J/ApJ/827/139ivo://CDS.VizieR/J/ApJ/827/139doi:10.26093/cds/vizier.18270139CDSSumi T.Penny M.T.2017-02-10T12:58:33Z2017-01-04T14:08:05ZCDS support team

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

cds-question@unistra.frmilky-way-galaxygravitational-lensingsurveysWe find that significant incompleteness in stellar number counts results in a significant overestimate of the microlensing optical depth {tau} and event rate per star per year {Gamma} toward the Galactic bulge from the first two years of the MOA-II survey. We find that the completeness in red clump giant (RCG) counts f_RC_ decreases proportional to the galactic latitude b, as f_RC_=(0.63+/-0.11)-(0.052+/-0.028)xb, ranging between 1 and 0.7 at b=-6{deg}~-1.5{deg}. The previous measurements using all sources by difference image analysis (DIA) by MACHO and MOA-I suffer the same bias. On the other hand, the measurements using an RCG sample by OGLE-II, MACHO, and EROS were free from this bias because they selected only the events associated with the resolved stars. Thus, the incompleteness both in the number of events and stellar number count cancel out. We estimate {tau} and {Gamma} by correcting this incompleteness. In the central fields with |l|<5{deg}, we find {Gamma}=[18.74+/-0.91]x10^-6^exp[(0.53+/-0.05)(3-|b|)]/star/yr and {tau}_200_=[1.84+/-0.14]x10^-6^exp[(0.44+/-0.07)(3-|b|)] for the 427 events with t_E_<=200 days using all sources brighter than I_s_<=20mag. Our revised all-source {tau} measurements are about 2{sigma} smaller than the other all-source measurements and are consistent with the RCG measurements within 1{sigma}. We conclude that the long-standing problem on discrepancy between the high {tau} with all-source samples by DIA and low {tau} with RCG samples can probably be explained by the incompleteness of the stellar number count. A model fit to these measurements predicts {Gamma}=4.60+/-0.25x10^-5^/star/yr at |b|~-1.4{deg} and -2.25{deg}<l<3.75{deg} for sources with I<=20, where the future space mission, Wide Field Infrared Space Telescope, will observe.2016ApJ...827..139Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/827/139CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/778/150 : Microlensing events toward the Bulge from MOA-II (Sumi+, 2013)J/A+A/549/A147 : Abundances of microlensed Bulge stars. V. (Bensby+, 2013)J/ApJ/711/L48 : 2008 OGLE Bulge microlensing alerts (Cohen+, 2010)J/A+A/454/185 : EROS-2 microlensing parameters (Hamadache+, 2006)J/ApJ/636/240 : OGLE II microlensing parameters (Sumi+, 2006)J/AcA/52/217 : OGLE II. VI photometry of Galactic Bulge (Udalski+, 2002)J/AcA/51/175 : OGLE-II DIA microlensing events (Wozniak+, 2001)J/AcA/50/1 : OGLE microlensing events in Galactic Bulge (Udalski+, 2000)http://ogle.astrouw.edu.pl/ogle4/ews/ews.html : OGLE-IV early warning systemhttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/827/139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/827/139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/827/139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/827/139https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/827/139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/827/139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/827/139/table4 (Average microlensing optical depth and event rates at the position of each subfield for the all-source sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/827/139/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/827/139/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/827/139/table4?GETtext/xml+votable180.050000true266.179792-33.6243690.0055555555555555565/7179 7181 7182 7183 7194 7195 7205 7216 7217 7220 7221 7266 6/28703 28709 28710 28711 28715 28721 28722 28723 28768 28770 28771 28774 28775 28792 28794 28795 28798 28799 28804 28816 28817 28819 28829 28872 28873 28876 28877 28888 28889 28893 29056 29058 29059 29068 29070https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/827/139?format=asciidefaultJ/ApJ/827/139/table4Average microlensing optical depth and event rates at the position of each subfield for the all-source samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldThe field-chip-subfield identifierobs.fieldcharGLONGalactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latNsub[26/115] Number of subfields (1)meta.numberintNstarNumber of stars in subfields (2)meta.numberintNev[2/118] Number of events in subsfields (2)meta.numberinttau[0.1/8.6] Microlensing optical depth in 1e-6 (3)phys.absorption.opticalDepthdoubles_tau[0.09/4.2] The 68% symmetric error in taustat.errordoublee_tauLower 68% error in taustat.errordoubleE_tauUpper 68% error in taustat.error;stat.maxdoubleGamma[2/43] Event rate per star per year in 1e-61e-06yr**-1time;arith.ratiofloats_Gamma[1/26] The 68% symmetric error in Gamma1e-06yr**-1stat.errorfloate_GammaLower 68% error in Gamma1e-06yr**-1stat.errorfloatE_GammaUpper 68% error in Gamma1e-06yr**-1stat.error;stat.maxfloatGammad[2/164] Event rate per square degree per yeardeg**-2.yr**-1time;arith.ratiodoubles_Gammad[4/98] The 68% symmetric error in Gammaddeg**-2.yr**-1stat.errorfloate_GammadLower 68% error in Gammaddeg**-2.yr**-1stat.errordoubleE_GammadUpper 68% error in Gammaddeg**-2.yr**-1stat.error;stat.maxfloat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)degpos.eq.decnullableindexed