J/AJ/144/113ivo://CDS.VizieR/J/AJ/144/113doi:10.26093/cds/vizier.51440113CDSChavez J.M.Macri L.M.Pellerin A.2017-10-11T05:13:44Z2013-10-30T10:27:01ZCDS support team

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

cds-question@unistra.frgalaxiesvariable-starshst-photometryinfrared-photometryvisible-astronomyphotometryA precise and accurate determination of the Hubble constant based on Cepheid variables requires proper characterization of many sources of systematic error. One of these is stellar blending, which biases the measured fluxes of Cepheids and the resulting distance estimates. We study the blending of 149 Cepheid variables in M33 by matching archival Hubble Space Telescope data with images obtained at the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5m telescope, which differ by a factor of 10 in angular resolution. We find that 55%+/-4% of the Cepheids have no detectable nearby companions that could bias the WIYN V-band photometry, while the fraction of Cepheids affected below the 10% level is 73%+/-4%. The corresponding values for the I band are 60%+/-4% and 72%+/-4%, respectively. We find no statistically significant difference in blending statistics as a function of period or surface brightness. Additionally, we report all the detected companions within 2" of the Cepheids (equivalent to 9pc at the distance of M33) which may be used to derive empirical blending corrections for Cepheids at larger distances.2012AJ....144..113Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/144/113CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/193/26 : The M33 synoptic stellar survey. I. (Pellerin+, 2011)J/ApJ/730/119 : HST/WFC3 observations of Cepheids in SN Ia hostsJ/ApJ/699/839 : Newly identified M33 star clusters. II. (San Roman+, 2009)J/AJ/134/2168 : BVI photometry of M33 star clusters (Park+, 2007)J/ApJ/652/1133 : BVI photometry of NGC 4258 Cepheids (Macri+, 2006)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/MNRAS/371/1405 : Variables in M33 (Hartman+, 2006)J/ApJ/652/313 : BV phot. of a detached EB in M33 (Bonanos+, 2006)J/AJ/132/1361 : RR Lyrae variables in M33 (Sarajedini+, 2006)J/AJ/121/870 : BVI photometry of Variables in M33 (Macri+, 2001)J/AJ/121/861 : BVI photometry of central part of M33 (Macri+, 2001)J/AJ/122/2477 : DIRECT variables in M33B field (Mochejska+, 2001)J/AJ/121/2032 : Direct variables in M33A field (Mochejska+, 2001)J/A+A/366/498 : VI photometry of M33 star clusters (Chandar+, 2001)J/ApJS/122/431 : Star Clusters in M33 (Chandar+, 1999)J/AJ/110/1649 : HST VI photometry near the M33 nucleus (Mighell+ 1995)J/AJ/110/2715 : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/144/113https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/144/113http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/144/113https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/144/113https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/144/113http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/144/113GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/144/113/table2 (Cepheid properties)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/144/113/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/144/113/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/144/113/table2?GETtext/xml+votable180.050000true23.384833330.47216670.0055555555555555566/2154 21552.0401237512456292e-19 2.706461185444514e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/144/113?format=asciiOpticalInfrareddefaultJ/AJ/144/113/table2Cepheid propertiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[M33SSS]Cepheid identifier (G1)meta.id;meta.maincharprimaryNcNumber of companions for this Cepheid (table3)meta.numberintnullablePerPeriod of Cepheiddtime.periodfloatVmagV-band (HST F555W or F606W) magnitude of Cepheidmagphot.mag;em.opt.Vfloate_VmagUncertainty in Vmagmagstat.error;phot.mag;em.opt.VfloatSV[0/1.2] V-band blending level (G2)stat.fit.paramfloate_SVUncertainty in SVstat.errorfloatImagI-band (HST F814W) magnitude of Cepheidmagphot.mag;em.opt.Ifloate_ImagUncertainty in Imagmagstat.error;phot.mag;em.opt.IfloatSI[0/0.9] I-band blending level (G2)stat.fit.paramfloate_SIUncertainty in SIstat.errorfloatmuVV-band background surface brightnessmag.arcsec**-2phot.mag.sb;em.opt.VfloatmuII-band background surface brightnessmag.arcsec**-2phot.mag.sb;em.opt.IfloatHSTField designation (for HST image) where Cepheid is locatedobs.fieldcharWIYNField designation (for WIYN image) where Cepheid is located (G1)obs.fieldcharPM11Display the photometric data from the M33 Synoptic Stellar Survey (Pellerin & Macri, 2011, cat. J/ApJS/193/26)meta.ref.urlcharSimbadSimbad column added by the CDSmeta.refchar_RAPositions from SIMBAD database (right ascension part)degpos.eq.ra;meta.main_DEPositions from SIMBAD database (declination part)degpos.eq.dec;meta.mainJ/AJ/144/113/table3Stars found within 2" of Cepheid variables[M33SSS]Cepheid identifier (G1)meta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintcID[1/428] Companion IDmeta.code.multipintSepxx-axis separation from Cepheidarcsecpos.angDistancefloatSepyy-axis separation from Cepheidarcsecpos.angDistancefloatSepr[0.04/2.08] radial separation from Cepheidarcsecpos.angDistancefloatVmag? V-band (HST F555W or HST F606W) magnitude of starmagphot.mag;em.opt.Vfloatnullablee_Vmag? Uncertainty in Vmagmagstat.error;phot.mag;em.opt.VfloatnullableImag? I-band (HST F814W) magnitude of starmagphot.mag;em.opt.Ifloatnullablee_Imag? Uncertainty in Imagmagstat.error;phot.mag;em.opt.Ifloatnullable