J/ApJS/249/6ivo://CDS.VizieR/J/ApJS/249/6doi:10.26093/cds/vizier.22490006CDSZhang J.S.Liu W.Yan Y.T.Yu H.Z.Liu J.T.Zheng Y.H.Romano D.,Zhang Z.-Y.Wang J.Z.Chen J.L.Wang Y.X.Zhang W.J.Lu H.H.,Chen L.S.Zou Y.P.Yang H.Q.Wen T.Lu F.S.2021-02-19T06:45:00Z2020-11-09T07:53:22ZCDS support team

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

cds-question@unistra.frco-line-emissionmolecular-cloudsmilky-way-galaxyThe interstellar oxygen isotopic ratio of ^18^O/^17^O can reflect the relative amount of the secular enrichment by ejecta from high-mass versus intermediate-mass stars. Previous observations found a Galactic gradient of ^18^O/^17^O, i.e., low ratios in the Galactic center and large values in the Galactic disk, which supports the inside-out formation scenario of our Galaxy. However, there are not many observed objects and, in particular, there are not many at large galactocentric distances. For this reason, we started a systematic study on Galactic interstellar ^18^O/^17^O, through observations of C^18^O and C^17^O multi-transition lines toward a large sample of 286 sources (at least one order of magnitude larger than previous ones), from the Galactic center region to the far outer Galaxy (~22kpc). In this article, we present our observations of J=1-0 lines of C^18^O and C^17^O, with the 12m antenna of the Arizona Radio Observatory (ARO 12m) and the Institut de Radio Astronomie Millimetrique (IRAM) 30m telescopes. Among our IRAM 30m sample of 50 targets, we detected successfully both C^18^O and C^17^O 1-0 lines for 34 sources. Similarly, our sample of 260 targets for ARO 12m observations resulted in the detection of both lines for 166 sources. The C^18^O optical depth effect on our ratio results, evaluated by fitting results of C^17^O spectra with hyperfine components (assuming {tau}_C18O_=4{tau}_C17O_) and our radiative transfer and excitation model nonlocal thermodynamic equilibrium (non-LTE) model calculation for the strongest source, was found to be insignificant. Beam dilution does not seem to be a problem either, which was supported by the fact that there is no systematic variation between the isotopic ratio and the heliocentric distance, and ratios are consistently measured from two telescopes for most of those detected sources. With this study we obtained ^18^O/^17^O isotopic ratios for a large sample of molecular clouds with different galactocentric distances. Our results, though there are still very few detections made for sources in the outer Galaxy, confirm the apparent ^18^O/^17^O gradient of ^18^O/^17^O=(0.10+/-0.03)R_GC_+(2.95+/-0.30), with a Pearson's rank correlation coefficient of R=0.69. This is supported by the newest Galactic chemical evolution model including the impact of massive stellar rotators and novae.2020ApJS..249....6Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/249/6CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+AS/80/149 : IRAS Sources behind the Solar circle (WB89) (Wouterloot+ 1989)J/A+A/430/549 : C^18^O/C^17^O near rho Oph (Wouterloot+, 2005)J/ApJ/724/748 : Galactic anticenter PNe and oxygen abundance (Henry+, 2010)J/MNRAS/403/1413 : Updated stellar yields from AGB models (Karakas, 2010)J/A+A/554/A55 : C^18^O(1-0) and N_2_H^+^(1-0) in L1495/B213 (Hacar+, 2013)J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)J/ApJS/219/28 : C^18^O/C^17^O ratios in the Galactic center (Zhang+, 2015)J/ApJS/237/13 : Yields of 13-120M_{sun}_ massive stars (Limongi+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/249/6https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/249/6http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/249/6https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/249/6https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/249/6http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/249/6GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/249/6/sources (List of sources observed by ARO 12m and IRAM 30m telescopes; table added by CDS)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/249/6/sources?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/249/6/sources?