21 pages, 11 figures

This paper describes an algorithm based on the 2D approach of Allard and Fraley that uses Voronoi tessellation and a non-parametric maximum likelihood estimator. We have designed a 3D version of this algorithm which detects multiple clusters of points immersed in background noise; its application to the detection of galaxy clusters in redshift space, using the astronomical database of the 2-degree Field Galaxy Redshift Survey, is presented and discussed. Adopting as a benchmark a particular set of catalogued clusters of galaxies, we find that the proposed algorithm recognizes the location of ∼ 67% of the clusters. Three variants of the algorithm were assessed to deal with the elongation of the clusters in the radial direction of observation introduced by the astronomical distance indicator; their merits and limitations are discussed. We address separately the detection of the galaxy cluster location and the detection of galaxy cluster members, both of them having an anisotropic space as their search domain. In the case of detection of galaxy cluster members, a second stage of detection was incorporated in order to improve the results. © 2006 IEEE.

A Large Quasar Group (LQG) of particularly large size and high membership has been identified in the DR7QSO catalogue of the Sloan Digital Sky Survey. It has characteristic size (volume^1/3) ~ 500 Mpc (proper size, present epoch), longest dimension ~ 1240 Mpc, membership of 73 quasars, and mean redshift = 1.27. In terms of both size and membership it is the most extreme LQG found in the DR7QSO catalogue for the redshift range 1.0, Accepted for publication in Monthly Notices of the Royal Astronomical Society. 9 pages, 3 figures

We investigate whether radio-quiet quasars (RQQs) with z < 0.3 (and predominantly of low luminosity) are located preferentially in specific regions with respect to the centres and boundaries of neighbouring galaxy clusters. This way of characterizing the environment of RQQs differs from previous studies, which relied on the galaxy excess statistics within small radii around the quasars. For the detection of galaxy clusters we use a robust, semiparametric method based on a maximum likelihood estimate applied to Voronoi tessellation and enhanced by a colour-cut approach, allowing boundary determination and redshift estimates. We find that most of the RQQs reside within 3 h -1 Mpc of the centre of a galaxy cluster with comparable redshift and that none of them lies in the core itself. About 20 per cent of the investigated quasars reside between two galaxy clusters, which are possibly at an early stage of merger. Consequently, we suggest that quasars found in rich environments are associated with cluster mergers whereas those found in poorer environments are associated with infall towards a cluster. The information on larger scales provided by our analysis thus allows a clearer interpretation of the diverse environments that have for many years been reported in the literature for smaller scales. We discuss our findings in the context of existing quasar formation models and suggest that at least two formation mechanisms coexist. Additionally, we confirm, using multiple data sets, that low-redshift quasars follow a narrow channel of width ∼10 h -1 Mpc around the large-scale structure (LSS) traced by galaxy clusters, in agreement with the first report of this effect by Söchting, Clowes and Campusano. Such a result, if it applies to quasars at higher redshifts, has the potential to explain the clustering of quasars on scales

This paper presents a large sample of intermediate- to high-redshift galaxy groups and clusters detected using a fully automated search in the Cosmic Evolution Survey field. The detection algorithm is based on density peak extraction from a density distribution sampled using Voronoi tessellation within overlapping slices in the photometric redshift space. The cluster catalogue contains 1780 structures covering the redshift range 0.2 0.4 and many even below this threshold show very prominent substructure indicating that z~ 0.4 marks the slow emergence of virialized clusters in this field in agreement with published findings for other regions of the sky. The redshift distribution of detected structures shows strong variations with prominent peaks suggesting the presence of large-scale structures across the whole range covered by this catalogue. Supercluster candidates have been identified at redshifts z= 0.35, 0.72, 0.94, 1.12, 1.27, 1.45, 2.0 and 2.52. At z= 2.9 we identified a compact agglomeration of galaxy groups and clusters suggesting the presence of another supercluster-like structure which has been the highest redshift candidate so far. Out of the nine supercluster candidates found in this study, six are new detections. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

The Clowes & Campusano (1991) Large Quasar Group (LQG) at = 1.28 has been re-examined using the quasar data from the DR7QSO catalogue of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR7QSO data, the western, northern and southern boundaries of the LQG remain essentially the same, but an extension eastwards of \sim 2 deg is indicated. In the DR7QSO data, the LQG has 34 members, with = 1.28. A new group of 38 members is indicated at = 1.11 and within \sim 2.0 deg of the Clowes & Campusano LQG. The characteristic sizes of these two LQGs, \sim 350-400 Mpc, appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology. In addition to their intrinsic interest, these two LQGs provide locations in which to investigate early large-scale structure in galaxies and to identify high-z clusters. A method is presented for assessing the statistical significance and overdensity of groups found by linkage of points.

