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We re-examine the existence and extent of the planar structure in the local galaxy density field, the so-called Supergalactic Plane (SGP). This structure is studied here in three dimensions using both the new Optical Redshift Survey (ORS)…
In this work we want to study the average mass density profile of tens to hundreds of clusters of galaxies acting as lenses that produce a magnification bias on the SMGs, and to estimate their associated masses and concentrations for…
We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for…
We have measured the clustering properties of low-redshift (z < 0.3) sub-mm galaxies detected at 250 micron in the Herschel-ATLAS Science Demonstration Phase (SDP) field. We selected a sample for which we have high-quality spectroscopic…
We present five newly found galaxy clusters at z>0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have sufficient spectroscopically confirmed member…
Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun. They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %) and a small fraction of stars, dust, and cold gas, mostly locked in galaxies. In most…
We present results of a blind 21cm HI-line imaging survey of a galaxy overdensity located behind the Milky Way at $\ell,b$ $\approx$ 160 deg, 0.5 deg. The overdensity corresponds to a Zone-of-Avoidance crossing of the Perseus-Pisces…
We report the first weak-lensing detection of a large-scale filament funneling matter onto the core of the massive galaxy cluster MACSJ0717.5+3745. Our analysis is based on a mosaic of 18 multi-passband images obtained with ACS aboard the…
We present the first application of a spherical collapse model to a supercluster of galaxies. Positions and redshifts of $\sim 3000$ galaxies in the Shapley Supercluster (SSC) are used to define velocity caustics that limit the…
We describe the first optical survey of absorption systems associated with galaxy clusters at z= 0.3-0.9. We have cross-correlated SDSS DR3 quasars with high-redshift cluster/group candidates from the Red-Sequence Cluster Survey. We have…
In a large scale view of the universe, galaxies are the basic unit of structure. A typical bright galaxy may contain 100 billion stars and span tens of thousands of light years, but the empty expanses between the galaxies are much larger…
We report the discovery of 47 low surface brightness objects in deep images of a 3 x 3 degree field centered on the Coma cluster, obtained with the Dragonfly Telephoto Array. The objects have central surface brightness mu(g,0) ranging from…
We present a study of the shape, size, and spatial orientation of superclusters of galaxies. Approximating superclusters by triaxial ellipsoids we show that superclusters are flattened, triaxial objects. We find that there are no spherical…
The results of the study of the large-scale distribution of galaxies up to z ~0.8 in the field HS 47.5-22 on the basis of photometric data of the 1-meter Schmidt telescope of the BAO NAS Armenia are presented. The full sample contains…
We study the populations of stellar clumps in three high-redshift galaxies, at z=4.92, 4.88 and 4.03, gravitationally lensed by the foreground galaxy clusters MS1358, RCS0224 and MACS0940, respectively. The lensed galaxies consist of…
In the hierarchical theory of galaxy formation, a galaxy overdensity is a hallmark of a massive cosmic structure. However, it is less well understood how different types of galaxies trace the underlying large-scale structure. Motivated by…
We present a new, objectively selected, sample of galaxy overdensities detected in the Hubble Space Telescope Medium Deep Survey. These clusters/groups were found using an automated procedure which involved searching for statistically…
Using data from the Sloan Digital Sky Survey (SDSS; data release 7), we have conducted a search for local analogs to the extremely compact, massive, quiescent galaxies that have been identified at z > 2. We show that incompleteness is a…
A recently discovered quadruply-imaged QSO, SDSS J1004+4112 (Inada et al. 2003; Oguri et al. 2004) in the core of a $z=0.68$ galaxy cluster has an unprecedented image separation of ~13''. This lens gives us a unique opportunity to study the…
The first systematic study of the serendipitous X-ray source density around 10 high z (0.24<z<1.2) clusters performed with Chandra is presented. A factor \~2 overdensity has been found in 4 cluster fields. The result is statistically highly…