J/A+A/689/A240ivo://CDS.VizieR/J/A+A/689/A240doi:10.26093/cds/vizier.36890240CDSZoccali M.Quezada C.Contreras Ramos R.Valenti E.,Valenzuela-Navarro A.Olivares Carvajal J.Rojas Arriagada A.,Minniti J.H.Gran F.De Leo M.2025-07-04T20:02:09Z2024-09-17T12:24:12ZCDS support team

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

cds-question@unistra.frhorizontal-branch-starsvariable-starsinfrared-photometryphotometryclassificationObservational evidence has accumulated in recent years, showing that the Galactic bulge includes two populations, a metal-poor one and a metal-rich one, which in addition to having different metallicities show different alpha over iron abundances, spatial distribution, and kinematics. While the metal-rich, barred component has been fairly well characterized, the metal-poor, spheroidal component has been more elusive and harder to describe. RR Lyrae variables are clean tracers of the old bulge component, and they are, on average, more metal-poor than red clump stars. In the present paper, we provide a new catalog of 16488 ab-type RR Lyrae variables in the bulge region within |l|<10 and |b|<2.8, extracted from multi-epoch Point Spread Function photometry performed on VISTA Variable in the Via Lactea survey data. We used the catalog to constrain the shape of the old, metal-poor, bulge stellar population. The identification of ab-type RR Lyrae among a large sample of candidate variables of different types has been performed via a combination of a Random Forest classifier and visual inspection. We optimized this process in such a way to extract a clean catalog with high purity, although for this reason its completeness, close to the midplane, is lower compared to a few other near-infrared catalogs covering the same region of the sky. We used the present catalog to derive the shape of their distribution around the Galactic center, resulting in an elongated spheroid with projected axis ratio of b/a~0.7 and an inclination angle of {phi}~20 degrees. We discuss how observational biases, such as errors on the distances and a nonuniform sampling in longitude, affect both the present measurements and previous ones, especially those based on red clump stars. Because the latter have not been taken into account before, we refrain from a quantitative comparison between these shape parameters and those derived for the main Galactic bar. Nonetheless, qualitatively, taking into account observational biases would lower the estimated ellipticity of the bar derived from red clump stars, and hence reduce the difference with the present results. We publish a high-purity RRab sample for future studies of the oldest Galactic bulge population, close to the midplane. We explore different choices for the period-luminosity-metallicity relation, highlighting how some of them introduce spurious trends of distance with either the period or the metallicity, or both. We provide evidence that they trace a structure that is less elongated than the main bar, though we also highlight some biases of these kind of studies not discussed before.2024A&A...689A.240Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/689/A240CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/376 : VISTA Variable in the Via Lactea Survey (VVV) DR4.2J/AcA/69/321 : OGLE RR Lyrae stars in Galactic bulge & disk (Soszynski+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/689/A240https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/689/A240http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/689/A240https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/689/A240https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/689/A240http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/689/A240GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/689/A240/table3 (Catalog of ab-type RR Lyrae within |l|<10 and |b|<2.8 (catalog)))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/689/A240/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/689/A240/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/689/A240/table3?GETtext/xml+votable180.050000true262.14215-38.378110.0055555555555555564/1800-1801 1806-1807 2653 5/7208-7209 7212-7213 7216 7218-7219 7222-7223 7272 10620-10621 6/28714-28715 28718-28719 28730 28845 28856-28857 28860-28861 28870-28871 28882-28883 29064 29066-29067 29096-29098 29265 29268-29269 29440 42362-42363 42366-42367 42439 42445 42447 42468-42469 424717.952274030004205e-20 1.7798557115773645e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/689/A240?format=asciiInfrareddefaultJ/A+A/689/A240/table3Catalog of ab-type RR Lyrae within |l|<10 and |b|<2.8 (catalog))IDStar ID (bNNN_NNN_NNNNN)meta.id;meta.maincharprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGLON[] Galactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latdoubleKmagK band magnitudemagphot.mag;em.IR.Kfloate_KmagError in K band magnitudemagstat.error;phot.magfloatJmag? J band