We analyze the internal velocity dispersion, σ, of a sample of 172 nearby galaxy clusters (z≤ 0.15), each of which has at least 30 available galaxy redshifts, and spans a large richness range. Cluster membership selection is based on nonparametric methods. In the estimate of galaxy velocity dispersion we consider the effects of possible velocity anisotropies in galaxy orbits, the infall of late...

The distribution of galaxies in position and velocity around the centers of galaxy clusters encodes important information about cluster mass and structure. Using the maxBCG galaxy cluster catalog identified from imaging data obtained in the Sloan Digital Sky Survey, we study the BCG–galaxy velocity correlation function. By modeling its non-Gaussianity, we measure the mean and scatter in velocit...

This paper presents quantitative techniques for studying, in an unbiased manner, the photometric and structural properties of galaxies in clusters, including a means to identify likely background objects in the absence of redshift information. We develop self-consistent and reproducible measurements of fundamental properties of galaxies such as radius, surface brightness, concentration of light...

Kaiser & Squires have proposed a technique for mapping the dark matter in galaxy clusters using the coherent weak distortion of background galaxy images caused by gravitational lensing. We investigate the effectiveness of this technique under controlled conditions by creating simulated CCD frames containing galaxies lensed by a model cluster, measuring the resulting galaxy shapes, and comparing...

ABSTRACT Counts of galaxy clusters offer a high-precision probe cosmology, but control systematic errors will determine the accuracy this measurement. Using Buzzard simulations, we quantify one such systematic, triaxiality distribution identified with redMaPPer optical cluster finding algorithm, which was used in Dark Energy Survey Year-1 (DES Y1) cosmology analysis. We test whether selection b...

A new look at globular cluster colors in NGC 3311 and the case for exclusively metal–rich globular cluster systems ABSTRACT NGC 3311, the central cD galaxy in the Hydra cluster, was previously thought to host the most metal–rich globular cluster system known. Ground–based Washington photometry had indicated the almost complete absence of the population of globu-lar clusters near [Fe/H] ∼ −1 dex...

We present results from a search to detect radio emission at 1.4 GHz from gravitationally lensed arcs towards galaxy clusters. Using the FIRST survey observations of galaxy cluster fields, we have clearly detected 1.4 GHz emission at the location of bright arc towards the galaxy cluster Abell 370. The possibility that this emission is associated with a projected galaxy superimposed on the arc c...

Gravitational lensing has now become a popular tool to measure the mass distribution of structures in the Universe on various scales. Here we focus on the study of galaxy’s scale dark matter halos with galaxy-galaxy lensing techniques: observing the shapes of distant background galaxies which have been lensed by foreground galaxies allows us to map the mass distribution of the foreground galaxi...

Context. The cosmic time around the z ∼ 1 redshift range appears crucial in the cluster and galaxy evolution, since it is probably the epoch of the first mature galaxy clusters. Our knowledge of the properties of the galaxy populations in these clusters is limited because only a handful of z ∼ 1 clusters are presently known. Aims. In this framework, we report the discovery of a z ∼ 0.87 cluster...