6 research outputs found
The FSVS Cluster Catalogue: Galaxy Clusters and Groups in the Faint Sky Variability Survey
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 = 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 accepte
Stellar populations in brightest cluster galaxies
We present the results of an investigation of a large sample of brightest cluster galaxies (BCGs), their kinematic and stellar population properties and the relationships between these and the properties of the host clusters. We have obtained high signal-to-noise, long-slit spectra of 49 BCGs in the nearby Universe with the Gemini and WHT telescopes. From this, we have measured the radial velocity and velocity dispersion profiles, and used the Lick system of absorption indices to derive Single Stellar Population (SSP)-equivalent ages, metallicities and α-abundance ratios. The results were systematically compared with those of large samples of ordinary elliptical galaxies in the same mass range. In addition, the derived properties were tested for possible correlations with the internal properties of the galaxies (mass, rotation and luminosity) and the properties of the host clusters (density, mass, distance to X-ray peak and cooling flows). We address the following questions: how the kinematic and stellar population properties differ from those of ordinary giant elliptical galaxies; and whether these properties are more influenced by the internal parameters of the BCGs or the properties of the clusters. © International Astronomical Union 2010
Influence of restricted FOV and CCD binning in SH-WFS on the performance of NAOMI
Using a unique combination of empirical data collected simultaneously by the science camera (INGRID) and the wave front sensor in NAOMI plus the same night profiles of the turbulent layers measured by SLODAR, we discuss the accuracy of the analytic approach to modelling of AO performance. The WFS frames recorded for different atmospheric conditions allow us to make a detailed investigation of the influence of a restricted field of view and sampling of the WFS on the accuracy of the centre of gravity and its propagation to the residual variance. The predictions of Strehl, FWHM and FWHE derived for NAOMI-INGRID using our analytic approach are compared with on-sky performance demonstrated during the commissioning and science observations with NAOMI