magnitudemagphot.mag;em.IR.Jfloatnullablee_Jmag? Error in J band magnitudemagstat.error;phot.magfloatnullable[Fe/H]Metallicity in dexphys.abund.Zdoublee_[Fe/H]Error in metallicitystat.error;phys.abund.FefloatE(J-K)? Reddening measured from intrinsic colormagphot.color.excessfloatnullablee_E(J-K)? Error in reddeningmagstat.errorfloatnullableAmpAmplitude in magnitudemagphot.magdoubleSNRSignal-to-noise ratiostat.snrdoublePerPerioddtime.perioddoubleDist? Distancekpcpos.distancefloatnullablee_Dist? Error in distancekpcstat.errorfloatnullableX? X coordinate in Cartesian systemkpcpos.cartesian.x;pos.galacticfloatnullableY? Y coordinate in Cartesian systemkpcpos.cartesian.y;pos.galacticfloatnullableZ? Z coordinate in Cartesian systemkpcpos.cartesian.z;pos.galacticfloatnullableRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainindexedDEJ2000Declination (J2000)degpos.eq.dec;meta.mainindexedMoreindicates features in tables features and postfeatmeta.ref.urlcharFlagStar origin catalog (OGLE or VVV)meta.code.errorcharLCShow the light curvemeta.ref.urlcharSimbadNameSimbad column added by the CDSmeta.idcharnullableJ/A+A/689/A240/featuresFeatures used by the Random Forest classifierrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPer2Second perioddtime.perioddoubleA1/A2Ratio of two amplitudesphot.mag;arith.ratiofloatACstdStandard deviation of the light curve's auto-convolutionstat.stdevfloatADAnderson-Darling test resultsrc.var.amplitudefloatBeyond1StdPercentage of points beyond one standard deviation from the weighted meanmeta.numberfloatGPDownRatioTime of descent in phase (Gaussian process)stat.fit.paramfloatGPRDRatioRise to descent ratiostat.fit.paramfloatGPRiseRatioRising time ratiostat.fit.paramfloatGPSkewSkewness of the light curve (Gaussian process)stat.fit.paramfloatRcsRatio between MAD and Sigmastat.fit.paramfloatTmRatio between minimum-mean difference and total amplitudestat.fit.paramfloatA0Amplitude of the Fourier harmonic 0src.var.amplitudefloatA1Amplitude of the Fourier harmonic 1src.var.amplitudefloatA2Amplitude of the Fourier harmonic 2src.var.amplitudefloatA3Amplitude of the Fourier harmonic 3src.var.amplitudefloatA4Amplitude of the Fourier harmonic 4src.var.amplitudefloatA5Amplitude of the Fourier harmonic 5src.var.amplitudefloatA6Amplitude of the Fourier harmonic 6src.var.amplitudefloatA7Amplitude of the Fourier harmonic 7src.var.amplitudefloatAmpAmplitude of the light curvemagphot.magfloatkurtosisKurtosis of the magnitude distributionstat.fit.paramfloatmadMean absolute deviationstat.stdevfloatmedianaMedian value of the light curvemeta.notefloatmpr20Ratio between magnitude at 60th and 40th percentilestat.fit.omcfloatmpr35Ratio between magnitude at 67th and 32nd percentilestat.fit.omcfloatmpr50Ratio between magnitude at 75th and 25th percentilestat.fit.omcfloatmpr65Ratio between magnitude at 82nd and 17th percentilestat.fit.omcfloatmpr80Ratio between magnitude at 90th and 10th percentilestat.fit.omcfloatmvRatio between Sigma and median magnitudestat.fit.omcfloatphi1Phase shift of Fourier harmonic 1stat.fit.paramdoublephi2Phase shift of Fourier harmonic 2stat.fit.paramdoublephi3Phase shift of Fourier harmonic 3stat.fit.paramdoublephi4Phase shift of Fourier harmonic 4stat.fit.paramdoublephi5Phase shift of Fourier harmonic 5stat.fit.paramdoublephi6Phase shift of Fourier harmonic 6stat.fit.paramdoublephi7Phase shift of Fourier harmonic 7stat.fit.paramdoublesigmaStandard deviation of magnitudesstat.stdevfloatskewnessSkewness of magnitude distributionstat.fit.paramfloatslopeSlope of linear fit to light curvearith.grad;pos.distance;stat.fit.paramfloatA21Amplitude ratio (A2/A1)phot.mag;arith.ratiofloatA31Amplitude ratio (A3/A1)src.var.amplitude;arith.ratiofloatA41Amplitude ratio (A4/A1)src.var.amplitude;arith.ratiofloatP21Phase shift ratio (phi2/phi1)stat.fit.paramfloatP31Phase shift ratio (phi3/phi1)stat.fit.paramfloatP41Phase shift ratio (phi4/phi1)stat.fit.paramfloatIDStar ID (bNNN_NNN_NNNNN)meta.id;meta.maincharFlagStar origin catalog (VVV)meta.code.errorcharJ/A+A/689/A240/postfeatPost-Random-Forest classification featuresrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPer2Second perioddtime.perioddoublepostmseRRabMean square error of the RRab template fitstat.stdevfloatpostmseRRcMean square error of the RRc template fitstat.stdevfloatpostGPmseMean square error of the Gaussian Processstat.stdevfloatpostsigmaStandard deviationstat.stdevfloatpostrhoCorrelation coefficientstat.fit.paramfloatpostGPRiseRatioRatio of rise time in phasestat.fit.paramfloatpostGPDownRatioRatio of descent time in phasestat.fit.paramfloatpostGPRDRatioRatio of rise over descent time in phasestat.fit.paramfloatpostGPSkewSkewnessstat.fit.paramfloatpostSNratioSignal-to-noise ratiostat.snrfloatpostNpeaksNumber of peaksmeta.numberintpostaliasscoreAlias scoremeta.codeintpostNpointsNumber of epochsmeta.numberintIDStar ID (bNNN_NNN_NNNNN)meta.id;meta.maincharFlagStar origin catalog (VVV)meta.code.errorchar