J/ApJ/806/268ivo://CDS.VizieR/J/ApJ/806/268doi:10.26093/cds/vizier.18060268CDSIrwin J.A.Dupke R.Carrasco E.R.Maksym W.P.Johnson L.,White III R.E.2018-05-14T05:41:28Z2017-09-27T09:35:31ZCDS support team

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

cds-question@unistra.frgalaxy-clustersgravitational-lensingvisible-astronomysloan-photometryredshiftedThe Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ~1350 km/s. One group was most likely a low-mass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2-1.5x10^14^ M_{sun}_ fossil group with an M_r_=-24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or near-fossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups.2015ApJ...806..268Ihttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/806/268CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)J/AJ/137/3942 : Fossil galaxy groups (La Barbera+, 2009)J/ApJ/833/194 : Group of galaxies in gravitational lens fields (Wilson+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/806/268https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/806/268http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/806/268https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/806/268https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/806/268http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/806/268GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/806/268/table1 (Redshifts and Magnitudes of the Observed Galaxies)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/806/268/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/806/268/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/806/268/table1?GETtext/xml+votable180.050000true159.6328548.827430560.0055555555555555566/5927https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/806/268?format=asciiOpticaldefaultJ/ApJ/806/268/table1Redshifts and Magnitudes of the Observed GalaxiesSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGroup[ABC] Galaxy's group (1)meta.codecharIDSource Extractor galaxy identifier (2)meta.id;meta.maincharOtherOther IDmeta.idcharRAJ2000Hour of the Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainr'mag? Total magnitude in r'-bandmagphot.mag;em.opt.Rfloatnullablei'mag? Total magnitude in i'-bandmagphot.mag;em.opt.Ifloatnullabler'-i? Sloan r'-i color measured inside a fixed aperture of 1.2"magphot.color;em.opt.R;em.opt.IfloatnullablezRedshift, corrected to the heliocentric systemsrc.redshiftdoublee_zUncertainty in zstat.error;src.redshiftdoubleR? R value (Tonry & Davis 1979AJ.....84.1511T)stat.fit.paramfloatnullableNEm[2/8]? Number of emission lines used to calculate the redshiftmeta.numberintnullableMembMembership flag (3)meta.code.errorchar