J/ApJ/708/817ivo://CDS.VizieR/J/ApJ/708/817doi:10.26093/cds/vizier.17080817CDSFiorentino G.Monachesi A.Trager S.C.Lauer T.R.Saha A.,Mighell K.J.Freedman W.Dressler A.Grillmair C.Tolstoy E.2017-06-21T08:22:23Z2012-03-01T14:45:10ZCDS support team

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

cds-question@unistra.frhst-photometryvariable-starspopulation-ii-starsgalaxiesWe observed two fields near M32 with the Advanced Camera for Surveys/High Resolution Channel (ACS/HRC) on board the Hubble Space Telescope. The main field, F1, is 1.8' from the center of M32; the second field, F2, constrains the M31 background, and is 5.4' distant. Each field was observed for 16 orbits in each of the F435W (narrow B) and F555W (narrow V) filters. The duration of the observations allowed RR Lyrae stars to be detected. A population of RR Lyrae stars determined to belong to M32 would prove the existence of an ancient population in that galaxy, a subject of some debate. We detected 17 RR Lyrae variables in F1 and 14 in F2. A 1{sigma} upper limit of 6 RR Lyrae variables belonging to M32 is inferred from these two fields alone. Use of our two ACS/WFC parallel fields provides better constraints on the M31 background, however, and implies that 7^+4^_-3_ (68% confidence interval) RR Lyrae variables in F1 belong to M32. We have therefore found evidence for an ancient population in M32. It seems to be nearly indistinguishable from the ancient population of M31. The RR Lyrae stars in the F1 and F2 fields have indistinguishable mean V-band magnitudes, mean periods, distributions in the Bailey diagram, and ratios of RRc to RRtotal types. However, the color distributions in the two fields are different, with a population of red RRab variables in F1 not seen in F2. We suggest that these might be identified with the detected M32 RR Lyrae population, but the small number of stars rules out a definitive claim.2010ApJ...708..817Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/708/817CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/138/184 : RR Lyrae variables in 2 fields in M31 spheroid (Sarajedini+,J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)J/ApJ/532/308 : Hot Horizontal Branch Stars in the Core of M32 (Brown+ 2000)J/ApJ/504/113 : F175W and F275W photometry of M31 and M32 (Brown+, 1998)J/AJ/104/1349 : Infrared-luminous giants in M32 (Freedman, 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/708/817https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/708/817http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/708/817https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/708/817https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/708/817http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/708/817GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/708/817/rrlyr (RR Lyrae properties of Field 1 and Field 2)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/708/817/rrlyr?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/708/817/rrlyr?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/708/817/rrlyr?GETtext/xml+votable180.050000true10.701812540.842252780.0055555555555555566/2622 26233.322582951404819e-19 5.042107639525881e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/708/817?format=asciiOpticaldefaultJ/ApJ/708/817/table4Time-series magnitudes for RR Lyrae variablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFld[F1/F2] F1 or F2 field (1)meta.notecharSeqVariable identification (<[FMT2010] F1 NN> or <[FMT2010] F2 NN> in Simbad)meta.idintJD-BJulian Date of F435W observationdtime.epochdoubleF435WHST/ACS F435W filter VEGAMAG magnitudemagphot.mag;em.opt.Bfloate_F435WPhotometric uncertainty in F435Wmagstat.errorfloatBmagEquivalent Johnson-Cousins B band magnitudemagphot.mag;em.opt.BfloatJD-VJulian Date of F555W observationdtime.epochdoubleF555WHST/ACS F555W filter VEGAMAG magnitudemagphot.mag;em.opt.Vfloate_F555WPhotometric uncertainty in F555Wmagstat.errorfloatVmagEquivalent Johnson-Cousins V band magnitudemagphot.mag;em.opt.VfloatJ/ApJ/708/817/rrlyrRR Lyrae properties of Field 1 and Field 2PerPerioddtime.periodfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFldSimbad column added by the CDSobs.fieldcharSeqStar number (<[FMT2010] F1 NN> in table 2 or <[FMT2010] F2 NN> in table 3 in Simbad)meta.id;meta.mainintRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainH[1/4] Order of the Fourier series used to obtain the best fitstat.fit.paramintF435WHST/ACS F435W magnitude (B-band)magphot.mag;em.opt.BfloatF555WHST/ACS F555W magnitude (V-band)magphot.mag;em.opt.Vfloat<Vmag>Mean V-band magnitudemagphot.mag;em.opt.VfloatB-V<B>-<V> color indexmagphot.color;em.opt.B;em.opt.VfloatABExtinction in B-bandmagphys.absorption;em.opt.BfloatAVExtinction in V-bandmagphys.absorption;em.opt.VfloatresBRMS deviation of the data points from the fitting model, in B-bandmagstat.stdevfloatresVRMS deviation of the data points from the fitting model, in V-bandmagstat.stdevfloatType[RRc /RRab] RR-Lyrae type (RRc or RRab)meta.code;src.varcharLCLight curves of RR Lyrae starmeta.ref.urlcharSimbadSimbad column added by the CDScharEpochJulian date where each curve shows its maximum of light at phase {phi}=1dtime.epochdouble