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Kinematics and Chemistry of Recently Discovered Reticulum 2 and Horologium 1 Dwarf Galaxies

hal.structure.identifierInstitute of Astronomy [Cambridge]
dc.contributor.authorKOPOSOV, Sergey
dc.contributor.authorCASEY, Andrew
dc.contributor.authorBELOKUROV, Vasily
dc.contributor.authorLEWIS, James
dc.contributor.authorGILMORE, Gerard
dc.contributor.authorWORLEY, Clare
dc.contributor.authorHOURIHANE, Anna
dc.contributor.authorRANDICH, S.
dc.contributor.authorBENSBY, T.
hal.structure.identifierINAF - Osservatorio Astronomico di Bologna [OABO]
dc.contributor.authorBRAGAGLIA, A.
dc.contributor.authorBERGEMANN, M.
dc.contributor.authorCARRARO, G.
dc.contributor.authorCOSTADO, M.
dc.contributor.authorFLACCOMIO, E.
hal.structure.identifierGalaxies, Etoiles, Physique, Instrumentation [GEPI]
dc.contributor.authorFRANÇOIS, P.
hal.structure.identifierUppsala University
dc.contributor.authorHEITER, U.
hal.structure.identifierJoseph Louis LAGRANGE [LAGRANGE]
dc.contributor.authorHILL, V.
hal.structure.identifierM2A 2014
dc.contributor.authorJOFRE, P.
dc.contributor.authorLANDO, C.
hal.structure.identifierINAF - Osservatorio Astrofisico di Catania [OACT]
dc.contributor.authorLANZAFAME, A.
hal.structure.identifierJoseph Louis LAGRANGE [LAGRANGE]
dc.contributor.authorLAVERNY, P. De
hal.structure.identifierIstituto Nazionale di Fisica Nucleare, Sezione di Milano [INFN]
dc.contributor.authorMONACO, L.
dc.contributor.authorMORBIDELLI, L.
hal.structure.identifierEuropean Southern Observatory [Santiago] [ESO]
dc.contributor.authorSBORDONE, L.
dc.contributor.authorMIKOLAITIS, Š.
hal.structure.identifierLund Observatory
dc.contributor.authorRYDE, N.
dc.date.issued2015-09-20
dc.identifier.issn0004-637X
dc.description.abstractEnWe report on VLT/GIRAFFE spectra of stars in two recently discovered ultra-faint satellites, Reticulum 2 and Horologium 1, obtained as part of the Gaia-ESO Survey. We identify 18 members in Reticulum 2 and five in Horologium 1. We find Reticulum 2 to have a velocity dispersion of {3.22}-0.49+1.64 {km} {{{s}}}-1, implying a mass-to-light ratio (M/L) of ̃500. The mean metallicity of Reticulum 2 is [{Fe}/{{H}}]=-2.46, with an intrinsic dispersion of ̃0.3 dex and α-enhancement of ̃0.4 dex. We conclude that Reticulum 2 is a dwarf galaxy. We also report on the serendipitous discovery of four stars in a previously unknown stellar substructure near Reticulum 2 with [{Fe}/{{H}}]̃ -2 and {V}{hel}̃ 220 {km} {{{s}}}-1, far from the systemic velocity of Reticulum 2. For Horologium 1 we infer a velocity dispersion of σ ≤ft(V\right)={4.9}-0.9+2.8 {km} {{{s}}}-1 and a M/L ratio of ̃600, leading us to conclude that Horologium 1 is also a dwarf galaxy. Horologium 1 is slightly more metal-poor than Reticulum 2 ([{Fe}/{{H}}]=-2.76) and is similarly α-enhanced: [α /{Fe}]̃ 0.3 {dex} with a significant spread of metallicities of 0.17 dex. The line-of-sight velocity of Reticulum 2 is offset by 100 km s-1 from the prediction of the orbital velocity of the Large Magellanic Cloud (LMC), thus making its association with the Cloud uncertain. However, at the location of Horologium 1, both the backward-integrated orbit of the LMC and its halo are predicted to have radial velocities similar to that of the dwarf. Therefore, it is possible that Horologium 1 is or once was a member of the Magellanic family.
dc.language.isoen
dc.publisherAmerican Astronomical Society
dc.subject.enGalaxies: abundances
dc.subject.enGalaxies: dwarf
dc.subject.enGalaxies: kinematics and dynamics
dc.subject.enGalaxy: halo
dc.subject.enGlobular clusters: general
dc.subject.enStars: abundances
dc.subject.enAstrophysics - Astrophysics of Galaxies
dc.title.enKinematics and Chemistry of Recently Discovered Reticulum 2 and Horologium 1 Dwarf Galaxies
dc.typeArticle de revue
dc.identifier.doi10.1088/0004-637X/811/1/62
dc.subject.halPlanète et Univers [physics]
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]
dc.identifier.arxiv1504.07916
bordeaux.journalThe Astrophysical Journal
bordeaux.page62
bordeaux.volume811
bordeaux.issue1
bordeaux.peerReviewedoui
hal.identifierhal-02453340
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-02453340v1
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