J/MNRAS/512/4171ivo://CDS.VizieR/J/MNRAS/512/4171doi:10.26093/cds/vizier.75124171CDSYang Y.Hammer F.Jiao Y.Pawlowski M.S.2025-08-26T20:10:53Z2025-03-28T14:01:22ZCDS support team

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

cds-question@unistra.frdwarf-galaxiesgalaxieslocal-groupgiant-starsg-starsastrometryvisible-astronomyphotometryWe have studied the extent of the Red Giant Branch stellar population in the Fornax dwarf spheroidal galaxy using the spatially extended and homogeneous data set from Gaia EDR3. Our pre-selection of stars belonging to Fornax is based on their proper motions, parallaxes, and colour-magnitude diagram. The latter criteria provide a Fornax star sample, which we further restrict by colour and magnitude to eliminate contaminations due to either Milky Way stars or QSOs. The precision of the data has been sufficient to reach extremely small contaminations (0.02-0.3 per cent), allowing us to reach to a background level 12 magnitudes deeper than the central surface brightness of Fornax. We discover a break in the density profile, which reveals the presence of an additional component that extents 2.1 degree in radius, i.e. 5.4 kpc, and almost seven times the half-light radius of Fornax. The extended new component represents 10 per cent of the stellar mass of Fornax, and behaves like an extended halo. The absence of tidally elongated features at such an unprecedented depth (equivalent to 37.94 +/- 0.16 mag arcsec^-2^ in V-band) rules out a possible role of tidal stripping. We instead suggest that Fornax is likely at first infall, and has lost its gas very recently, which consequently leads to a lack of gravity implying that residual stars have spherically expanded to form the newly discovered stellar halo of Fornax.2022MNRAS.512.4171Yhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/512/4171CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/144/4 : Properties of dwarf galaxies in the Local GroupJ/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)J/A+A/649/A7 : MC structure and properties (Gaia Collaboration+, 2021)J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)J/MNRAS/453/690 : Fornax VST ATLAS catalogue (Bate+, 2015)J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)I/350 : Gaia EDR3 (Gaia Collaboration, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/512/4171https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/512/4171http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/512/4171https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/512/4171https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/512/4171http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/512/4171GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/512/4171/s0cand (*Fornax member candidates S_0_ final sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/512/4171/s0cand?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/512/4171/s0cand?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/512/4171/s0cand?GETtext/xml+votable180.050000true33.8368492457028-29.69894128210090.005555555555555556Cone search capability for table J/MNRAS/512/4171/s1cand (*Fornax member candidates S_1_ final sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/512/4171/s1cand?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/512/4171/s1cand?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/512/4171/s1cand?GETtext/xml+votable180.050000true33.3337980473682-28.52313915873310.005555555555555556Cone search capability for table J/MNRAS/512/4171/s2cand (*Fornax member candidates S_2_ final sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/512/4171/s2cand?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/512/4171/s2cand?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/512/4171/s2cand?GETtext/xml+votable180.050000true35.5747036258477-28.10571613387210.0055555555555555563/538 549 557 560 562 4/2111 2158 2195 2201 2203-2205 2207 2225 2244-2245 2247 2252-2253 2272-2273 2276 5/8439 8441-8443 8624 8626-8627 8636 8638-8639 8773 8775 8779 8801 8803 8809-8811 8824-8825 8827 8897 8899 8908-8909 8984-8986 9016-9018 9020-9022 9026 9034 9056 9096 9098-9102 9108 9112 6/33725 33727 33743 33750-33751 33753-33755 33762-33763 34366-34367 34500 34502-34503 34514 34520 34522-34523 34526 34548 34550-34551 34730 35087 35091 35096-35098 35109 35111 35203 35209 35211 35233-35235 35304-35305 35307 35584-35585 35587 35593 35621 35644-35645 35647 35780-35781 35793 35796-35797 35948-35950 36077-36079 36092 36094-36096 36098 36128 36130-36131 36232-36234 36256 36258 36264 36388-36390 36412-36414 36436 36440-36441 36452-36453 36456 36480-36481 36484-364851.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/512/4171?format=asciiOpticaldefaultJ/MNRAS/512/4171/s0cand*Fornax member candidates S_0_ final samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaEDR3Id of sources in Gaia EDR3 (source_id)meta.id;meta.mainRA_ICRSRight ascension (ICRS) at Ep=2016.0 from Gaia EDR3 (ra)degpos.eq.ra;meta.mainindexede_RA_ICRSError of RAdeg Gaia EDR3 (ra_error)degstat.error;pos.eq.radoubleDE_ICRSDeclination (ICRS) at Ep=2016.0 from Gaia EDR3 (dec)degpos.eq.dec;meta.mainindexede_DE_ICRSError of DEdeg Gaia EDR3 (dec_error)degstat.error;pos.eq.decdoubleGmagG-band mean magnitude (Vega) from Gaia EDR3 (phot_g_mean_mag)magphot.mag;em.opt.VdoubleBP-RPBP-RP colour from Gaia EDR3 (bp_rp)magphot.color;em.opt.B;em.opt.RdoublexJ/MNRAS/512/4171/s1cand*Fornax member candidates S_1_ final samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaEDR3Id of sources in Gaia EDR3 (source_id)meta.id;meta.mainRA_ICRSRight ascension (ICRS) at Ep=2016.0 from Gaia EDR3 (ra)degpos.eq.ra;meta.mainindexede_RA_ICRSError of RAdeg Gaia EDR3 (ra_error)degstat.error;pos.eq.radoubleDE_ICRSDeclination (ICRS) at Ep=2016.0 from Gaia EDR3 (dec)degpos.eq.dec;meta.mainindexede_DE_ICRSError of DEdeg Gaia EDR3 (dec_error)degstat.error;pos.eq.decdoubleGmagG-band mean magnitude (Vega) from Gaia EDR3 (phot_g_mean_mag)magphot.mag;em.opt.VdoubleBP-RPBP-RP colour from Gaia EDR3 (bp_rp)magphot.color;em.opt.B;em.opt.RdoublexJ/MNRAS/512/4171/s2cand*Fornax member candidates S_2_ final sampleSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaEDR3Id of sources in Gaia EDR3 (source_id)meta.id;meta.mainRA_ICRSRight ascension (ICRS) at Ep=2016.0 from Gaia EDR3 (ra)degpos.eq.ra;meta.maine_RA_ICRSError of RAdeg Gaia EDR3 (ra_error)degstat.error;pos.eq.radoubleDE_ICRSDeclination (ICRS) at Ep=2016.0 from Gaia EDR3 (dec)degpos.eq.dec;meta.maine_DE_ICRSError of DEdeg Gaia EDR3 (dec_error)degstat.error;pos.eq.decdoubleGmagG-band mean magnitude (Vega) from Gaia EDR3 (phot_g_mean_mag)magphot.mag;em.opt.VdoubleBP-RPBP-RP colour from Gaia EDR3 (bp_rp)magphot.color;em.opt.B;em.opt.RdoublexJ/MNRAS/512/4171/s0densSurface density profile of S_0_ final samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRmeanJ/MNRAS/512/4171/s1densSurface density profile of S_1_ final samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRmeanJ/MNRAS/512/4171/s2densSurface density profile of S_2_ final samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRmean