J/ApJ/944/43ivo://CDS.VizieR/J/ApJ/944/43doi:10.26093/cds/vizier.19440043CDSSimon J.D.Brown T.M.Mutlu-Pakdil B.Ji A.P.Drlica-Wagner A.,Avila R.J.Martinez-Vazquez C.E.Li T.S.Balbinot E.Bechtol K.,Frebel A.Geha M.Hansen T.T.James D.J.Pace A.B.Aguena M.,Alves O.Andrade-Oliveira F.Annis J.Bacon D.Bertin E.Brooks D.,Burke D.L.Rosell A.C.Kind M.C.Carretero J.Costanzi M.,da Costa L.N.De Vicente J.Desai S.Doel P.Everett S.Ferrero I.,Frieman J.Garcia-Bellido J.Gatti M.Gerdes D.W.Gruen D.,Gruendl R.A.Gschwend J.Gutierrez G.Hinton S.R.Hollowood D.L.,Honscheid K.Kuehn K.Kuropatkin N.Marshall J.L.Mena-Fernandez J.,Miquel R.Palmese A.Paz-Chinchon F.Pereira M.E.S.Pieres A.,Malagon A.A.P.Raveri M.Rodriguez-Monroy M.Sanchez E.Santiago B.,Scarpine V.Sevilla-Noarbe I.Smith M.Suchyta E.Swanson M.E.C.,Tarle G.To C.Vincenzi M.Weaverdyck N.Wilkinson R.D.2025-03-07T20:10:39Z2025-02-25T16:40:20ZCDS support team

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

cds-question@unistra.frgalaxiesphotometrylocal-grouphst-photometryvisible-astronomyThe ultra-faint dwarf galaxy Reticulum II (Ret II) exhibits a unique chemical evolution history, with 72_-12_^+10^% of its stars strongly enhanced in r-process elements. We present deep Hubble Space Telescope photometry of Ret II and analyze its star formation history. As in other ultra-faint dwarfs, the color-magnitude diagram is best fit by a model consisting of two bursts of star formation. If we assume that the bursts were instantaneous, then the older burst occurred around the epoch of reionization, forming ~80% of the stars in the galaxy, while the remainder of the stars formed ~3Gyr later. When the bursts are allowed to have nonzero durations, we obtain slightly better fits. The best-fitting model in this case consists of two bursts beginning before reionization, with approximately half the stars formed in a short (100Myr) burst and the other half in a more extended period lasting 2.6Gyr. Considering the full set of viable star formation history models, we find that 28% of the stars formed within 500+/-200Myr of the onset of star formation. The combination of the star formation history and the prevalence of r-process-enhanced stars demonstrates that the r-process elements in Ret II must have been synthesized early in its initial star-forming phase. We therefore constrain the delay time between the formation of the first stars in Ret II and the r-process nucleosynthesis to be less than 500Myr. This measurement rules out an r-process source with a delay time of several Gyr or more, such as GW170817.2023ApJ...944...43Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/944/43CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/129/2714 : JHK photometry of M92 variable stars (Del Principe+, 2005)J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013)J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)J/ApJ/808/95 : Spectroscopy of Reticulum II (Simon+, 2015)J/ApJ/802/93 : Abundance analysis of 5 stars in Sculptor (Simon+, 2015)J/ApJ/830/93 : Abund. of the Ret II brightest red giant members (Ji+, 2016)J/ApJ/817/41 : Abundances of 4 metal-poor red giants in BooII (Ji+, 2016)J/AJ/151/82 : The 4 brightest red giants in Ret 2 (Roederer+, 2016)J/ApJ/838/44 : Abund. of the brightest member of Tuc III (Hansen+, 2017)J/ApJ/850/137 : ISLAndS project. III. Var. stars (Martinez-Vazquez+, 2017)J/ApJ/838/11 : Member stars in the MW satellite Tucana III (Simon+, 2017)J/ApJ/863/25 : Deep Magellan obs. of 4 MW satellites (Mutlu-Pakdil+, 2018)J/ApJ/882/40 : Lanthanide fraction in metal-poor stars (Ji+, 2019)J/ApJ/882/177 : Abundances of 4 member stars of Tucana III (Marshall+, 2019)J/ApJ/885/53 : Sp. & HST phot. of galaxy Leo V (Mutlu-Pakdil+, 2019)J/ApJ/903/88 : Ions individual abund. in LAMOST J1109+0754 (Mardini+, 2020)J/MNRAS/499/4040 : RR Lyrae pop. in the Draco dwarf galaxy (Muraveva+, 2020)J/ApJ/902/106 : HST Gaia data of Hercules dwarf gal. (Mutlu-Pakdil+, 2020)J/ApJ/906/96 : Dwarfs gal. in DC Justice League Simul. (Applebaum+, 2021)J/AJ/162/229 : 13 Magellanic Clouds metal-poor stars (Reggiani+, 2021)J/ApJ/908/18 : HST stellar photometry of Eridanus II (Simon+, 2021)J/A+A/657/A54 : Local Group Gaia eDR3 systemic motions (Battaglia+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/944/43https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/944/43http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/944/43https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/944/43https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/944/43http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/944/43GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/944/43/table1 (Ret II stellar photometry)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/944/43/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/944/43/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/944/43/table1?GETtext/xml+votable180.050000true54.12315806-53.961301940.0055555555555555566/33626-336272.3657755224268815e-19 3.5452907792336973e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/944/43?format=asciiOpticaldefaultJ/ApJ/944/43/table1Ret II stellar photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/17947] Stellar index numbermeta.id;meta.mainintRAJ2000[53.68/54.2] Right Ascension (J2000) (1)degpos.eq.ra;meta.mainindexedDEJ2000[-54.2/-53.9] Declination (J2000) (1)degpos.eq.dec;meta.mainindexedF606mag[18.34/28.64] HST/ACS F606W band apparent magnitude (STMAG system)magphot.mag;em.opt.Rfloate_F606mag[0.001/0.3] Uncertainty in F606magmagstat.error;phot.mag;em.opt.RfloatF814mag[19/28.91] HST/ACS F814W band apparent magnitude (STMAG system)magphot.mag;em.opt.Ifloate_F814mag[0.001/0.3] Uncertainty in F814magmagstat.error;phot.mag;em.opt.Ifloat