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/249/6/sources?GETtext/xml+votable180.050000true267.0025-27.93559280.005555555555555556Cone search capability for table J/ApJS/249/6/table1 (Isotopic ratios of large molecular clouds)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/249/6/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/249/6/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/249/6/table1?GETtext/xml+votable180.050000true0.178333368.66416670.0055555555555555565/3576 3577 7383 6/1307 1330 1335 1340 1470 1781 1929 1960 1962 2973 3011 3023 3031 3052 3059 3061 3065 3067 3068 3070 3157 3229 3290 3292 3301 3302 3305 3308 3309 3311 3320 3336 3338 3637 3639 3640 3649 3651 3656 3713 3717 3728 3729 3730 3732 3736 3746 3759 3760 14062 14063 14206 14219 14241 14250 14251 14255 14267 14269 14270 14280 14282 14285 14287 14290 14293 14294 14297 14298 14299 14303 14312 14314 14316 14317 14323 14329 14331 14333 14353 14594 14611 14621 14622 14643 14655 14671 14674 14689 14692 14704 14719 15376 15377 15385 15386 15387 15388 15394 15408 15409 15414 15421 15425 15428 15429 15430 15434 15439 15448 15449 15452 15455 15458 15460 15461 15462 15464 15473 15474 15476 15477 15567 15624 15626 15627 15629 15632 15642 15649 15655 15665 15667 15668 15671 15673 15676 15681 15682 15683 15686 15692 15696 15697 15703 15720 15759 15817 21993 22243 22855 23644 23760 23767 23775 23945 23968 23982 24325 24362 24499 28830 28831 28912 29091 29092 29096 29097 29100 29101 29103 29113 29114 29461 30218 30219 30245 30258 30259 30269 30312 30313 30318 30319 30328 30405 30425 30617 30618 30622 30644 30691 30694 30715 39375 42436 42457https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/249/6?format=asciiRadiodefaultJ/ApJS/249/6/sourcesList of sources observed by ARO 12m and IRAM 30m telescopes; table added by CDSSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSource Namemeta.id;meta.maincharprimaryRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainBothDisplay data for sources with both ARO-12m and IRAM-30m detections (link to Table 2)meta.ref.urlintnullableNrNumber of ratio measurements (link to Table 1)meta.ref.urlintnullableJ/ApJS/249/6/table1Isotopic ratios of large molecular cloudsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSource Namemeta.id;meta.maincharm_NameVelocity component of the sourcemeta.code.multipcharFlag[0/1] 1=absorption features close to the emission in the spectrameta.code.errorintf_NameFlags on individual sources (1)meta.codecharRAJ2000? Hour of Right Ascension (J2000) (2)pos.eq.ra;meta.mainnullableDEJ2000? Degree of Declination (J2000) (2)pos.eq.dec;meta.mainnullableRgc[0/22.7]? Galactocentric distancekpcpos.distance;pos.galactocentricfloatnullableDist[0.1/14.2]? Heliocentric distance (2)kpcpos.distancefloatnullableTelTelescope used ("ARO" or "IRAM")instr.setupcharLineMolecular species ("C17O" or "C18O")meta.id;phys.molcharrms[0.006/0.3]? Root-Mean-Square value in TmbKstat.errorfloatnullableI-Tmb[0.06/70.1]? Integrated line intensity of C^18^O and C^17^OK.km/sphot.flux.densityfloatnullablee_I-Tmb[0.01/1.2]? Uncertainty in I-TmbK.km/sstat.errorfloatnullableTpeak[0.03/8.1]? Line peak valuesKphys.temperaturefloatnullableRatio[2.3/7.1]? Frequency-corrected abundance ratiophys.abund;arith.ratiofloatnullablee_Ratio[0.04/2.2]? Uncertainty in Ratiostat.error;arith.ratiofloatnullableJ/ApJS/249/6/table2Comparisons of ARO 12m and IRAM 30m observation results for 7 sources with both C^18^O and C^17^O detectionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSource Namemeta.id;meta.maincharTelTelescope used ("ARO" or "IRAM")instr.setupcharLineMolecular species ("C17O" or "C18O")meta.id;phys.molcharf_LineFlag on Linemeta.codecharrms[0.008/0.2] Root-Mean-Square value in TmbKstat.errorfloatI-Tmb[0.07/48.5] Integrated line intensity of C^18^O and C^17^OK.km/sphot.flux.densityfloate_I-Tmb[0.01/0.3] Uncertainty in I-TmbK.km/sstat.errorfloatTpeak[0.03/7.4] Line peak valuesKphys.temperaturefloatRgc[4.8/13.5]? Galactocentric distancekpcpos.distance;pos.galactocentricfloatnullableDist[1.17/8.2]? Heliocentric distancekpcpos.distancefloatnullableRatio[2.3/5]? frequency-corrected abundance ratiophys.abund;arith.ratiofloatnullablee_Ratio[0.05/0.7]? Uncertainty in Ratiostat.error;arith.ratiofloatnullable