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|Nature and environment of Very Luminous Galaxies|
The most luminous galaxies in the blue passband have a largercorrelation amplitude than L* galaxies. They do not appear tobe preferentially located in rich clusters or groups, but a significantfraction of them seem to be in systems which include fainter members. Wepresent an analysis of fields centered on 18 Very Luminous Galaxies(MB <=-21) selected from the Southern Sky Redshift Survey2, based on new observations and public data of the 2dF Galaxy RedshiftSurvey; we present also additional data on a CfA VLG and on Arp 127. Wefind that all the selected VLGs are physically associated with faintercompanions. Moreover, there is a relation between the VLG morphology(early or late) and the dynamical properties of the system, whichreflects the morphology-density relation. 6 out of the 18 SSRS2 VLGs areearly type galaxies: 2 are in the center of rich Abell clusters withvelocity dispersion sigma ~ 600 km s-1, and the other 4are in poor clusters or groups with sigma ~ 300. The VLG extractedfrom the CfA catalog is also an elliptical in a Zwicky cluster. Theremaining 2/3 of the sample are late-type VLGs, generally found inpoorer systems with a larger spread in velocity dispersion, from ~ 100up to ~ 750 km s-1. The low velocity dispersion, late-typeVLG dominated systems appear to be analogous to our own Local Group. Thepossibile association of VLG systems with dark matter halos with masscomparable to rich groups or clusters, as suggested by the comparablecorrelation amplitude, would imply significant differences in the galaxyformation process. This work also shows that observing fields aroundVLGs represents an effective way of identifying galaxy systems which arenot selected through other traditional techniques.Figures 1, 2 and Appendix B are only available in electronic form athttp://www.edpsciences.org
|Accurate Positions for MCG Galaxies|
We have measured accurate celestial coordinates for 4741 extragalacticobjects, primarily drawn from a list of MCG galaxies with no recentlypublished accurate positions. The standard deviations in the newpositions depend slightly on the measurement method but are on the orderof 1.0" to 1.2". Standard deviations in the original MCG positions areconfirmed to be at the 1.5′-2.0′ level. These new positionswere integrated into NED in 1997 December.
|The Southern Sky Redshift Survey|
We report redshifts, magnitudes, and morphological classifications for5369 galaxies with m_B <= 15.5 and for 57 galaxies fainter than thislimit, in two regions covering a total of 1.70 sr in the southerncelestial hemisphere. The galaxy catalog is drawn primarily from thelist of nonstellar objects identified in the Hubble Space TelescopeGuide Star Catalog (GSC). The galaxies have positions accurate to ~1"and magnitudes with an rms scatter of ~0.3 mag. We compute magnitudes(m_SSRS2) from the relation between instrumental GSC magnitudes and thephotometry by Lauberts & Valentijn. From a comparison with CCDphotometry, we find that our system is homogeneous across the sky andcorresponds to magnitudes measured at the isophotal level ~26 magarcsec^-2. The precision of the radial velocities is ~40 km s^-1, andthe redshift survey is more than 99% complete to the m_SSRS2 = 15.5 maglimit. This sample is in the direction opposite that of the CfA2; incombination the two surveys provide an important database for studies ofthe properties of galaxies and their large-scale distribution in thenearby universe. Based on observations obtained at Cerro TololoInter-American Observatory, National Optical Astronomy Observatories,operated by the Association of Universities for Research in Astronomy,Inc., under cooperative agreement with the National Science Foundation;Complejo Astronomico El Leoncito, operated under agreement between theConsejo Nacional de Investigaciones Científicas de laRepública Argentina and the National Universities of La Plata,Córdoba, and San Juan; the European Southern Observatory, LaSilla, Chile, partially under the bilateral ESO-ObservatórioNacional agreement; Fred Lawrence Whipple Observatory;Laboratório Nacional de Astrofísica, Brazil; and the SouthAfrican Astronomical Observatory.
|Properties of Very Luminous Galaxies|
Recent analysis of the data from the Southern Sky Redshift Surveyextension (SSRS2) based on cell counts and the two-point correlationfunction has shown that very luminous galaxies are much more stronglyclustered than fainter galaxies. In fact, the amplitude of thecorrelation function of very luminous galaxies (L > L^*)asymptotically approaches that of R >= 0 clusters. In this paper weinvestigate the properties of the most luminous galaxies, with blueabsolute magnitudes M_B <= -21. We find that (1) the population mixis comparable to that in other ranges of absolute magnitude; (2) only asmall fraction are located in bona fide clusters; (3) the brightgalaxy-cluster cross-correlation function is significantly higher onlarge scales than that measured for fainter galaxies; (4) thecorrelation length of galaxies brighter than M_B ~ -20.0, expressed as afunction of the mean interparticle distance, appears to follow theuniversal dimensionless correlation function found for clusters andradio galaxies; (5) a large fraction of the bright galaxies are ininteracting pairs, while others show evidence for tidal distortions andsome appear to be surrounded by faint satellite galaxies. We concludethat very luminous optical galaxies differ from the normal population ofgalaxies in both clustering and other respects. We speculate that thispopulation is a highly biased tracer of mass, being associated with darkhalos with masses more comparable to clusters than to typical loosegroups.
|An 18-cm OH and 21-cm H I survey of luminous far-infrared galaxies. II - H I properties|
As a part of the present 18-cm OH and 21-cm H I survey of luminousfar-infrared galaxies, the paper provides H I data obtained at Nancayfor 88 IRAS galaxies, with FIR luminosity above 10 to the 10th solarluminosity. Among them, 64 are measured here for the first time. Whenrestricting to radial velocities smaller than 11,000 km/s, the detectionrate is equal to 85 percent, independent of the distance. These galaxiesappear as giant ones in dimension, total mass and total blue luminosity.All these parameters increase with increasing FIR luminosity. ExtremeFIR luminosity is thus related to gigantism, which could be the resultof mergers. These galaxies are also deficient in their relative H Icontent, in the sense that their global relative H I content issignificantly smaller than in classical galaxies of the Hubble sequence.
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