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|Radio and Far-Infrared Emission as Tracers of Star Formation and Active Galactic Nuclei in Nearby Cluster Galaxies|
We have studied the radio and far-infrared (FIR) emission from 114galaxies in the seven nearest clusters (<100 Mpc) with prominentX-ray emission to investigate the impact of the cluster environment onthe star formation and active galactic nucleus (AGN) activity in themember galaxies. The X-ray selection criterion is adopted to focus onthe most massive and dynamically relaxed clusters. A large majority ofcluster galaxies show an excess in radio emission over that predictedfrom the radio-FIR correlation, the fraction of sources with radioexcess increases toward cluster cores, and the radial gradient in theFIR/radio flux ratio is a result of radio enhancement. Of theradio-excess sources, 70% are early-type galaxies, and the same fractionhost an AGN. The galaxy density drops by a factor of 10 from thecomposite cluster center out to 1.5 Mpc, yet galaxies show no change inFIR properties over this region and show no indication of masssegregation. We have examined in detail the physical mechanisms thatmight impact the FIR and radio emission of cluster galaxies. Whilecollisional heating of dust may be important for galaxies in clustercenters, it appears to have a negligible effect on the observed FIRemission for our sample galaxies. The correlations between radio and FIRluminosity and radius could be explained by magnetic compression fromthermal intracluster medium pressure. We also find that simple delayedharassment cannot fully account for the observed radio, FIR, and mid-IRproperties of cluster galaxies.
|FLASH redshift survey - I. Observations and catalogue|
The FLAIR Shapley-Hydra (FLASH) redshift survey catalogue consists of4613 galaxies brighter than bJ= 16.7 (corrected for Galacticextinction) over a 700-deg2 region of sky in the generaldirection of the Local Group motion. The survey region is a70°× 10° strip spanning the sky from the ShapleySupercluster to the Hydra cluster, and contains 3141 galaxies withmeasured redshifts. Designed to explore the effect of the galaxyconcentrations in this direction (in particular the Supergalactic planeand the Shapley Supercluster) upon the Local Group motion, the 68 percent completeness allows us to sample the large-scale structure betterthan similar sparsely-sampled surveys. The survey region does notoverlap with the areas covered by ongoing wide-angle (Sloan or 2dF)complete redshift surveys. In this paper, the first in a series, wedescribe the observation and data reduction procedures, the analysis forthe redshift errors and survey completeness, and present the surveydata.
|Galaxy Luminosity Functions from Deep Spectroscopic Samples of Rich Clusters|
Using a new spectroscopic sample and methods accounting forspectroscopic sampling fractions that vary in magnitude and surfacebrightness, we present R-band galaxy luminosity functions (GLFs) for sixnearby galaxy clusters with redshifts of 4000 kms-1
|Nearby Optical Galaxies: Selection of the Sample and Identification of Groups|
In this paper we describe the Nearby Optical Galaxy (NOG) sample, whichis a complete, distance-limited (cz<=6000 km s-1) andmagnitude-limited (B<=14) sample of ~7000 optical galaxies. Thesample covers 2/3 (8.27 sr) of the sky (|b|>20deg) andappears to have a good completeness in redshift (97%). We select thesample on the basis of homogenized corrected total blue magnitudes inorder to minimize systematic effects in galaxy sampling. We identify thegroups in this sample by means of both the hierarchical and thepercolation ``friends-of-friends'' methods. The resulting catalogs ofloose groups appear to be similar and are among the largest catalogs ofgroups currently available. Most of the NOG galaxies (~60%) are found tobe members of galaxy pairs (~580 pairs for a total of ~15% of objects)or groups with at least three members (~500 groups for a total of ~45%of objects). About 40% of galaxies are left ungrouped (field galaxies).We illustrate the main features of the NOG galaxy distribution. Comparedto previous optical and IRAS galaxy samples, the NOG provides a densersampling of the galaxy distribution in the nearby universe. Given itslarge sky coverage, the identification of groups, and its high-densitysampling, the NOG is suited to the analysis of the galaxy density fieldof the nearby universe, especially on small scales.
|Hα objective prism survey of Abell 1060|
As part of a continuing study of the effect of cluster environment onthe star formation properties of galaxies, we have undertaken anHα objective prism survey of the nearby cluster, Abell 1060. Wedetect 33 galaxies in emission, 24 of which are cluster members. Wepresent new radial velocity measurements and Hα + [N Ii]equivalent widths and fluxes for a number of these galaxies. Wedistinguish between galaxies with diffuse and compact emission, thelatter having been associated in previous work with a disturbedmorphology of the galaxy and most likely resulting from tidally-inducedstar formation from galaxy-galaxy or cluster-galaxy interactions. Thefraction of cluster spirals in Abell 1060 detected with compact emissionagrees with the expected fraction for a cluster of its richness, asderived from results of a previous survey of 8 clusters. Some of thedetected cluster early-type spirals exhibit anomalously high globalHα equivalent widths, as compared to galaxies of similar type inthe field.