We identify 1901 galaxy clusters (N g ≥ 2) with the VoML+G algorithm (Paper I) on the Two-Degree Field Galaxy Redshift Survey. We present the 341 clusters with at least 10 galaxies that are within 0.009 < z < 0.14 (the Catalog), of which 254 (~75%) have counterparts in the literature (NED), with the remainder (87) plausibly "new" because of incompleteness of previous searches or unusual galaxy contents. The 207 clusters within z = 0.04–0.09 are used to study the properties of the galaxy systems in the nearby universe, including their galaxy contents parameterized by the late-type galaxy fractions (f L ). For this nearly complete cluster subsample, we find the following: (i) 63% are dominated by early-type galaxies (i.e., the late-type-poor clusters, f L < 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 22 ± 1 and 12.91 ± 0.04, respectively; and (ii) 37% are dominated by late-type galaxies (i.e., the late-type-rich clusters, f L ≥ 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 15.7 ± 0.9 and 12.66 ± 0.07, respectively. The statistical analysis of the late-type fraction distribution supports, with a 3σ confidence level, the presence of two population components. It is suggested that the late-type-poor galaxy systems reflect and extend the class of Abell-APM-EDCC clusters and that the late-type-rich systems (~one-third of the total) belong to a new, previously unappreciated class. The late-type-rich clusters, on average high mass-to-light ratio systems, appear to be more clustered on large scales than the late-type-poor clusters. A class of late-type-rich clusters is not predicted by current theory.

We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the twelfth data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0$\sigma$ level respectively for the two lines of the doublet. The catalogue was constrained to an absorption line redshift of 0.35 $\le$ z$_{2796}$ $\le$ 2.3. The rest-frame equivalent width of the $\lambda$2796 line ranges between 0.2 $\le$ W$_r$ $\le$ 6.2 $\AA$. Using Gaussian-noise only simulations we estimate a false positive rate of 7.7 per cent in the catalogue. We measured the number density $\partial N^{2796}/\partial z$ of Mg II absorbers and find evidence for steeper evolution of the systems with W$_r \ge$ 1.2 $\AA$ at low redshifts (z$_{2796}$ $\le$ 1.0), consistent with other earlier studies. A suite of null tests over the redshift range 0.5 $\le$ z$_{2796}$ $\le$ 1.5 was used to study the presence of systematics and selection effects like the dependence of the number density evolution of the absorption systems on the properties of the background quasar spectra. The null tests do not indicate the presence of any selection effects in the absorption catalogue if the quasars with spectral signal-to-noise level less than 5.0 are removed. The resultant catalogue contains 36,981 absorption systems. The Mg II absorption catalogue is publicly available and can be downloaded from the link http://srini.ph.unimelb.edu.au/mgii.php, Comment: Updated references, typos; Published in MNRAS; 15 pages, 14 figures, 2 tables

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., 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

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 usingVoronoitessellation applied in colour (B J −R) slices for the detection of galaxyclustersand the minimal spanning tree (MST) to delineate the large-scale structure. This newcluster-detection method allows us to find reliably galaxy clusters at z < 0.3 fromSuperCOSMOS measurements of UK Schmidt plates. By reconstructing the large-scale structure in a relatively narrow redshift band (0.2 < z < 0.3), we show thatquasars follow the large-scale structure traced by galaxy clusters. None of the quasarsin ourradio-quiet sample is located in the central areaofa galaxycluster. Two quasars,found in a very rich environment, are actually located between two very close galaxyclusters, consistent with results on z ∼ 1 quasars suggesting that cluster mergers maybe involved in one of the quasar formation mechanisms.Key words: galaxies: clusters: general – quasars: general – cosmology: large-scalestructure of Universe.

