J/ApJ/607/810ivo://CDS.VizieR/J/ApJ/607/810doi:10.26093/cds/vizier.16070810CDSMadore B.F.Freedman W.L.Bothun G.D.2018-05-16T06:56:22Z2018-03-01T06:59:42ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxy-clustersradial-velocityWe investigate the number of physical companion galaxies for a sample of relatively isolated elliptical galaxies. The NASA/IPAC Extragalactic Database (NED) has been used to reinvestigate the incidence of satellite galaxies for a sample of 34 elliptical galaxies, first investigated by Bothun & Sullivan (1977PASP...89....5B) using a visual inspection of Palomar Sky Survey prints out to a projected search radius of 75 kpc. We have repeated their original investigation using data cataloged in NED. Nine of these elliptical galaxies appear to be members of galaxy clusters; the remaining sample of 25 galaxies reveals an average of +1.0+/-0.5 apparent companions per galaxy within a projected search radius of 75 kpc, in excess of two equal-area comparison regions displaced by 150-300 kpc. This is significantly larger than the +0.12+/-0.42 companions/galaxy found by Bothun & Sullivan (1977PASP...89....5B) for the identical sample. Making use of published radial velocities, mostly available since the completion of the Bothun-Sullivan study, identifies the physical companions and gives a somewhat lower estimate of +0.4 companions per elliptical galaxy. This is still 3 times larger than the original statistical study, but given the incomplete and heterogeneous nature of the survey redshifts in NED, it still yields a firm lower limit on the number (and identity) of physical companions. An expansion of the search radius out to 300 kpc, again restricted to sampling only those objects with known redshifts in NED, gives another lower limit of 4.5 physical companions per galaxy. (Excluding five elliptical galaxies in the Fornax Cluster, this average drops to 3.5 companions per elliptical.) These physical companions are individually identified and listed, and the ensemble-averaged radial density distribution of these associated galaxies is presented. For the ensemble, the radial density distribution is found to have a falloff consistent with {rho}{prop.to}R^-0.5^ out to approximately 150 kpc. For non-Fornax Cluster companions the falloff continues out to the 300 kpc limit of the survey. The velocity dispersion of these companions is found to reach a maximum of 350 km/s at around 120 kpc, after which they fall at a rate consistent with Keplerian falloff. This falloff may then indicate the detection of a cut-off in the mass-density distribution in the elliptical galaxies' dark matter halo at ~100 kpc.2004ApJ...607..810Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/607/810CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/16 : Reference Catalogue of Bright GalaxiesVII/112 : RC2 Catalogue (de Vaucouleurs+ 1976)VII/155 : Third Reference Cat. of Bright Galaxies (RC3)J/A+AS/113/151 : Velocity dispersions for elliptical galaxiesJ/AJ/110/1032 : APM elliptical galaxies radial velocities (Muriel+ 1995)J/other/Sci/348.418 : Isolated compact elliptical galaxieshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/607/810https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/607/810http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/607/810https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/607/810https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/607/810http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/607/810GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/607/810/table2 (Companion-Galaxy Counts within R=75 kpc of Isolated Ellipticals)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/607/810/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/607/810/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/607/810/table2?GETtext/xml+votable180.050000true22.8364792-6.86806110.0055555555555555566/6087 6093 7385 7655 8193 8195 11263 11791 12018 17472 17605 17612 18269 24732 24733 25100 25383 25533 25768 26125 27079 27186 28142 34533 34542 36152 36153 36156 36785 38842 40252 44000 44995 48160https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/607/810?format=asciidefaultJ/ApJ/607/810/table3Velocity-confirmed Companions within R=300 kpcrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNGC[0584/6958] Central elliptical galaxy namemeta.id;meta.mainintn_NGC[n] Note on NGC (1)meta.notecharsigmaRadial-velocity dispersionkm/sinstr.dispersionintNameConfirmed galaxy companion namemeta.id.assoccharn_NameFlag on Name (2)meta.notecharRad? Projected radial separation from ellipticalarcminspect.dopplerVelocfloatnullableDRV? Differential radial velocity (3)km/sspect.dopplerVeloc;arith.diffintnullableJ/ApJ/607/810/table2Companion-Galaxy Counts within R=75 kpc of Isolated EllipticalsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNGC[0584/6958] Central elliptical galaxy namemeta.id;meta.mainintNcNumber of galaxy companion(s)meta.numberintnullableN75[0/134] Total counts in the 75 kpc circular areameta.numberintN[0/85] Field counts to the northmeta.numberintS[0/96] Field counts to the southmeta.numberintExcessStatistical excessstat.weight;phys.atmolfloate_ExcessUncertainty in Excessstat.error;phot.color.excessfloatBS77Number quoted on a galaxy-by-galaxy basis by BS77 (Bothun & Sullivan 1977PASP...89....5B)meta.numberfloatVgsr[1141/2960] Galactic standard of rest velocitykm/sphys.veloc;pos.galacticintS75[0/2] Number of radial velocity-confirmed companions inside 75 kpc search radiusmeta.numberintL150[0/28] Number of radial velocity-confirmed companions inside 150 kpc search radiusmeta.numberintSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main