J/ApJ/736/133ivo://CDS.VizieR/J/ApJ/736/133doi:10.26093/cds/vizier.17360133CDSAn D.Ramirez S.V.Sellgren K.Arendt R.G.Boogert A.C.A.,Robitaille T.P.Schultheis M.Cotera A.S.Smith H.A.Stolovy S.R.2017-06-26T11:50:18Z2013-01-28T13:37:55ZCDS support team

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

cds-question@unistra.frinfrared-photometrychemical-abundancesspectroscopyextinctionyoung-stellar-objectsWe present results from our spectroscopic study, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic center (GC). Our sample of 107 YSO candidates was selected based on Infrared Array Camera (IRAC) colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone, which spans the central ~300pc region of the Milky Way. We obtained IRS spectra over 5-35um using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4um shoulder on the absorption profile of 15um CO_2_ ice, suggestive of CO_2_ ice mixed with CH_3_OH ice on grains. This 15.4um shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that nine massive YSOs also reveal molecular gas-phase absorption from CO_2_, C_2_H_2_, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8-23M_{sun}_, which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of ~0.07M_{sun}/yr at the GC.2011ApJ...736..133Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/736/133CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008)II/295 : Spitzer IRAC survey of the galactic center (Ramirez+, 2008)J/A+A/530/A72 : Fermi sources with massive YSO associations (Munar-Adrover+,J/ApJ/702/178 : YSOs in the central 400pc of the Galaxy (Yusef-Zadeh+, 2009)J/ApJ/697/1741 : Warped disks of YSOs in Galactic center (Bartko+, 2009)J/A+A/495/157 : Interstellar extinction in Galactic Center (Schultheis+, 2009)J/ApJS/175/277 : Submillimeter-Continuum SCUBA detections (Di Francesco+, 2008)J/ApJS/174/481 : 2LC Compact Radio Sources in the GC (Lazio+, 2008)J/A+A/453/535 : Classification of bright mid-IR sources (Schuller+, 2006)J/AJ/130/586 : Compact radio sources in the galactic plane (White+, 2005)J/ApJS/155/421 : Survey of Galactic Center region at 20cm (Yusef-Zadeh+, 2004)J/A+A/392/971 : Catalogue of bright YSO candidates in ISOGAL (Felli+, 2002)J/ApJS/118/201 : Galactic Center 6 and 20cm survey (Lazio+, 1998)J/ApJS/91/347 : A 5-GHz VLA Survey of the Galactic Plane (Becker+ 1994)J/ApJS/74/181 : Small-diameter radiosources catalogue (Zoonematkermani+, 1990)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/736/133https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/736/133http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/736/133https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/736/133https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/736/133http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/736/133GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/736/133/table1 (Infrared Spectrograph (IRS) sample of candidate YSOs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/736/133/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/736/133/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/736/133/table1?GETtext/xml+votable180.050000true265.949875-29.64477780.0055555555555555566/28825 28827 28830 288312.232294361788794e-22 1.692669228152603e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/736/133?format=asciiOpticalInfrareddefaultJ/ApJ/736/133/table1Infrared Spectrograph (IRS) sample of candidate YSOsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSSTGC[244532/817663] Source identificationmeta.codeintprimaryYSimbad column added by the CDSmeta.ref.urlcharRAJ2000[17] Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000[28/29] Degree of declination (J2000)pos.eq.dec;meta.mainDateObservation date (2008/May or 2008/Oct)time.epoch;obsnullableUs[yes/maybe/no ] This work YSO status ("yes"=YSO, "maybe"=possible YSO)meta.codecharF02[yes/no ] Felli et al. (2002, Cat. J/A+A/392/971) YSO statusmeta.codecharS06[yes/no ] Schuller et al. (2006, Cat. J/A+A/453/535) YSO statusmeta.codecharY09[yes/no ] Yusef-Zadeh et al. (2009, Cat. J/ApJ/702/178) YSO statusmeta.codecharf_Y09[b] b: 4.5um excess source without a 24um counterpartmeta.codecharYSOcatCross-match within 2.5" with the YSO catalogs: J/A+A/392/971, J/A+A/453/535 and J/ApJ/702/178meta.ref.urlintnullableJ/ApJ/736/133/YSOsYSOs and possible YSOs: data reduction, absorption A_V_, photometric properties, SED fitting and mass estimatesl_F450Limit flag on F450meta.code.errorcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSSTGC[300758/817663] Source identificationmeta.id;meta.mainintModBaseline IRS module (LL2 or SL1) (1)instr.baselinecharSL1? SL1 flux scaling factor (2)arith.factorfloatnullablee_SL1? Uncertainty on SL1stat.errorfloatnullableSL2? SL2 flux scaling factor (2)arith.factorfloatnullablee_SL2? Uncertainty on SL2stat.errorfloatnullableSL3? SL3 flux scaling factor (2)arith.factorfloatnullablee_SL3? Uncertainty on SL3stat.errorfloatnullableLL1? LL1 flux scaling factor (2)arith.factorfloatnullablee_LL1? Uncertainty on LL1stat.errorfloatnullableLL2? LL2 flux scaling factor (2)arith.factorfloatnullablee_LL2? Uncertainty on LL2stat.errorfloatnullableSetExcluded data set (3)meta.notecharAvL[17.6/76.5]? Dust extinction with low-resolution modules (SL+LL)magphys.absorptionfloatnullablee_AvL? Uncertainty on AvLmagstat.errorfloatnullableAvH[19.9/64.5] Dust extinction with high-resolution modules (SH+LH)magphys.absorptionfloate_AvHUncertainty on AvHmagstat.errorfloatAv0[19/76] Foreground extinction (1)magphys.absorptioninte_Av0Uncertainty on Avmagstat.errorintJmag[15.33/19.06]? UKIDSS J-band magnitude (1)magphot.mag;em.IR.Jfloatnullablee_Jmag? Uncertainty on Jmagmagstat.error;phot.mag;em.IR.JfloatnullableHmag? UKIDSS H-band magnitude (1)magphot.mag;em.IR.Hfloatnullablee_Hmag? Uncertainty on Hmagmagstat.error;phot.mag;em.IR.HfloatnullableKmag[10.98/16.88]? UKIDSS K-band magnitude (1)magphot.mag;em.IR.Kfloatnullablee_Kmag? Uncertainty on Kmagmagstat.error;phot.mag;em.IR.Kfloatnullable[3.6]? 3.6um IRAC band magnitude (2)magphot.mag;em.IR.3-4umfloatnullable[4.5]? 4.5um IRAC band magnitude (2)magphot.mag;em.IR.4-8umfloatnullable[5.8]? 5.8um IRAC band magnitude (2)magphot.flux.density;em.IR.4-8umfloatnullable[8.0][4.8/8.9]? 8.0um IRAC band magnitude (2)magphot.flux.density;em.IR.8-15umfloatnullable[24][-1.1/3.3]? 24um synthetic magnitude (3)magphot.flux.density;em.IR.15-30umfloatnullableF450[1.9/7214.4]? SCUBA 450um flux (4)Jyphot.flux.density;em.mm.400-750GHzfloatnullablee_F450? Uncertainty on F450Jystat.errorfloatnullableF850[0.1/326.2]? SCUBA 850um flux (4)Jyphot.flux.density;em.mm.200-400GHzfloatnullablee_F850? Uncertainty on F850Jystat.errorfloatnullablelogM[0.88/1.42] Log of masslog(solMass)phys.massfloate_logM? Uncertainty on logMlog(solMass)stat.errorfloatnullablelogL[2.94/4.97] Log of total luminositylog(solLum)phys.luminosityfloate_logL? Uncertainty on logLlog(solLum)stat.errorfloatnullableAv[20/40] ISM