This paper is the first in a series, presenting a new galaxy cluster finder based on a three-dimensional Voronoi Tesselation plus a maximum likelihood estimator, followed by gapping-filtering in radial velocity(VoML+G). The scientific aim of the series is a reassessment of the diversity of optical clusters in the local universe. A mock galaxy database mimicking the southern strip of the magnitude(blue)-limited 2dF Galaxy Redshift Survey (2dFGRS), for the redshift range 0.009 < z < 0.22, is built on the basis of the Millennium Simulation of the LCDM cosmology and a reference catalog of "Millennium clusters," spannning across the 1.0 × 1012–1.0 × 1015 M ⊙ h −1 dark matter (DM) halo mass range, is recorded. The validation of VoML+G is performed through its application to the mock data and the ensuing determination of the completeness and purity of the cluster detections by comparison with the reference catalog. The execution of VoML+G over the 2dFGRS mock data identified 1614 clusters, 22% with N g ≥ 10, 64 percent with 10 > N g ≥ 5, and 14% with N g < 5. The ensemble of VoML+G clusters has a ~59% completeness and a ~66% purity, whereas the subsample with N g ≥ 10, to z ~ 0.14, has greatly improved mean rates of ~75% and ~90%, respectively. The VoML+G cluster velocity dispersions are found to be compatible with those corresponding to "Millennium clusters" over the 300–1000 km s−1 interval, i.e., for cluster halo masses in excess of ~3.0 × 1013 M ⊙ h −1.

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, 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 present the spectra and redshifts of 62 quasars, from observations made with the Cerro Tololo Inter-American Observatory (CTIO) 4-m Blanco Telescope. These quasars form part of a total sample of 118 (with 56 having been published previously), which is being used for analysis of structure in the early universe. Quasars of particular interest are noted, including eight broad absorption line (BAL) quasars and two quasars with unusual emission spectra. Finally, we include a short summary of the present status of the large quasar group (LQG) that was discovered by Clowes & Campusano from the earlier observations. The quasars are from an area∼25.3 deg2 of ESO/SERC field 927, which is centred at (1950) 10h40m00s, 05°00′00′′.

We have investigated the strength of ultraviolet Fe II emission from quasars within the environments of Large Quasar Groups (LQGs) in comparison with quasars elsewhere, for 1.1 = 45 Ang. (more precisely, ultrastrong-plus with W2400 >= 44 Ang.) have preferred nearest-neighbour separations of ~ 30-50 Mpc to the adjacent quasar of any W2400 strength. No such effect is seen for the ultrastrong emitters that are not in LQGs. The possibilities for increasing the strength of the Fe II emission appear to be iron abundance, Ly-alpha fluorescence, and microturbulence, and probably all of these operate. The dense environment of the LQGs may have led to an increased rate of star formation and an enhanced abundance of iron in the nuclei of galaxies. Similarly the dense environment may have led to more active blackholes and increased Ly-alpha fluorescence. The preferred nearest-neighbour separation for the stronger emitters would appear to suggest a dynamical component, such as microturbulence. In one particular LQG, the Huge-LQG (the largest structure known in the early universe), six of the seven strongest emitters very obviously form three pairings within the total of 73 members., Accepted for publication in Monthly Notices of the Royal Astronomical Society. 11 pages, 7 figures

The Automated Quasar Detection (AQD) technique has been applied to six connected fields near the South Galactic Pole. A comparison with the Veron & Veron catalogue (1993) and the Cristiani et al. compilation (1995) shows that AQD re–discovered % of the known quasars with non–overlapping objective–prism spectra present in these fields (% if only the high probability candidates are considered). A list of the 1592 high probability candidates is given, including the results of cross–correlation with X–ray and radio catalogues.

We present the spectroscopic observations of 56 quasars that were discovered by AQD (Automated Quasar Detection) in a field of ∼25.3 deg 2 , centred at (1950) RA 10 h 40 m 00 s , Dec. 05°00'00″. These observations, with the CTIO 4-m telescope, led to the discovery by Clowes & Campusano of a large group of quasars with size ∼100-200 h −1 Mpc at z∼1.3. Quasars of particular interest are noted, including one that is a BAL quasar with z∼1.78

Evidence for large, elongated group of at least ten quasars with largest dimension ∼ 100-200 h -1 Mpc at z ∼ 1.3, in the direction of ESO/SERC field 927, which has the field centre (1950) 10 h 40 m 00 s, 05° 00' 00″, are presented. There are probably further members that have not yet been observed. The morphology of the group seems to be like a clump, but there might be some sub-grouping on scales ∼ 20 h -1 Mpc.

Optical identifications are presented for 66 IRAS point sources in the region of the Fornax cluster of galaxies, 106 IRAS point sources in the region of the Hydra I cluster of galaxies, and 59 IRAS point sources in the region of the Coma cluster of galaxies.

