J/ApJ/930/16ivo://CDS.VizieR/J/ApJ/930/16doi:10.26093/cds/vizier.19300016CDSJang D.An D.Sellgren K.Ramirez S.V.Boogert A.C.A.Schultheis M.2026-02-10T20:05:24Z2024-04-29T08:50:57ZCDS support team

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

cds-question@unistra.frgalactic-centeryoung-stellar-objectsinfrared-astronomyspectroscopystellar-spectral-typesextinctionTo study the demographics of interstellar ices in the Central Molecular Zone (CMZ) of the Milky Way, we obtain near-infrared spectra of 109 red point sources using NASA IRTF/SpeX at Maunakea. We select the sample from near- and mid-infrared photometry, including 12 objects in the previous paper of this series, to ensure that these sources trace a large amount of absorption through clouds in each line of sight. We find that most of the sample (100 objects) show CO band-head absorption at 2.3{mu}m, tagging them as red (super-) giants. Despite the photospheric signature, however, a fraction of the sample with L-band spectra (9/82=0.11) exhibit large H_2_O ice column densities (N>2x10^18^cm^-2^), and six of them also reveal CH_3_OH ice absorption. As one of such objects is identified as a young stellar object (YSO) in our previous work, these ice-rich sight lines are likely associated with background stars in projection to an extended envelope of a YSO or a dense cloud core. The low frequency of such objects in the early stage of stellar evolution implies a low star-formation rate (<~0.02M_{sun}_/yr), reinforcing the previous claim on the suppressed star-formation activity in the CMZ. Our data also indicate that the strong "shoulder" CO_2_ ice absorption at 15.4{mu}m observed in YSO candidates in the previous paper arises from CH3OH-rich ice grains having a large CO2 concentration [N(CO_2_)/N(CH_3_OH)~1/3].2022ApJ...930...16Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/930/16CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)II/295 : Spitzer IRAC survey of the galactic center (Ramirez+, 2008)II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)I/350 : Gaia EDR3 (Gaia Collaboration, 2020)VIII/96 : 6-GHz methanol multibeam maser catalogue (Caswell+, 2010-12)VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/ApJS/86/713 : IR spectroscopy of ices (Hudgins+, 1993)J/ApJS/91/347 : A 5-GHz VLA Survey of the Galactic Plane (Becker+ 1994)J/A+A/455/971 : Organic molecules in the Gal. center (Requena-Torres+, 2006)J/ApJ/670/1115 : IRS spectra at 38 positions in Gal. center (Simpson+, 2007)J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)J/ApJS/181/227 : Catalog of 24um sources toward Galactic Center (Hinz+, 2009)J/A+A/495/157 : Interstellar extinction in Gal. Center (Schultheis+, 2009)J/ApJ/702/178 : YSOs in the central 400pc of the Galaxy (Yusef-Zadeh+, 2009)J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)J/ApJ/736/133 : Spitzer-IRS study of massive YSOs in gal. center (An+, 2011)J/ApJ/737/73 : Infrared extinction toward the Gal. Centre (Fritz+, 2011)J/AJ/149/64 : MIPSGAL 24{mu}m point source catalog (Gutermuth+, 2015)J/MNRAS/470/1462 : HOPS. III. Dense molecular gas properties (Longmore+, 2017)J/ApJ/857/59 : Spitzer/IRS observations of the Gal. Center (Simpson, 2018)J/A+A/642/A81 : APOGEE cool stars (Schultheis+, 2020)J/A+A/653/A133 : GALACTICNUCLEUS IV. JHKs imaging (Nogueras-Lara+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/930/16https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/930/16http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/930/16https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/930/16https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/930/16http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/930/16GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/930/16/targets (IRTF/SpeX targets (Table 2) and parameter estimates from spectral fitting (Table 3))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/930/16/targets?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/930/16/targets?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/930/16/targets?GETtext/xml+votable180.050000true265.681281-29.8193010.0055555555555555566/28825 28827 28830-28831https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/930/16?format=asciiInfrareddefaultJ/ApJ/930/16/targetsIRTF/SpeX targets (Table 2) and parameter estimates from spectral fitting (Table 3)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSSTGCSSTGC identifiermeta.id;meta.mainchar2MASS2MASS identifier (HHMMSSss+DDMMSSs; J2000)meta.id.crosscharGLONGalactic longitudedegpos.galactic.lonGLAT[-0.23/0.22] Galactic latitudedegpos.galactic.latDateObservation date (UT)time.epochnullableBandsBands ("K" or "K, L")meta.id;instr.filtercharAv[9.5/67.6] Foreground visual extinctionmagphys.absorptionfloate_Av[1.4/42] Av uncertaintymagstat.error;phys.absorptionfloatSpTSpectral typesrc.spTypecharl_tau3.0Limit flag on tau3.0meta.code.error;phys.absorption.opticalDepth;em.IR.3-4umchartau3.0[0.01/4]? Optical depth of the 3um band from solid H_2_O (Section 3.2)phys.absorption.opticalDepth;em.IR.3-4umfloatnullablee_tau3.0[0.01/1]? tau3.0 uncertaintystat.error;phys.absorption.opticalDepth;em.IR.3-4umfloatnullablel_tau3.4Limit flag on tau3.4meta.code.error;phys.absorption.opticalDepth;em.IR.3-4umchartau3.4[0.03/0.4]? Optical depth of the 3.4um hydrocarbon band (Section 3.3)phys.absorption.opticalDepth;em.IR.3-4umfloatnullableSimbadSimbad column added by the CDSmeta.ref.urlchar_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.raindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decindexede_tau3.4[0.01/0.2]? tau3.4 uncertaintystat.error;phys.absorption.opticalDepth;em.IR.3-4umfloatnullablel_tau3.54Limit flag on tau3.54meta.code.error;phys.absorption.opticalDepth;em.IR.3-4umchartau3.54[0.01/0.2]? Optical depth of the 3.54um from the CH_3_OH band (Section 3.4)phys.absorption.opticalDepth;em.opt;em.IR.3-4umfloatnullablee_tau3.54[0.01/0.1]? tau3.54 uncertaintystat.error;phys.absorption.opticalDepth;em.IR.3-4umfloatnullablel_NH2OLimit flag on NH2Ometa.code.error;phys.columnDensitycharNH2O[0.01/6.4]? H_2_O column density1e+18cm**-2phys.columnDensityfloatnullablee_NH2O[0.02/1.6]? NH2O uncertainty1e+18cm**-2stat.error;phys.columnDensityfloatnullablel_NCH3OHLimit flag on NCH3OHmeta.code.error;phys.columnDensitycharNCH3OH[0.02/0.6]? CH_3_OH column density1e+18cm**-2phys.columnDensityfloatnullablee_NCH3OH[0.02/0.2]? NCH3OH uncertainty1e+18cm**-2stat.error;phys.columnDensityfloatnullableCOabsCO absorptionmeta.notecharBrgamBr {gamma} emissionmeta.notechar