extinctionmagphys.absorptionfloate_Av? Uncertainty on Avmagstat.errorfloatnullablelogdM/dt[-4.19/-2.24]? Envelope accretion ratelog(solMass.yr**-1)phys.mass.lossfloatnullablee_logdM/dt? Uncertainty on logdM/dtlog(solMass.yr**-1)stat.errorfloatnullablelogAge[3.19/6.17] Agelog(yr)time.agefloate_logAge? Uncertainty on logAgelog(yr)stat.error;time.agefloatnullablelogMrad[1.18/1.39]? Radio modeling masslog(solMass)phys.massfloatnullabler_logMrad[1/8]? logMrad reference (1)meta.ref;pos.frameintnullableJ/ApJ/736/133/table3CO_2_ ice decomposition for YSOs and possible YSOsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSSTGC[300758/817663] Source identificationmeta.id;meta.mainint[Npol][17.06/18.31] Log of gas-phase column density (N_col_) polarlog(cm**-2)phys.columnDensityfloate_[Npol]Uncertainty on [Npol]log(cm**-2)stat.errorfloatl_[Napol]Limit flag on [Napol]meta.code.errorchar[Napol][16.79/18.03] Log of N_col_ apolarlog(cm**-2)phys.columnDensityfloate_[Napol]? Uncertainty on [Napol]log(cm**-2)stat.errorfloatnullablel_[Nsh]Limit flag on [Nsh]meta.code.errorchar[Nsh][16.65/17.57] Log of N_col_ shoulderlog(cm**-2)phys.columnDensityfloate_[Nsh]? Uncertainty on [Nsh]log(cm**-2)stat.errorfloatnullablel_[Nd]Limit flag on [Nd]meta.code.errorchar[Nd][16.17/16.82] Log of N_col_ dilutedlog(cm**-2)phys.columnDensityfloate_[Nd]? Uncertainty on [Nd]log(cm**-2)stat.errorfloatnullablel_[Np]Limit flag on [Np]meta.code.errorchar[Np][16.78/17.41] Log of N_col_ purelog(cm**-2)phys.columnDensityfloate_[Np]? Uncertainty on [Np]log(cm**-2)stat.errorfloatnullable[Nt][17.38/18.54] Log of N_col_ totallog(cm**-2)phys.columnDensityfloate_[Nt]Uncertainty on [Nt]log(cm**-2)stat.errorfloatChi2[99/2347] Total chi-square of the fitstat.fit.param;meta.modelledintNtot[118/152] Number of data points used in the fitmeta.numberintStatusYSO status ("yes", "maybe" or "known stars")meta.codecharJ/ApJ/736/133/table4Gas-phase absorption features of YSOs and possible YSOsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSSTGC[524665/803471] Source identificationmeta.id;meta.mainintTexC2[100/400]? C_2_H_2_ excitation temperatureKphys.atmol.excitationintnullablee_TexC2? Uncertainty on TexC2Kstat.errorintnullable[C2H2][15.7/16.9]? Log of C_2_H_2_ column densitylog(cm**-2)phys.columnDensityfloatnullablee_[C2H2]? Uncertainty on [C2H2]log(cm**-2)stat.errorfloatnullableC2H2[-6.9/-5.4]? C_2_H_2_ abundance/H_2_ (1)phys.abundfloatnullablee_C2H2? Uncertainty on C2H2stat.errorfloatnullableTexH[100/400]? HCN excitation temperatureKphys.atmol.excitationintnullablee_TexH? Uncertainty on TexHKstat.errorintnullablef_TexH[b] 2 possible values for SSTGC 803187 (2)meta.codechar[HCN][16.4/17]? Log of HCN column densitylog(cm**-2)phys.columnDensityfloatnullablee_[HCN]? Uncertainty on [HCN]log(cm**-2)stat.errorfloatnullablef_[HCN][b] 2 possible values for SSTGC 803187 (2)meta.codecharHCN[-6.4/-5.3]? HCN abundance/H_2_ (1)phys.abundfloatnullablee_HCN? Uncertainty on HCNstat.errorfloatnullableTex[100/200] CO_2_ excitation temperatureKphys.atmol.excitationinte_TexUncertainty on TexKstat.errorint[CO2][16.2/17.2] Log of CO_2_ column densitylog(cm**-2)phys.columnDensityfloate_[CO2]? Uncertainty on [CO2]log(cm**-2)stat.errorfloatnullableCO2[-6.4/-5.1]? CO_2_ abundance/H_2_ (1)phys.abundfloatnullablee_CO2? Uncertainty on CO2stat.errorfloatnullableCO2g[0.02/0.15] CO_2_ gas to solid ratiostat.fit.omcfloate_CO2gUncertainty on CO2gstat.errorfloat