Search

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 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 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.

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 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.

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

On a applique le processus de Detection Automatique des Quasars a un champ contenant le pole galactique sud. On montre que les deplacements vers le rouge sont essentiels dans les etudes de regroupement et que de tres grands progres pourraient etre faits s'ils etaient obtenus a partir d'une spectroscopie a basse resolution

Les observations VLA d'un echantillon de 156 galaxies IRAS sont utilisees pour examiner en detail la correlation entre l'emission radio et l'emission IR lointain de ces galaxies

La zone contient 312 sources IRAS ponctuelles: 148 sont identifiees a des etoiles, 154 a des galaxies et 10 demeurent sans contrepartie jusqu'a la 21 e magnitude. On discute des proprietes statistiques de l'echantillon