ﻻ يوجد ملخص باللغة العربية
We analyse the spatial distribution and colour of the intracluster light (ICL) in 683 clusters of galaxies between z=0.2 and 0.3, selected from approx 1500 deg^2 of the SDSS-DR1. Surface photometry in the g, r and i bands is conducted on stacked images of the clusters, after rescaling them to the same metric size and masking out resolved sources. We are able to trace the average surface brightness profile of the ICL out to 700 kpc, where it is less than 1/10,000 of the mean surface brightness of the dark night sky. The ICL appears as a clear surface brightness excess with respect to an inner R^1/4 profile which characterises the mean profile of the BCG. The surface brightness (SB) of the ICL ranges from 27.5 mag/arcsec^2 at 100 kpc to roughly 32 at 700 kpc in the observed r-band (26.5 to 31 in the rest-frame g-band). We find that, on average, the ICL contributes only a small fraction of the total optical emission in a cluster (10.9+-5.0% within 500 kpc). The radial distribution of the ICL is more centrally concentrated than that of the cluster galaxies, but the colours of the two components are identical within the statistical uncertainties. In the mean the ICL is aligned with and more flattened than the BCG itself. This alignment is substantially stronger than that of the cluster light as a whole. The SB of the ICL correlates both with BCG luminosity and with cluster richness, while the fraction of the total light in the ICL is almost independent of these quantities. These results support the idea that the ICL is produced by stripping and disruption of galaxies as they pass through the central regions of clusters. Our measurements of the diffuse light also constrain the faint-end slope of the cluster LF. Slopes alpha<-1.35 would imply more light from undetected galaxies than is observed in the diffuse component.
We investigate the Sloan Digital Sky Survey (SDSS) photometry from Data Release 8 (DR8) in the search for systematic trends that still exist after the calibration effort of Padmanabhan et al. We consider both the aperture and point-spread function (P
We study the optical colors of 147,920 galaxies brighter than g* = 21, observed in five bands by the Sloan Digital Sky Survey (SDSS) over ~100 sq. deg. of high Galactic latitude sky along the Celestial Equator. The distribution of galaxies in the g*-
We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 <= z <= 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of o
We present a catalog of galaxy clusters selected using the maxBCG redsequence method from Sloan Digital Sky Survey photometric data. This catalog includes 13,823 clusters with velocity dispersions greater than 400 km/s, and is the largest galaxy clus
We study the stellar populations of SNe Ia host galaxies using SDSS-II spectroscopy. We focus on the relationships of SNe Ia properties with stellar velocity dispersion and the stellar population parameters age, metallicity and element abundance rati