J/ApJ/944/1ivo://CDS.VizieR/J/ApJ/944/1doi:10.26093/cds/vizier.19440001CDSDey A.Najita J.R.Koposov S.E.Josephy-Zack J.Maxemin G.Bell E.F.,Poppett C.Patel E.Beraldo Silva L. eRaichoor A.Schlegel D.,Lang D.Meisner A.Myers A.D.Aguilar J.Ahlen S.Allende Prieto C.,Brooks D.Cooper A.P.Dawson K.S.de la Macorra A.Doel P.,Font-Ribera A.Garcia-Bellido J.Gontcho Gontcho S. AGuy J.,Honscheid K.Kehoe R.Kisner T.Kremin A.Landriau M.Le Guillou L.,Levi M.E.Li T.S.Martini P.Miquel R.Moustakas J.Nie J.,Palanque-Delabrouille N.Prada F.Schlafly E.F.Sharples R.M.,Tarle G.Ting Y.-S.Tyas L.Valluri M.Wechsler R.H.Zou H.2026-05-12T20:05:24Z2025-02-25T09:44:20ZCDS support team

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

cds-question@unistra.frgalaxiesvisible-astronomyspectroscopyinfrared-photometrybroad-band-photometrymetallicityredshiftedradial-velocityh-ii-regionsplanetary-nebulaequasarsWe present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger-a galactic immigration event-in exquisite detail. Of the 11416 sources studied in 3.75hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1-2Gyr ago. Significant numbers of metal-rich stars ([Fe/H]{>}-0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125kpc to be log_10_M_NFW_(<125kpc)/M_{sun}_=11.80_-0.10_^+0.12^. The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.2023ApJ...944....1Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/944/1CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)II/363 : The band-merged unWISE Catalog (Schlafly+, 2019)II/365 : The CatWISE2020 cat. (updated version 28-Jan-2021) (Marocco+, 2021)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)VII/292 : DESI Legacy Imaging Surveys DR8 photometric redshifts (Duncan, 2022)J/MNRAS/369/120 : Kinematic survey of planetary nebulae in M31 (Merrett+, 2006)J/A+A/471/127 : Revised Bologna Catalog of M31 clusters, V.3 Galleti+, 2007)J/ApJ/736/146 : Radial velocities of stars in Bootes I (Koposov+, 2011)J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)J/ApJ/758/133 : Metallicity profile of M31 HII regions & PNe (Sanders+, 2012)J/ApJ/749/77 : MW halo. III. Statistical abundances (Schlaufman+, 2012)J/ApJ/776/80 : PAndAS view of Andromeda satellites. I. (Martin+, 2013)J/AJ/145/159 : LAMOST. II. ugriz photometry of 526 new quasars (Huo+, 2013)J/other/RAA/15.1392 : LAMOST globular clusters in M 31 and M 33 (Chen+, 2015)J/other/RAA/15.1438 : LAMOST new QSOs in M31 and M33 vicinity (Huo+, 2015)J/ApJ/824/42 : Star clusters in M31. VII. GCl RVs (Caldwell+, 2016)J/ApJ/833/167 : PAndAS view of Andromeda satellites. II. (Martin+, 2016)J/AJ/152/45 : LAMOST survey of star clusters in M31. II. (Chen+, 2016)J/ApJ/868/55 : Large-scale structure of M31 halo. II. (McConnachie+, 2018)J/ApJ/883/128 : alpha & Fe in the giant stellar stream (Gilbert+, 2019)J/ApJ/889/177 : RGB abund. in the disk, stream & halo of M31 (Escala+, 2020)J/ApJ/902/51 : Abundances for M31 RGB stars from Keck/DEIMOS (Escala+, 2020)J/ApJS/247/47 : UV survey of M31 with UVIT on AstroSat (Leahy+, 2020)J/AJ/159/46 : Abundances of 416 stars in 5 dSphs of M31 (Kirby+, 2020)J/A+A/645/A115 : 346 M31 star clusters and their parameters (Wang+, 2021)J/A+A/658/A51 : New M31 star cluster candidates (Wang+, 2022)J/AJ/164/20 : RGB RVs in M31 northeast shelf fields (Escala+, 2022)J/other/Nat/603.599 : 247014 subgiant stars data (Xiang+, 2022)http://www.desi.lbl.gov/ : DESI homepagehttp://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/pandas/csky.html :https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/944/1https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/944/1http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/944/1https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/944/1https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/944/1http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/944/1GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/944/1/table2 (M31 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/1/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/1/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/1/table2?GETtext/xml+votable180.050000true9.737130140.21782330.005555555555555556Cone search capability for table J/ApJ/944/1/table3 (M31 HII, PNe, and GC targets)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/1/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/1/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/1/table3?GETtext/xml+votable180.050000true10.23740.33580.005555555555555556Cone search capability for table J/ApJ/944/1/table6 (QSOs behind M31; see Appdendix A)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/1/table6?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/1/table6?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/1/table6?GETtext/xml+votable180.050000true10.037391840.10502910.005555555555555556Cone search capability for table J/ApJ/944/1/table7 (Galaxies behind M31; see Appdendix A)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/1/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/1/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/1/table7?GETtext/xml+votable180.050000true10.221126640.01216250.005555555555555556Cone search capability for table J/ApJ/944/1/mcat (DESI M31 measurement catalog (DESI_M31_MEASUREMENT_CATALOG.fits); see Appendix C)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/1/mcat?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/1/mcat?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/1/mcat?GETtext/xml+votable180.050000true9.737130140.21782330.0055555555555555565/653-655 666 677 6/2609-2611 2668 2670 2705 2707 2716 2752-2754 27561.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/944/1?format=asciiOpticalInfrareddefaultJ/ApJ/944/1/table2M31 starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/7348] Internal running index identifiermeta.id;meta.mainintRAJ2000[8/14] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[37/44] Declination (J2000)degpos.eq.dec;meta.mainVlos[-639/270] Line of sight heliocentric velocitykm/sphys.velocfloate_Vlos[0/150] Uncertainty in Vloskm/sstat.error;phys.velocfloat[Fe/H][-4/1] Spectroscopic estimate of [Fe/H]log(Sun)phys.abund.FefloatSimbadSimbad column added by the CDSmeta.ref.urlchare_[Fe/H][0/5.6]? Uncertainty in [Fe/H]log(Sun)stat.error;phys.abund.FefloatnullableTeff[2300/13755] Effective temperatureKphys.temperature.effectivefloate_Teff[0.2/4119]? Uncertainty in TeffKstat.error;phys.temperature.effectivefloatnullablelogg[-0.5/6] log surface gravitylog(cm.s**-2)phys.gravityfloate_logg[0/4] Uncertainty in log(g)log(cm.s**-2)stat.error;phys.gravityfloatGmag[11/21.6]? Gaia DR2 G band apparent magnitudemagphot.mag;em.optfloatnullablegmag[17.38/27.33]? PAndAS g-band apparent magnitudemagphot.mag;em.opt.Bfloatnullableimag[16.86/22.8]? PAndAS i-band apparent magnitudemagphot.mag;em.opt.IfloatnullableANameAlternate target name from Gaia DR2 or PAndASmeta.idcharJ/ApJ/944/1/table3M31 HII, PNe, and GC targetsSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/179] Internal running index identifiermeta.id;meta.mainintRAJ2000[8.9/13.5] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[39.9/42.6] Declination (J2000)degpos.eq.dec;meta.mainVlos[-713/54] Line of sight heliocentric velocitykm/sphys.velocfloate_Vlos[0/17] Uncertainty in Vloskm/sstat.error;phys.velocfloatClassTarget class (1)src.classcharGmag[15.99/22]? Gaia DR2 G band apparent magnitudemagphot.mag;em.optfloatnullablegmag[16/22.8]? PAndAS g-band apparent magnitudemagphot.mag;em.opt.Bfloatnullableimag[15.2/35]? PAndAS i-band apparent magnitudemagphot.mag;em.opt.IfloatnullableANameAlternate target name (2)meta.idcharJ/ApJ/944/1/table6QSOs behind M31; see Appdendix ASimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/184] Internal running index identifiermeta.id;meta.mainintRAJ2000[8/14] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[37/44] Declination (J2000)degpos.eq.dec;meta.mainz[0.09/3.5] Spectroscopic redshiftsrc.redshiftfloatGmag[17.68/21.1]? Gaia DR2 G band apparent magnitudemagphot.mag;em.optfloatnullablegmag[17.7/24.25]? PAndAS g-band apparent magnitudemagphot.mag;em.opt.Bfloatnullableimag[17.64/34.8]? PAndAS i-band apparent magnitudemagphot.mag;em.opt.IfloatnullableGaiaDR3? The Gaia DR3 identifiermeta.idnullableJ/ApJ/944/1/table7Galaxies behind M31; see Appdendix ArecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/684] Internal running index identifiermeta.id;meta.mainintRAJ2000[8.3/14] Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000[37/44] Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainSimbadSimbad column added by the CDSmeta.ref.urlcharz[0.03/1.6] Spectroscopic redshiftsrc.redshiftfloatgmag[18.34/27.34]? PAndAS g-band apparent magnitudemagphot.mag;em.opt.Bfloatnullableimag[17/22.81]? PAndAS i-band apparent magnitudemagphot.mag;em.opt.IfloatnullableANameAlternate name, where availablemeta.idcharJ/ApJ/944/1/mcatDESI M31 measurement catalog (DESI_M31_MEASUREMENT_CATALOG.fits); see Appendix CHRVRed[-600/1037934] Heliocentric radial velocity from the DESI Redrock pipeline (VRAD_REDROCK)km/sspect.dopplerVeloc;pos.heliocentricdoublee_HRVRed[0.04/187] HRVRed uncertainty (VRAD_REDROCK_ERR)km/sstat.error;spect.dopplerVeloc;pos.heliocentricfloatf_HRVRed[0/1056] Warning flags for Redrock pipeline reductions (0=good) (REDROCK_ZWARN)meta.code;spect.dopplerVeloc;pos.heliocentricintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordinttargetIDDESI target identification (TARGETID)meta.id;meta.mainDupDESI targetID of the duplicate entry for this source if one exists; 0 otherwise (DUPLICATE)meta.id.assocPrim1=Primary entry; O=otherwise; only for duplicate entries (PRIMARY)meta.codeintRAJ2000[8/14] Right ascension (J2000) (RA)degpos.eq.ra;meta.mainindexedDEJ2000[37/44] Declination (J2000) (DEC)degpos.eq.dec;meta.mainindexedHRVBest[-713/1037934] "Best" heliocentric radial velocity (VRAD_BEST)km/sspect.dopplerVeloc;pos.heliocentric;meta.modelleddoublee_HRVBest[0.02/187] HRVBest uncertainty (VRAD_BEST_ERR)km/sstat.error;spect.dopplerVeloc;pos.heliocentricfloatHRV[-1500/1500] Heliocentric radial velocity (VRAD)km/sspect.dopplerVeloc;pos.heliocentricdoublee_HRV[0.02/1865] HRV uncertainty (VRAD_ERR)km/sstat.error;spect.dopplerVeloc;pos.heliocentricdoubleSkew[-85/33] Skew on the heliocentric radial velocity from DESI's RV Pipeline (VRAD_SKEW)km/sstat.fit.param;phys.velocfloatKurt[1/8567] Kurtosis on the heliocentric radial velocity from DESI's RV Pipeline (VRAD_KURT)km/sstat.fit.param;phys.velocdoublelogg[-0.51/6] Log of surface gravity (LOGG)log(cm.s**-2)phys.gravityfloate_logg[0.0001/4] logg uncertainty (LOGG_ERR)log(cm.s**-2)stat.error;phys.gravitydoubleTeff[2300/15000] Effective temperature (TEFF)Kphys.temperature.effectivefloate_Teff[0.16/4119]? Teff uncertainty (TEFF_ERR)Kstat.error;phys.temperature.effectivefloatnullable[Fe/H][-4/1] Metallicity (FEH)phys.abund.Fefloate_[Fe/H][0.00013/6]? [Fe/H] Uncertainty (FEH_ERR)stat.error;phys.abund.Fedoublenullablef_RVS[0/7] Warning flags for the RVS pipeline reductions (0=good) (RVS_WARN)meta.codeintClassSelection class(es) for the target (CLASS)meta.notecharANameAlternate designation of the target (DESIGNATION)meta.idcharGaiaDR3? Gaia DR3 unique identification number (GDR3_ID)meta.id.crossnullablespTypeSpectroscopic type: STAR, GALAXY or QSO (SPECTYPE)src.class.starGalaxycharTILEIDDESI Tiles contributing to the spectrum (TILEID)meta.id;obscharSNB[-1.1/241] Signal-to-noise ratio in the blue arm of the DESI spectrograph (SN_B)stat.snr;em.opt.BdoubleSNR[-0.9/339] Signal-to-noise ratio in the red arm of the DESI spectrograph (SN_R)stat.snr;em.opt.RdoubleSNZ[0/411] Signal-to-noise ratio in the NIR arm of the DESI spectrograph (SN_Z)stat.snrdoubleHRVvi[-10000/1037974] Heliocentric radial velocity from the Visual Inspection (VRAD_VI)km/sspect.dopplerVeloc;pos.heliocentricdoubleq_HRVvi[-9/4] Quality flag from the Visual Inspection (>=3 is good; <=2 is bad; <0 is not inspected) (VI_QUALITY)meta.code.qual;spect.dopplerVeloc;pos.heliocentricintspTypeVISpectral type from the Visual Inspection ("STAR", "GALAXY" or "QSO"; blank if unknown) (VI_SPECTYPE)src.class.starGalaxycharDist[0.02/4.2] Projected radial distance from the center of M31 (M31DIST)degpos.distancefloatGmag[0/22]? Gaia DR3 G-band magnitude (GAIA_G)magphot.mag;em.optfloatnullablegmag[16/35.5]? PAndAS g-band magnitude (PANDAS_G)magphot.mag;em.opt.Bfloatnullableimag[15.2/35]? PAndAS i-band magnitude (PANDAS_I)magphot.mag;em.opt.Ifloatnullablezmag[0.07/21.6]? Predicted Legacy Surveys z-band AB magnitude (PRED_Z)magphot.mag;em.IR.NIRfloatnullablexi[-2/2.4] Standard {xi} coordinate in frame centered on M31 (XI)degpos.frame;posfloateta[-4.2/2.5] Standard {eta} coordinate in frame centered on M31 (ETA)degpos.frame;posfloatthetaPolar angle centered on M31 and measured clockwise from the west (as in Figures 6, 7, 11, and 12) (THETA)degpos.posAngfloat