|The Catalog of Southern Ringed Galaxies|
The Catalog of Southern Ringed Galaxies (CSRG) is a comprehensivecompilation of diameters, axis ratios, relative bar position angles, andmorphologies of inner and outer rings, pseudorings, and lenses in 3692galaxies south of declination -17 deg. The purpose of the catalog is toevaluate the idea that these ring phenomena are related to orbitalresonances with a bar or oval in galaxy potentials. The catalog is basedon visual inspection of most of the 606 fields of the Science ResearchCouncil (SRC) IIIa-J southern sky survey, with the ESO-B, ESO-R, andPalomar Sky surveys used as auxiliaries when needed for overexposed coreregions. The catalog is most complete for SRC fields 1-303 (mostly southof declination -42 deg). In addition to ringed galaxies, a list of 859mostly nonringed galaxies intended for comparison with other catalogs isprovided. Other findings from the CSRG that are not based on statisticsare the identification of intrinsic bar/ring misalignment; bars whichunderfill inner rings; dimpling of R'1pseudorings; pointy, rectangular, or hexagonal inner or outer ringshapes; a peculiar polar-ring-related system; and other extreme examplesof spiral structure and ring morphology.
|Surface photometry of the Hydra I cluster of galaxies. I - Photometric data|
Surface photometry was made for 137 galaxies on a UK Schmidt plate whosecenter is located at the center of the Hydra I (A1060 ) cluster ofgalaxies. For 133 of the 137 galaxies, such photometric parameters astotal magnitude, equivalent radius, concentration indices, and meansurface brightness were obtained. The total magnitudes were comparedwith those in the literature to check the accuracy of the present data.The estimated accuracy in the total magnitudes is about 0.1 mag at mostfor majority of the galaxies.
|General study of group membership. II - Determination of nearby groups|
We present a whole sky catalog of nearby groups of galaxies taken fromthe Lyon-Meudon Extragalactic Database. From the 78,000 objects in thedatabase, we extracted a sample of 6392 galaxies, complete up to thelimiting apparent magnitude B0 = 14.0. Moreover, in order to considersolely the galaxies of the local universe, all the selected galaxieshave a known recession velocity smaller than 5500 km/s. Two methods wereused in group construction: a Huchra-Geller (1982) derived percolationmethod and a Tully (1980) derived hierarchical method. Each method gaveus one catalog. These were then compared and synthesized to obtain asingle catalog containing the most reliable groups. There are 485 groupsof a least three members in the final catalog.
|Optical identifications of IRAS point sources - The Fornax, Hydra I and Coma clusters|
Optical identifications are presented for 66 IRAS point sources in theregion of the Fornax cluster of galaxies, 106 IRAS point sources in theregion of the Hydra I cluster of galaxies (Abell 1060), and 59 IRASpoint sources in the region of the Coma cluster of galaxies (Abell1656). Eight other sources in Hydra I do not have optical counterpartsand are very probably due to IR cirrus. Twenty-three (35 percent) of theFornax sources are associated with stars and 43 (65 percent) withgalaxies; 48 (42 percent) of the Hydra I sources are associated withstars and 58 (51 percent) with galaxies; 18 (31 percent) of the Comasources are associated with stars and 41 (69 percent) with galaxies. Thestellar and infrared cirrus surface density is consistent with thegalactic latitude of each field.
|The Hydra I cluster of galaxies. V - A catalogue of galaxies in the cluster area|
The available information for 581 galaxies in the area of the Hydra I (= Abell 1060) cluster is compiled into a catalog. Positions, magnitudes,diameters, position angles, radial velocities, and morphological typesare given. A first determination of the luminosity function of Hydra Iis attempted. An assessment of the photometric errors in the isophotalmagnitudes is included.
|Southern Galaxy Catalogue.|
|The Hydra I cluster of galaxies. II - First results from H I observations|
The number of known redshifts in the area of the Hydra I cluster hasbeen raised to 96, through the detection of 17 galaxies in the course ofH I 21-cm line observations of 42 galaxies in this field. Evidence isalso found for an increase of the H I deficiency factor radially inwardsto the center of the cluster. The cluster's distance modulus, relativeto the Virgo cluster from the blue magnitude Tully-Fisher relation is inagreement with other determinations and with the value that is based onthe ratio of cluster redshifts; a constraint to the infall velocity ofthe Local Group toward the Virgo cluster is therefore given to values ofless than 350 km/sec.
|The Hydra I cluster of galaxies - A unique case of membership definition|
New optical radial velocities for 71 galaxies in the Hydra I cluster arepresented. The recession velocity of the cluster is determined to 3425km/sec, yielding a distance of about 45.7 Mpc. The overall velocitydispersion is 676 km/sec. Results of galaxy counts could be fitted by atwo-component model. Many of the global cluster properties of Hydra Ilike, e.g., total galaxy content, velocity dispersion, X-ray flux, etc.,suggest a remarkable similarity with the Virgo cluster. No foregroundgalaxies and no background galaxies were noted in the observed area upto about 8000 km/sec, suggesting regions of empty space of the order of40-50 Mpc extent along the line of sight.
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