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Публикации по объекту
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.
| 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.
| Two Galaxy Clusters: A3565 and A3560
We report 102 new redshifts and magnitudes for a sample of galaxies toR_F~15.5 mag in a 2.17dx2.17d region centered on the galaxy IC 4296, themost luminous member of the A3565 Cluster. Up to the limiting magnitude,we find 29 cluster members and measure a velocity dispersion ofsigma=228 km s^-1. The estimated total mass for this system is~3.0x10^13 h^-1 M_solar [where h=H_0/(100 km s^-1 Mpc^-1)], and itsdynamical properties are quite typical of poor clusters presenting X-rayemission. We also find that galaxies with absorption lines are moreconcentrated toward the center of the cluster, while systems withemission lines are mainly located in the outer parts. The small velocitydispersion of the cluster, coupled with the known presence of aninteracting pair of galaxies, and the large extent of the brightestcluster galaxy, could indicate that galaxy formation through mergers maystill be underway in this system. The surveyed region also containsgalaxies belonging to the Shapley concentration cluster A3560. Within30' of the cluster center, we detect 32 galaxies, for which we measure avelocity dispersion of 588 km s^-1 and a mass of ~2x10^14 h^-1 M_solar.However, because our sample is restricted to galaxies brighter than M^*,these values should be considered only as rough estimates.
| The environment of HII galaxies
Recent morphological studies by Telles & Terlevich of HII galaxies,i.e. dwarf galaxies dominated by a very luminous starburst, haveindicated that luminous HII galaxies tend to show disturbed morphologysuggestive of tidal interactions triggering the present starburst, whilelow-luminosity HII galaxies tend, instead, to be symmetric and regular.To check the tidal origin of the starburst in HII galaxies, we havesearched for companions in the neighbourhood of a sample of 51 HIIgalaxies. We found that only 12 HII galaxies have a neighbour within aprojected distance of 1Mpc and 250 km s^-1 in velocity difference and,of these 12, only four have a luminous (M_B<-19)neighbour. Surprisingly, isolated HII galaxies tend to be of highluminosity and disturbed morphology, while HII galaxies with neighbourstend to be low-luminosity regular HII galaxies. Furthermore, the metalabundance and the equivalent width of the emission lines in HII galaxiesdo not depend on the presence of a companion. These results are opposedto what is expected if interaction with a bright companion is the mainmechanism triggering the starbursts. We have also found a loose group ofHII galaxies with no luminous companion. For this, there is theadditional difficulty of understanding how these starbursts aresynchronized on time-scales of less than 10^7 yr in systems separated by~1-2 Mpc.
| 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.
| The common halo and tidal features of the interacting pair of galaxies NGC 5215a and B revealed by the co-addition of eight Schmidt plates
The interacting pair of galaxies NGC 5215a and b has been investigatedby means of a coadded data array of APM scans of eight Schmidt plates.The pair is found to be embedded in a common halo, and each member has atidal tail which trails the rotation of the core region. Distortions ofthe isophotes of the pair confirm the tidal interaction between the twogalaxies. A detached filament to the north of the pair is presumed toconsist of stars tidally stripped from the pair, and the halo isconsiderably extended to the south, presumably due to further starsbecoming unbound. The mass within the common halo is at least about 8 x10 to the 10th solar masses. The large spiral NGC 5220, at a similardistance, forms a much disturbed chain with the components of NGC 5215and some smaller galaxies.
| The plane W(Na I) X W(Mg I) - Effects of interstellar Na I in a sample of southern galaxies
Galaxy spectra from a subsample of the Southern Sky Redshift Survey databank were used to study the equivalent width plane for the lines Na Ilambda 5893 A vs Mg I lambda 5175 A. An estimate of how important thecontribution of the interstellar gas for the sodium line is compared tothat of the stellar population. The sample is made up of galaxies withmorphological types from E to Sc and are distributed up to radialvelocities of 25,000 km/s, most of them smaller than 15,000 km/s. Mostearly type galaxies with dust lanes, particularly nearly edge-on So's,present an enhancement of the Na I line. Inclined spiral galaxies tendto present enhanced Na I with respect to face-on spirals. This tendency,previously found in a smaller sample of galaxies limited to V equal toor less than 6000 km/s, is now confirmed for more distant ones. In thelarge velocity sample it shows the global bulge rather than the verynucleus; the persistence of the effect suggests that the scale height ofthe gas layer in the central disk can reach a considerable fraction ofthe bulge radius.
| A wide angle redshift survey of the Hydra-Centaurus region
Spectroscopic observations of 266 galaxies in the Hya-Cen region arereported. Redshift data obtained at 350-700 nm with dispersion 21 nm/mmusing the UNIT spectrograph and RPCS detector on the 1.9-m RadcliffeReflector telescope at SAO during March 1985, May 1986, and March 1987are presented in tables and graphs and briefly characterized. It isshown that the Hya supercluster is separated from the Cen superclusterby a large void at right ascension 11 h 40 min, declination -35 deg, andradial velocity 5200 km/sec; a bridge of galaxies at velocity about 3200km/sec connects the two superclusters.
| Redshift observations in the Centaurus-Hydra supercluster region. I
The paper presents 111 new redshifts in the region of theCentaurus-Hydra supercluster. Also presented is the growth of theHydra-Centaurus structures as a function of the percolation vector, thesurface distribution of galaxies in this region, and the distribution inredshift of the observed galaxies.
| Southern Galaxy Catalogue.
Not Available
| Atlas of interacting galaxies, Part. II and the concept of fragmentation of galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...28....1V&db_key=AST
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