Investigation of properties of galaxy clusters in the Hercules supercluster region

We investigated the properties of galaxy clusters in the region of the Hercules supercluster using observational data from the SDSS and 2MASS catalogs and the NED. We have selected 13 galaxy clusters with a total dynamical mass of 4.82 × 10¹⁵ M _⊙ in a 100 × 45 Mpc supercluster region in the plane of the sky (0.030 < z < 0.041). In addition, our sample includes eight clusters from the immediate neighborhoods of the superclusters and ten field clusters at the same z. The derived properties of the rich Hercules supercluster are shown in comparison with the data for the poor Leo supercluster. The main parameters of the virialized galaxy cluster regions in the near infrared (K _s ) for the Hercules supercluster differ from those for the Leo supercluster: the number of galaxies and the total luminosity (to a limiting magnitude of ?21 _· ^m 5) increase with cluster mass (L _K,200 ∝ M ₂₀₀ ^0.91±0.07 and N ₂₀₀ ∝ M ₂₀₀ ^0.94±0.07 ), but the dependences are steeper by 0.28 and 0.22. In the virialized cluster regions, the fraction of early-type galaxies selected by the bulge contribution, concentration index, and u t= r color is, on average, 66% (60% in Leo, 70% in the field) among the galaxies brighter than ?23 _· ^m 3 and 54% (51% in Leo, 61% in the field) among the galaxies brighter than ?22 _· ^m 3. The fraction of early-type galaxies in the superclusters does not change with galaxy cluster mass and luminosity. The composite luminosity function of the rich Hercules supercluster is described by a Schechter function and does not differ from the luminosity function of the poor Leo supercluster for the luminosity interval [?26 ^m , ?21 _· ^m 5] but differs from the field luminosity function at the same z determined from ten galaxy clusters.     

Analysis of a sample of RC catalog objects in the region overlapping with the areas covered by FIRST and SDSS surveys. II: Optical identification with the SDSS survey and USNO-B1 and 2MASS catalogs

We report the results of optical identification of a sample of RC catalog radio sources with the FIRST and SDSS surveys. For 320 sources identified with NVSS and FIRST objects we perform optical identification with the SDSS survey. When selecting optical candidates we make maximum use of the information about the structure of radio sources as provided by the FIRST survey images. We find optical candidates for about 70% of all radio sources.     

Analysis of the properties of clusters of galaxies in the region of the Ursa Major supercluster

We analyze the properties of the clusters of galaxies in the region of the Ursa Major (UMa) supercluster using observational data from SDSS and 2MASS catalogs. The region studied includes a supercluster (with a galaxy and cluster overdensity of 3 and 15, respectively) and field clusters inside the 150-Mpc diameter surrounding region. The total dynamical mass of 10 clusters of galaxies in UMa is equal to 2.25 × 10¹⁵ M _⊙, and the mass of 11 clusters of galaxies in the UMa neighborhood is equal to 1.70 × 10¹⁵ M _⊙. The fraction of early-type galaxies brighter than M _K ^* + 1 in the virialized regions of clusters is, on the average, equal to 70%, and it is virtually independent on the mass of the cluster. The fraction of these galaxies and their average photometric parameters are almost the same both for UMa clusters and for the clusters located in its surroundings. Parameters of the clusters of galaxies, such as infrared luminosities up to a fixed magnitude, the mass-to-luminosity ratio, and the number of galaxies have almost the same correlations with the cluster mass as in other samples of galaxies clusters. However, the scatter of these parameters for UMa member clusters is twice smaller than the corresponding scatter for field clusters, possibly, due to the common origin of UMa clusters and synchronized dynamical evolution of clusters in the supercluster.     

Structure of clusters with bimodal distribution of galaxy line-of-sight velocities III: A1831

We study the A1831 cluster within the framework of our program of the investigation of galaxy clusters with bimodal velocity distributions (i.e., clusters where the velocities of subsystems differ by more than Δ _cz ∼ 3000 km/s).We identify two subsystems in this cluster: A1831A (cz = 18970 km/s) and A1831B (cz = 22629 km/s) and directly estimate the distances to these subsystems using three methods applied to early-type galaxies: the Kormendy relation, the photometric plane, and the fundamental plane. To this end, we use the results of our observations made with the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the data adopted from the SDSS DR6 catalog. We confirmed at a 99% confidence level that (1) the two subsystems are located at different distances, which are close to their Hubble distances, and (2) the two subsystems are located behind one another along the line of sight and are not gravitationally bound to each other. Both clusters have a complex internal structure, which makes it difficult to determine their dynamical parameters. Our estimates for the velocity dispersions and masses of the two clusters: 480 km/s and 1.9 × 10¹⁴ M _⊙ for A1831A, 952 km/s and 1.4 × 10¹⁵ M _⊙ for A1831B should be views as upper limits. At least three spatially and kinematically distinct groups of galaxies can be identified in the foreground cluster A1831A, and this fact is indicative of its incomplete dynamical relaxation. Neither can we rule out the possibility of a random projection. The estimate of the mass of the main cluster A1831B based on the dispersion of the line-of-sight velocities of galaxies is two-to-three times greater than the independent mass estimates based on the total K-band luminosity, temperature, and luminosity of the X-ray gas of the cluster. This fact, combined with the peculiarities of its kinematical structure, leads us to conclude that the cluster is in a dynamically active state: galaxies and groups of galaxies with large line-of-sight velocities relative to the center of the cluster accrete onto the virialized nucleus of the cluster (possibly, along the filament directed close to the line of sight).     

