J/ApJ/778/150ivo://CDS.VizieR/J/ApJ/778/150doi:10.26093/cds/vizier.17780150CDSSumi T.Bennett D.P.Bond I.A.Abe F.Botzler C.S.Fukui A.,Furusawa K.Itow Y.Ling C.H.Masuda K.Matsubara Y.Muraki Y.,Ohnishi K.Rattenbury N.Saito TO.Sullivan D.J.Suzuki D.,Sweatman W.L.Tristram P.J.Wada K.Yock P.C.M.(The MOA Collaboration)2018-01-30T07:18:08Z2015-06-08T14:43:48ZCDS support team

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

cds-question@unistra.frgravitational-lensingmilky-way-galaxysurveysWe present measurements of the microlensing optical depth and event rate toward the Galactic Bulge (GB) based on two years of the MOA-II survey. This sample contains ~1000 microlensing events, with an Einstein radius crossing time of t_E_<=200 days in 22 bulge fields covering ~42deg^2^ between -5{deg}<l<10{deg} and -7{deg}<b<-1{deg}. Our event rate and optical depth analysis uses 474 events with well-defined microlensing parameters. In the central fields with |l|<5{deg}, we find an event rate of {Gamma}=[2.39+/-1.1]e^[0.60+/-0.05](3-|b|)^x10^-5^/star/yr and an optical depth (for events with t_E_<=200days) of {tau}_200_=[2.35+/-0.18]e^[0.51+/-0.07](3-|b|)^x10^-6^ for the 427 events, using all sources brighter than I_s_<=20mag. The distribution of observed fields is centered at (l,b)=(0.{deg}38, -3.{deg}72). We find that the event rate is maximized at low latitudes and a longitude of l{approx}1{deg}. For the 111 events in 3.2deg^2^ of the central GB at |b|<=3.{deg}0 and 0.{deg}0<=l<=2.{deg}0, centered at (l,b)=(0.{deg}97, -2.{deg}26), we find {Gamma}=4.57_-0.46_^+0.51^x10^-5^/star/yr and {tau}_200_=3.64_-0.45_^+0.51^x10^-6^. We also consider a red clump giant (RCG) star sample with I_s_<17.5, and we find that the event rate for the RCG sample is slightly lower than but consistent with the all-source event rate. The main difference is the lack of long duration events in the RCG sample due to a known selection effect. Our results are consistent with previous optical depth measurements, but they are somewhat lower than previous all-source measurements, and slightly higher than previous RCG optical depth measurements. This suggests that the previously observed difference in optical depth measurements between all-source and RCG samples may largely be due to statistical fluctuations. These event rate measurements toward the central GB are necessary to predict the microlensing event rate and to optimize the survey fields in future space missions such as Wide Field Infrared Space Telescope.2013ApJ...778..150Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/778/150CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJS/216/12 : OGLE-III GB microlensing events (Wyrzykowski+, 2015)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/ApJ/631/906 : MACHO Galactic Bulge microlensing events (Thomas+, 2005)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://www.massey.ac.nz/~iabond/moa/ : Microlensing Observations inhttp://ogle.astrouw.edu.pl/ogle4/ews/ews.html : OGLE-IV early warning systemhttp://wise-obs.tau.ac.il/~wingspan/ : WISE events by seasonshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/778/150https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/778/150http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/778/150https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/778/150https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/778/150http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/778/150GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/778/150/table4 (Microlensing events used in the optical depth and event rate measurements)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/778/150/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/778/150/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/778/150/table4?GETtext/xml+votable180.050000true266.29686667-33.648566670.005555555555555556Cone search capability for table J/ApJ/778/150/table2 (MOA-II subfields with Galactic coordinates, the numbers of source stars and events, and the mean timescale and efficiencies for the all-source sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/778/150/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/778/150/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/778/150/table2?GETtext/xml+votable180.050000true266.179792-33.6243690.005555555555555556Cone search capability for table J/ApJ/778/150/table7 (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/778/150/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/778/150/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/778/150/table7?GETtext/xml+votable180.050000true266.179792-33.6243690.005555555555555556Cone search capability for table J/ApJ/778/150/table3 (MOA-II subfields with Galactic coordinates, the numbers of source stars and events, and the mean timescale and efficiencies for the red clump giant (RCG) sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/778/150/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/778/150/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/778/150/table3?