J/A+A/706/A253ivo://CDS.VizieR/J/A+A/706/A253CDSJimenez-Arranz O.Lilleengen S.Petersen M.S.2026-03-02T06:25:50Z2026-02-17T11:19:50ZCDS support team

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

cds-question@unistra.frsurveysmilky-way-galaxyvisible-astronomyWhile the influence of the Large Magellanic Cloud (LMC) on Milky Way stellar streams has been extensively studied, streams associated with the Clouds themselves have received far less attention. Beyond the Magellanic Stream, only four stellar stream candidates (S1 to S4) associated with the Clouds have been reported. We focus on the S3 stream, a long (about 30 degrees) and narrow (about 1.2 degrees) stellar structure located at distances of 60 to 80kpc and nearly aligned with the LMC. Our goals are threefold: to validate the stream through a kinematic analysis of S3 candidates using Gaia DR3 data; to enlarge the sample of potential members using machine-learning methods; and to model the stream in order to test its association with either the Milky Way or the LMC. We selected new S3 candidates using a supervised neural network classifier trained on Gaia DR3 astrometry and photometry, and further reduced contamination by applying a polygon selection in proper-motion space. To investigate the origin of S3, we evolved stream models in time-dependent and deforming Milky Way and LMC haloes, accounting for the dynamical effects of the Milky Way-LMC interaction. We identify 2177 S3 stream candidates with P>0.5 that satisfy the proper-motion polygon selection, from which we define a high-confidence subsample of 1542 new S3 stream candidates using a probability threshold P_cut_=0.8. We also provide a catalogue of 440 potential S3 red clump stars, which are particularly valuable targets for spectroscopic follow-up due to their well-defined luminosities and their ability to yield precise distance estimates. Both the dynamical modelling and a comparison between the closest approach distances and velocities of S3 stars relative to the LMC escape velocity indicate that S3 is unlikely to originate from the LMC. Instead, S3 is best interpreted as a distant Milky Way stellar stream located at approximately 75kpc. S3 is therefore the most distant known extended Milky Way stellar stream, with a length of about 30 degrees and a thickness of 3 to 4 degrees, corresponding to a physical width of roughly 4 to 5kpc. This makes S3 one of the thickest stellar streams discovered to date and a unique probe of the outer Milky Way halo and of the recent dynamical influence of the LMC.2026A&A...706A.253Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/706/A253CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. 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Should Not be used for identification.meta.recordintGaiaDR3Gaia DR3 unique source identifier (source_id)meta.id;meta.mainRA_ICRSRight ascension (ICRS) (ra)degpos.eq.ra;meta.mainDE_ICRSDeclination (ICRS) (dec)degpos.eq.dec;meta.mainplxParallax (parallax)maspos.parallax.trigdoublee_plxParallax uncertainty (parallax_error)masstat.error;pos.parallaxdoublepmRAProper motion in right ascension (includes cos(dec) factor) (pmra)mas/yrpos.pm;pos.eq.radoublee_pmRAUncertainty on pmra (pmra_error)mas/yrstat.error;pos.pm;pos.eq.radoublepmDEProper motion in declination (pmdec)mas/yrpos.pm;pos.eq.decdoublee_pmDEUncertainty on pmdec (pmdec_error)mas/yrstat.error;pos.pm;pos.eq.decdoubleGmagMean G-band magnitude (phot_g_mean_mag)magphot.mag;em.optdoubleBPmagMean BP-band magnitude (phot_bp_mean_mag)magphot.mag;em.opt.BdoubleRPmagMean RP-band magnitude (phot_rp_mean_mag)magphot.mag;em.opt.RdoublePmemb[0/1] S3 membership probability (P) (1)stat.probabilitydoubleisRCcandRed clump candidate flag (is_RC_candidate) (2)meta.codechar