We examine resolved spectroscopic data obtained with the Keck II telescope for 44 spheroidal galaxies in the fields of two rich clusters, Cl 0024+16 (z=0.40) and MS 0451-03 (z=0.54) and contrast this with similar data for 23 galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field. For each galaxy we examine the case for systemic rotation, derive central stellar velocity dispersions sigma and photometric ellipticities epsilon. Using morphological classifications obtained via Hubble Space Telescope imaging as the basis, we explore the utility of our kinematic quantities in distinguishing between pressure-supported ellipticals and rotationally supported lenticulars (S0s).
A detailed kinematic analysis of ionized gas in the nearby irregular galaxy NGC 4449 is presented. Observations were conducted in the spectral lines of H{alpha} and [S II]. Our scanning Fabry-Perot interferometric observations are presented from both a global and a local perspective. We have analyzed the global velocity field, the spatially extended diffuse gaseous component, and the H II region populations and, furthermore, have determined the rotation curve based on the heliocentric radial velocities of the global H{alpha} spatial distribution.
Measurements of 544 radial velocities, 229 optical and 315 in the 21cm HI line, are presented for galaxies, mostly in the declination strip +33.5 deg<Dec<+39.5deg in the region of the Pisces-Perseus supercluster. These are combined with other available data to investigate the linear structure identified as the main supercluster ridge. The main ridge of the supercluster extends at least 50h^-1Mpc before it disappears into the zone of avoidance east of Perseus. Confinement both on the plane of the sky and in the velocity dimension imply an axial ratio of greater than ten to one and an inclination with respect to the plane of the sky of less than about 12 degrees. The smoothed volume density contrast over the whole ridge averages more than a factor of 6 relative to the average density derived for the whole sample. The relative proximity, low inclination to the plane of the sky, and high contrast relative to the foreground and background, help to make the Pisces-Perseus filament one of the most prominent features in the extragalactic sky on large scales.
We search for the effects of metallicity on B and Be stars in the Small and Large Magellanic Clouds (SMC and LMC) and in the Milky Way (MW), by extending our previous analysis of B and Be star populations in the LMC to the SMC. The rotational velocities of massive stars and the evolutionary status of Be stars are examined with respect to their environments. Spectroscopic observations of hot stars belonging to the young cluster SMC-NGC 330 and its surrounding region were obtained with the VLT-GIRAFFE facilities in MEDUSA mode. We determined fundamental parameters for B and Be stars with the GIRFIT code, taking the effect of fast rotation and the age of observed clusters into account. We compared the mean vsini obtained by spectral type- and mass-selection for field and cluster B and Be stars in the SMC with the one in the LMC and MW.
The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated. We aim to obtain new insights into the internal dynamics of the cluster Abell 2345. This cluster exhibits two non-symmetric radio relics well studied through recent, deep radio data. Our analysis is based on redshift data for 125 galaxies acquired at the Telescopio Nazionale Galileo and on new photometric data acquired at the Isaac Newton Telescope. We also use ROSAT/HRI archival X-ray data. We combine galaxy velocities and positions to select 98 cluster galaxies and analyze the internal dynamics of the cluster.
We examine a possible supergroup in the direction of the Eridanus constellation using 6dF Galaxy Survey second data release (6dFGS DR2) positions and velocities together with Two-Micron All-Sky Survey and Hyper-Lyon-Meudon Extragalactic DAtabase photometry. We perform a friends-of-friends analysis to determine which galaxies are associated with each substructure before examining the properties of the constituent galaxies.
The present investigation was undertaken to get more information about the structure and the rotation of our Galaxy in the Puppis OB association area, towards longitude l"=244{deg}. We give here new spectrophotometric and kinematic results which were obtained through the measurements of plates taken at the ESO Objective Prism Astrograph.
We present a combined X-ray and optical analysis of three bimodal galaxy clusters selected as merging candidates at z~0.1. These targets are part of MUSIC (MUlti-Wavelength Sample of Interacting Clusters), which is a general project designed to study the physics of merging clusters by means of multi-wavelength observations.
We study the dynamical status of the galaxy system ZwCl 2341.1+0000, a filamentary multi-Mpc galaxy structure associated with a complex diffuse radio emission. Our analysis is mainly based on new spectroscopic data for 128 galaxies acquired at the Italian Telescopio Nazionale Galileo. We also use optical data available in the Sloan Digital Sky Survey and X-ray data from the Chandra archive. We select 101 cluster member galaxies and compute the cluster redshift <z>~0.2693 and the global line-of-sight velocity dispersion {sigma}_V_~1000km/s. Our optical analysis agrees with the presence of at least three, likely four or more, optical subclusters causing the south-south-east-north-north-west (SSE-NNW) elongation of the galaxy distribution and a significant velocity gradient in the south-north direction. In particular, we detect an important low-velocity subclump in the southern region, roughly coincident with the brightest peak of the diffuse radio emission but with a clear offset between the optical and radio peaks. We also detect one (or two) optical subcluster(s) at north, in correspondence with the second brightest radio emission, and another one in the central cluster region, where a third diffuse radio source has been recently detected. A more refined analysis involving the study of the 2D galaxy distribution suggests an even more complex structure. Depending on the adopted model, we obtain a mass estimate M_sys_~1-3x10^15^h_70_^-1^M_{sun} for the whole system. As for the X-ray analysis, we confirm the SSE-NNW elongation of the intracluster medium and detect four significant peaks. The X-ray emission is strongly asymmetric and offsetted with respect to the galaxy distribution, thus suggesting a merger caught in the phase of post-core-core passage. Our findings support two possible hypotheses for the nature of the diffuse radio emission of ZwCl 2341.1+0000: a two relics + halo scenario or diffuse emission associated with the infall and merging of several galaxy groups during the first phase of the cluster formation.