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/778/150?format=asciiOpticaldefaultJ/ApJ/778/150/table4Microlensing events used in the optical depth and event rate measurementsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDField-chip-ID identifiermeta.id;meta.maincharRAJ2000[17/18] Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000[21/35] Degree of Declination (J2000)pos.eq.dec;meta.mainNdat[1348/7736] Number of data pointsmeta.numberintt0Julian Date peak magnification; JD-24540000dtime.epochdoubletE[0.4/157.6] Einstein radius crossing timedtime.crossingfloate_tE[0.03/12] Uncertainty in tEdstat.errorfloatu0[0.0003/0.98] Impact parametersrc.impactParamdoublee_u0[0/0.3] Uncertainty in u0stat.errordoubleImag[14.8/20] Source I band magnitudemagphot.mag;em.opt.Rfloatchi2[0.4/2] The {chi}^2^/degree of freedomstat.fit.doffloatJ/ApJ/778/150/table2MOA-II subfields with Galactic coordinates, the numbers of source stars and events, and the mean timescale and efficiencies for the all-source samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldField-chip-subfield identifierobs.fieldcharprimaryGLON[-5.3/10.6] Galactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latN*[939/128758] Number of stars in the subfieldmeta.numberintNev[0/5] Number of events in the subfieldmeta.numberint<tE>[6.9/54.5] Mean Einstein time scale <t_E_>dtime.crossingfloat<DE>[0.1/0.6] Mean detection efficiency <{epsilon}>stat.paramdoubleNsf[26/629] Number of subfields used (1)meta.numberintNsfW[7.5/202.2] Number of weighted subfields used (2)meta.numberfloatN*MANumber of stars in subfields used (1)meta.numberintN*MAWNumber of weighted stars in subfields used (2)meta.numberintNevMA[2/118] Number of events in subfields used (1)meta.numberintNevMAW[0.1/39.5] Number of events in weighted subfields used (2)meta.numberfloat_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.decnullableindexedJ/ApJ/778/150/table7Average 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.recordintFieldField-chip-subfield identifierobs.fieldcharprimaryGLON[-5.3/10.6] Galactic longitudedegpos.galactic.lonGLATGalactic latitudedegpos.galactic.latNsf[26/115] Number of subfields used (1)meta.numberintN*[483811/10853361] Number of stars in subfields used (2)meta.numberintNev[2/118] Number of events in subfields used (2)meta.numberinttau[0.17/11.9] Microlensing optical depth {tau} (3)phys.absorption.opticalDepthdoubles_tau[0.09/5.8] The 68% symmetric error in taustat.errordoublee_tau[0.07/4.4] The 68% lower limit in taustat.errordoubleE_tau[0.1/7.2] The 68% upper limit in taustat.error;stat.maxdoubleGam[3/59.5] Event rate {Gamma} per star per 10^6^year1e-06yr**-1time;arith.ratiofloats_Gam[2/35.5] The 68% symmetric error in Gamma1e-06yr**-1stat.errorfloate_Gam[0.003/10] The 68% lower limit in Gamma1e-06yr**-1stat.errordoubleE_Gam[2.5/33.6] The 68% upper limit in Gamma1e-06yr**-1stat.error;stat.maxfloatGam.d[2.4/163.1] Event rate {Gamma}_deg2_ per square degree per yeardeg**-2.yr**-1time;arith.ratiodoubles_Gam.d[4.2/97.3] The 68% symmetric error in Gammaddeg**-2.yr**-1stat.errorfloate_Gam.d[0.7/99.2] The 68% lower limit in Gammaddeg**-2.yr**-1stat.errordoubleE_Gam.d[5.6/42.2] The 68% upper limit 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.decnullableindexedJ/ApJ/778/150/table3MOA-II subfields with Galactic coordinates, the numbers of source stars and events, and the mean timescale and efficiencies for the red clump giant (RCG) sampleGLATGalactic latitudedegpos.galactic.latrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFieldField-chip-subfield identifierobs.fieldcharprimaryGLON[-5.3/10.6] Galactic longitudedegpos.galactic.lonN*[939/128758] Number of stars in the subfieldmeta.numberintNev[0/5] Number of events in the subfieldmeta.numberint<tE>[6.9/54.5] Mean Einstein time scale <t_E_>dtime.crossingfloat<DE>[0.1/0.6] Mean detection efficiency <{epsilon}>stat.paramdoubleNsf[26/629] Number of subfields used (1)meta.numberintNsfW[7.5/202.2] Number of weighted subfields used (2)meta.numberfloatN*MANumber of stars in subfields used (1)meta.numberintN*MAWNumber of weighted stars in subfields used (2)meta.numberintNevMA[2/118] Number of events in subfields used (1)meta.numberintNevMAW[0.1/39.5] Number of events in weighted subfields used (2)meta.numberfloat_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