A search for quasars is being performed in ESO/SERC fields 86, 119, and 120 at and near the South Ecliptic Pole (just outside the LMC). This area will be extensively covered by the ROSAT all-sky soft X-ray survey. The present search aims at providing a data base of optically selected extragalactic objects which may later be compared with the sample of X-ray selected objects. The quasar candidates were identified on objective prism plates from the UK Schmidt telescope (UKSTU) by visual means in field 86 and by employing Automated Quasar Detection (AQD) in fields 119 and 120. Slit spectra were subsequently obtained for 39 candidates in field 119 and 3 candidates in field 86, using the ESO/MPI 2.2 m telescope at La Silla, Chile. The results demonstrate that an automated quasar search can be successfully be performed in these comparatively crowded star fields.

Radio maps, spectra and CCD images have been obtained for almost all the 158 objects in a complete sample of IRAS galaxies. The linear relation between radio and far-infrared luminosity is valid over the complete luminosity range (up to LIR=1.8×1012 L⊙, H○=75 km s−1 Mpc−1). The majority of the 10 most luminous galaxies show evidence of tidal disruption and have companion galaxies at projected separations which range between 6 and 138 kpc. The second most luminous galaxy, IRAS 00275-2859, is a quasar with a spectrum reminiscent of a broad line absorption quasar and with a band of absorption running across the object: its infrared to radio luminosity ratio is identical to that of the typical IRAS galaxy.

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, Comment: 56 pages with 8 encapulated Postscript files, 6 JPEG files, with clarified graphics and statistics, aastex Latex, accepted by ApJ

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., 22 pages, 2 figures, to appear in ApJ

We report the discovery of Q1044+0546 (M V > −27), whose optical spectrum is dominated by one very strong (W(rest)~110 A) and extraordinarily broad (FWZI(rest)~270A) emission line. We argue that this line is Ly-α at z=2.688, imparting a unique character to this object because the CIV λ1549A emission line which would be around λ5700A, is weak or absent. We present a preliminary interpretation of this QSO discovered as part of our redshift program in the ESO/SERC field no. 927. The rest-frame Ly-α FWHM and FWZI are ≈ 23.000 and ≈ 67.000 km s−1, respectively; these values are among the largest found to date. A heavy element absorption line system is present too, with z=2.654, implying a relative velocity with respect to the QSO of ~ 2700 km s−1. There are also several weaker absorption lines in the blueward region of the Ly-α emission, which are presumably from the Ly-α forest. The emission spectrum of Q1044+0546 may be indicative of very special physical conditions and/or rather high metal abundances in its broad line formation region(BLR). It is of great interest to determine if the physical conditions in the clouds of its associated absorption system are also peculiar, because similarities with the BLR would favour the intrinsic hypothesis for the origin of the z abs ≈ z em systems (see Petitjean et al. 1994).

A short summary of the large groups of quasars is given, with particular emphasis on the most recent discovery — a group with a long dimension of ∼ 100–200h -1 Mpc. This group was discovered with an automated (AQD) survey for quasars, using COSMOS data of an objective-prism plate from the UK Schmidt Telescope.

In undertaking a large shallow survey for quasars, we considered especially two issues: (I) On the one hand, the shape of the Luminosity Function and the determination of the form of evolution as L ∝ (1 + z) k or L ∝ e T/τ are uncertain. Trends of this form, potentially telling about the mechanism to fuel the central engine (in principle they can reveal if the QSO phenomenon is driven by the surrounding environment or is determined by its nuclear conditions only), can be spuriously favoured by fits that overlook the observational biases. To probe the real trend, not only the database at faint magnitudes and higher redshifts has to be enlarged, but also the incompleteness at bright magnitudes should be bound or removed with better samples allowing an adequately sophisticated analysis.

A search for intermediate-redshift quasars has been carried out with slitless spectroscopy in the central 21.07 deg2 of the SA 94.

On a obtenu les spectres fentes pour un ensemble heterogene de 126 candidats quasars. Cent huit des candidats sont confirmes comme etant des quasars. On donne 45 deplacements vers le rouge nouveaux

On decrit la nouvelle technique de detection automatisee des quasars (DAQ). Avec la DAQ les effets de selection sont connus, predefinis et maintenus et de grands echantillons complets peuvent etre obtenus a partir de nombreuses plaques. On demontre le succes de la DAQ par comparaison avec une bande de 3,95×0,99 deg 2 qui a deja ete completement etudiee. La densite de surface des candidats quasars dans cette zone a ete substantiellement accrue