J/ApJ/816/L4ivo://CDS.VizieR/J/ApJ/816/L4doi:10.26093/cds/vizier.18169004CDSSesar B.Price-Whelan A.M.Cohen J.G.Rix H.-W.Pearson S.,Johnston K.V.Bernard E.J.Ferguson A.M.N.Martin N.F.Slater C.T.,Chambers K.C.Flewelling H.Wainscoat R.J.Waters C.2017-01-23T22:00:00Z2016-04-08T14:02:14ZCDS support team

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

cds-question@unistra.frhorizontal-branch-starsradial-velocityinfrared-photometryvisible-astronomyWide-band photometryThe Ophiuchus stellar stream presents a dynamical puzzle: its old stellar populations (~12Gyr) cannot be reconciled with (1) its orbit in a simple model for the Milky Way potential and (2) its short angular extent, both of which imply that the observed stream formed within the last <1Gyr. Recent theoretical work has shown that streams on chaotic orbits may abruptly fan out near their apparent ends; stars in these fans are dispersed in both position and velocity and may be difficult to associate with the stream. Here we present the first evidence of such stream-fanning in the Ophiuchus stream, traced by four blue horizontal branch stars beyond the apparent end of the stream. These stars stand out from the background by their high velocities (v_los_>230km/s) against ~40 other stars: their velocities are comparable to those of the stream, but would be exceptional if they were unrelated halo stars. Their positions and velocities are, however, inconsistent with simple extrapolation of the observed cold, high-density portion of the stream. These observations suggest that stream-fanning may be a real, observable effect and, therefore, that Ophiuchus may be on a chaotic orbit. They also show that the Ophiuchus stream is more extended and hence dynamically older than previously thought, easing the stellar population versus dynamical age tension.2016ApJ...816L...4Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/816/L4CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/813/83 : Multiple star formation in Ophiuchus (Cheetham+, 2015)J/ApJ/809/59 : Ophiuchus stellar stream with PS1 data (Sesar+, 2015)J/ApJ/775/63 : Gould's Belt VLA Survey. I. Ophiuchus complex (Dzib+, 2013)J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)J/ApJ/731/119 : BHB candidates in Sagittarius stream (Ruhland+, 2011)J/ApJ/703/1964 : Spectra of three nearby star-forming regions (Furlan+, 2009)J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/816/L4https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/816/L4http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/816/L4https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/816/L4https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/816/L4http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/816/L4GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/816/L4/table1 (Positions and velocities of observed candidate BHB stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/816/L4/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/816/L4/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/816/L4/table1?GETtext/xml+votable180.050000true243.19618-6.726220.0055555555555555565/7730 6/30879 30893 30901 30902 30903 30904 30905 30907 30908 30915 30924 30926 30944 30945 30946https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/816/L4?format=asciiInfraredOpticaldefaultJ/ApJ/816/L4/table1Positions and velocities of observed candidate BHB starsMm[NY] Member codemeta.codecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDSource identifier ("candNN" among 8 to 59)meta.id;meta.maincharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainVlos[-268/319] Heliocentric velocity {nu}_los_km/sphys.veloc;pos.heliocentricfloate_Vlos[1/12] Uncertainty in Vloskm/sstat.errorfloatgmag[15.2/16.7] PS1 g band magnitude; not corrected for extinctionmagphot.mag;em.opt.Bfloatimag[14.9/16.7] PS1 i band magnitude not corrected for extinctionmagphot.mag;em.opt.IfloatcHg[0.1/4]? Best-fit c value of Sersic profile to the H{gamma} linestat.fit.paramfloatnullablee_cHg[0.1/10.5]? The 1{sigma} uncertainty in cHgstat.errorfloatnullablebHg[0.2/11]? Best-fit b value of Sersic profile to the H{gamma} linestat.fit.paramfloatnullablee_bHg[0.2/0.8]? The 1{sigma} uncertainty in bHgstat.errorfloatnullableInstInstrument used in the observation (1)instr.setup;obscharBHB[ NY] BHB star flag (2)meta.codechar