Investigation of the new Local Group galaxy VV 124

We present the results of our stellar photometry and spectroscopy for the new Local Group galaxy VV124 (UGC4879) obtainedwith the 6-m BTAtelescope. The presence of a fewbright supergiants in the galaxy indicates that the current star formation process is weak. The apparent distribution of stars with different ages in VV 124 does not differ from the analogous distributions of stars in irregular galaxies, but the ratio of the numbers of young and old stars indicates that VV 124 belongs to the rare Irr/Sph type of galaxies. The old stars (red giants) form the most extended structure, a thick disk with an exponential decrease in the star number density to the edge. Definitely, the young population unresolvable in images makes a great contribution to the background emission from the central galactic regions. The presence of young stars is also confirmed by the [OIII] emission line visible in the spectra that belongs to extensive diffuse galactic regions. The mean radial velocity of several components (two bright supergiants, the unresolvable stellar population, and the diffuse gas) is υ _h = −70 ± 15 km s⁻¹ and the velocity with which VV 124 falls into the Local Group is υ _LG = −12 ± 15 km s⁻¹. We confirm the distance to the galaxy (D = 1.1 ± 0.1 Mpc) and the metallicity of red giants ([Fe/H] = −1.37) found by Kopylov et al. (2008). VV 124 is located on the periphery of the Local Group approximately at the same distance from M31 and our Galaxy and is isolated from other galaxies. The galaxy LeoA nearest to it is 0.5 Mpc away.     

Bacteria and Viruses in Arctic Sea Ice

Oceanology - We studied vertical distribution of bacteria and viruses in different layers of the Arctic sea ice drilled at the North Pole. The sampled multi-year ice was characterized by uneven...     

The structure of clusters with bimodal distributions of galaxy radial velocities,I. A1035

The structure of the A1035 cluster of galaxies (10^h32^m + 40°13′, cz ～ 22000 kms^?1), which exhibits a bimodal distribution of galaxy radial velocities (ΔV ≈ 3000 kms^?1), is analyzed using three methods of determining the relative distances to clusters from early-type galaxies: the Kormendy relation corrected for the dependence of residuals on galaxy magnitude, the photometric plane, and the fundamental plane. We use the data obtained with the l-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and SDSS (DR5) data to show that A1035 consists of two gravitationally unbound independent clusters. These clusters with the velocity dispersions of 566 km s^?1 and 610 km s^?1 and masses within R ₂₀₀ equal to 2.7 · 10¹⁴ and 3.5 · 10¹⁴ M _⊙, respectively, obey the Hubble law.     

Detailed study of the Ursa Major supercluster of galaxies using the 2MASS and SDSS Catalogs

We study the infrared (K _s band) properties of clusters of galaxies in the Ursa Major supercluster using data from 2MASS (Two-Micron All-Sky Survey) and SDSS (Sloan Digital Sky Survey). We identified three large filaments with mean redshifts of z = 0.051, 0.060, and 0.071. All clusters of the supercluster are located in these filaments. We determined the total K _s-band luminosities and masses for 11 clusters of galaxies within comparable physical regions (within a radius R ₂₀₀ close to the virial radius) using a homogeneous method. We constructed a combined luminosity function for the supercluster in this region, which can be described by the Schechter function with the following parameters: M _K ^* = ?24.50 and α = ?0.98. The infrared luminosities of the clusters of galaxies correlate with their masses; the M/L _K ratios of the systems increase with their masses (luminosities), with most of the Ursa Major clusters of galaxies (particularly the richer ones) closely following the relations derived previously for a large sample of clusters and groups of galaxies. The total mass-to-infrared-luminosity ratio is 52 M _⊙/L _⊙ for six Abell clusters and 49M _⊙/L _⊙ for all of the clusters, except Anon2.     

Analysis of the RC catalog sample in the region overlapping with the regions of the FIRST and SDSS surveys: I. Identification of sources with the VLSS, TXS, NVSS, FIRST, and GB6 catalogs

Radio sources of the RC catalog produced in 1980–1985 at RATAN-600 radio telescope based on a deep survey of a sky strip centered on the declination of the SS433 source are optically identified in the region overlapping with FIRST and SDSS surveys (about 132?° large). The NVSS catalog was used as the reference catalog for refining the coordinates of the radio sources. The morphology is found for about 75% of the objects of the sample and the ratio of single, double and multicomponent radio sources is computed based on FIRST radio maps. The 74, 365, 1400, and 4850MHz data of the VLSS, TXS, NVSS, FIRST, and GB6 catalogs are used to analyze the shape of the spectra.