J/MNRAS/488/2743ivo://CDS.VizieR/J/MNRAS/488/2743doi:10.26093/cds/vizier.74882743CDSTorrealba G.Belokurov V.Koposov S.E.Li T.S.Walker M.G.,Sanders J.L.Geringer-Sameth A.Zucker D.B.Kuehn K.Evans N.W.,Dehnen W.2024-08-20T20:12:03Z2023-02-03T14:28:11ZCDS support team

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

cds-question@unistra.frhalo-starsastrometryradial-velocityproper-motionseffective-temperaturemetallicityvisible-astronomyWe report the discovery of a Milky Way satellite in the constellation of Antlia. The Antlia 2 dwarf galaxy is located behind the Galactic disc at a latitude of b~11{deg} and spans 1.26{deg}, which corresponds to ~2.9kpc at its distance of 130kpc. While similar in spatial extent to the Large Magellanic Cloud, Antlia 2 is orders of magnitude fainter at M_V_=-9mag, making it by far the lowest surface brightness system known (at ~31.9mag/arcsec^2^), ~100 times more diffuse than the so-called ultra diffuse galaxies. The satellite was identified using a combination of astrometry, photometry, and variability data from Gaia Data Release 2, and its nature confirmed with deep archival DECam imaging, which revealed a conspicuous BHB signal. We have also obtained follow-up spectroscopy using AAOmega on the AAT, identifying 159 member stars, and we used them to measure the dwarf's systemic velocity, 290.9+/-0.5km/s, its velocity dispersion, 5.7+/-1.1km/s, and mean metallicity, [Fe/H]=-1.4. From these properties we conclude that Antlia 2 inhabits one of the least dense dark matter (DM) haloes probed to date. Dynamical modelling and tidal-disruption simulations suggest that a combination of a cored DM profile and strong tidal stripping may explain the observed properties of this satellite. The origin of this core may be consistent with aggressive feedback, or may even require alternatives to cold dark matter (such as ultra-light bosons).2019MNRAS.488.2743Thttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/488/2743CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/488/2743https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/488/2743http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/488/2743https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/488/2743https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/488/2743http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/488/2743GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/488/2743/table1 (Properties of the Antlia 2 dwarf)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/488/2743/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/488/2743/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/488/2743/table1?GETtext/xml+votable180.050000true143.8868-36.76730.005555555555555556Cone search capability for table J/MNRAS/488/2743/table2 (Results from the spectroscopic modelling)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/488/2743/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/488/2743/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/488/2743/table2?GETtext/xml+votable180.050000true144.41-36.76780.0055555555555555565/9656 6/38603 38628 38630 38632-38633https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/488/2743?format=asciiOpticaldefaultJ/MNRAS/488/2743/table1Properties of the Antlia 2 dwarfrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameDwarf galaxy namemeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.maine_RAJ2000Error on RAdegdegstat.error;pos.eq.rafloatDEJ2000Declination (J2000)degpos.eq.dec;meta.maine_DEJ2000Error on DEdegdegstat.error;pos.eq.decfloatGLONGalactic longitudedegpos.galactic.lone_GLONError on GLONdegstat.errorfloatGLATGalactic latitudedegpos.galactic.latfloate_GLATError on GLATdegstat.errorfloatm-MDistance modulusmagphot.mag.distModfloate_m-MError on m-Mmagstat.errorfloatDistDistance from the sunkpcpos.distanceinte_DistError on Distkpcstat.errorintrhdegHalf-light radius in degreesdegphys.angSize;srcfloate_rhdegError on rhdegdegstat.errorfloat1-b/aOne minus the axial ratio b/aphys.size.axisRatiofloate_1-b/aError on 1-b/astat.errorfloatPAPosition angledegpos.posAnginte_PAError on PAdegstat.errorintVMAGAbsolute V magnitudemagphys.magAbsfloate_VMAGError on VMAGmagstat.errorfloatmurhSurface brightness within r<rhmag.arcsec**-2phot.mag.sbfloate_murhError on murhmag.arcsec**-2stat.errorfloat[Fe/H]Iron to hydrogen abundance ratiophys.abund.Fe;arith.ratiofloate_[Fe/H]Error on [Fe/H]stat.error;phys.abund.Fefloatsig[Fe/H]Standard deviation of [Fe/H]stat.stdev;phys.abund.Fefloate_sig[Fe/H]Error on sig[Fe/H]stat.error;phys.abund.FefloatHRVHeliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRVError on HRVkm/sstat.errorfloatRVgsrRadial velocity in the galactic system of restkm/sphys.veloc;pos.galactocentricfloate_RVgsrError on RVgsrkm/sstat.errorfloatf_RVgsr[b] Flag on RVgsr (1)meta.codecharsigRVGlobal velocity dispersionkm/sphys.veloc.dispersionfloate_sigRVError on sigRVkm/sstat.errorfloatpmRAProper motion on right ascensionmas/yrpos.pm;pos.eq.rafloate_pmRAError on pmRAmas/yrstat.error;pos.pm;pos.eq.rafloatf_pmRA[a] Flag on pmRA (2)meta.codecharpmDEProper motion in declinationmas/yrpos.pm;pos.eq.decfloate_pmDEError on pmDEmas/yrstat.error;pos.pm;pos.eq.decfloatf_pmDE[a] Flag on pmDE (2)meta.codecharMrhGalaxy Mass within rh1e+07solMassphys.massfloatM/LMass to luminosity ratiosolMass/solLumphys.composition.massLightRatiointSimbadSimbad column added by the CDSmeta.ref.urlchare_M/LError on M/LsolMass/solLumstat.errorintrhpcHalf-light radius in parsecspcphys.size.radiusinte_rhpcError on rhpcpcstat.errorinte_MrhError on Mrh1e+07solMassstat.errorfloatM1.8rhGalaxy Mass within 1.8rh1e+07solMassphys.massfloate_M1.8rhError on M1.8rh1e+07solMassstat.errorfloatM*Total stellar mass100000solMassphys.massfloate_M*Error on M*100000solMassstat.errorfloatJ/MNRAS/488/2743/table2Results from the spectroscopic modellingNameStar identifier (Antlia2_NNN)meta.id;meta.maincharSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainHRVHeliocentric radial velocitykm/sspect.dopplerVeloc;pos.heliocentricfloate_HRVError on HRVkm/sstat.errorfloat[Fe/H]Iron to hydrogen abundance ratiophys.abund.Fe;arith.ratiofloate_[Fe/H]Error on [Fe/H]stat.error;phys.abund.FefloatloggSurface gravitylog(cm.s**-2)phys.gravityfloate_loggError on logglog(cm.s**-2)stat.errorfloatTeffEffective temperatureKphys.temperature.effectiveinte_TeffError on TeffKstat.error;phys.temperature.effectiveint