J/MNRAS/536/3803ivo://CDS.VizieR/J/MNRAS/536/3803CDSBosomworth C.Forbrich J.Lada C.J.Caldwell N.Kobayashi C.,Viaene S.2026-01-09T12:22:09Z2026-01-09T10:14:34ZCDS support team

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

cds-question@unistra.frh-i-line-emissionh-ii-regionschemical-abundancesextinctiongalaxiesmolecular-cloudsspectroscopyvisible-astronomyinfrared-astronomyinterstellar-mediumFrom a spectroscopic survey of candidate H ii regions in the Andromeda Galaxy (M31) with MMT/Hectospec, we have identified 294 H ii regions using emission line ratios and calculated elemental abundances from strong-line diagnostics (values ranging from subsolar to supersolar) producing both oxygen and nitrogen radial abundance gradients. The oxygen gradient is relatively flat, while the nitrogen gradient is significantly steeper, indicating a higher N/O ratio in M31's inner regions, consistent with recent simulations of galaxy chemical evolution. No strong evidence was found of systematic galaxy-scale trends beyond the radial gradient. After subtracting the radial gradient from abundance values, we find an apparently stochastic and statistically significant scatter of standard deviation 0.06dex, which exceeds measurement uncertainties. One explanation includes a possible collision with M32 200-800Myr ago. Using the two-point correlation function of the oxygen abundance, we find that, similar to other spiral galaxies, M31 is well-mixed on sub-kpc scales but less so on larger (kpc) scales, which could be a result of an exponential decrease in mixing speed with spatial scale, and the aforementioned recent merger. Finally, the MMT spectroscopy is complemented by a dust continuum and CO survey of individual giant molecular clouds, conducted with the Submillimeter Array (SMA). By combining the MMT and SMA observations, we obtain a unique direct test of the oxygen abundance dependence of the {alpha}'(^12^CO) factor which is crucial to convert CO emission to dust mass. Our results suggest that within our sample there is no trend of the {alpha}'(^12^CO) with oxygen abundance.2025MNRAS.536.3803Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/536/3803CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/143 : Revised Bologna Catalog of M31 clusters, V.5 (Galleti+ 2012)V/156 : LAMOST DR7 catalogs (Luo+, 2019)J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006)J/AJ/142/139 : A new catalog of HII regions in M31 (Azimlu+, 2011)J/ApJ/758/133 : Metallicity profile of M31 HII regions and PNe (Sanders+, 2012)J/ApJ/798/58 : HELGA VI. Giant mol. cloud associations in M31 (Kirk+, 2015)J/AJ/152/62 : Revised LGGS UBVRI phot. of M31 and M33 stars (Massey+, 2016)J/MNRAS/455/2627 : Oxygen abundance gradient in M81 (Arellano-Cordova+, 2016)J/MNRAS/465/4180 : H{alpha} stars in M31 HST photometry (Prichard+, 2017)J/ApJ/868/55 : Large-scale struct. of M31 halo. II. PAndAS (McConnachie+, 2018)J/ApJ/852/2 : CO emission from 78 WISE HII region in the OSC (Wenger+, 2018)J/ApJ/887/114 : VLA ~8-10GHz obs. of WISE Galactic HII regions (Wenger+, 2019)J/ApJ/887/80 : Gas phase oxygen abundances for HII regions (Kreckel+, 2019)J/ApJS/254/36 : Southern HII Region Discov. Surv. II. Full cat (Wenger+, 2021)J/ApJ/925/76 : M33 with LAMOST surv. sp. I. PNe & HII regions (Alexeeva+, 2022)J/A+A/658/A51 : New M31 star cluster candidates (Wang+, 2022)J/ApJ/954/206 : A GCs search in M31 with Gaia, PS1, LAMOST,PAndAS (Wang+, 2023)J/ApJ/943/137 : Deep NIR Subaru phot. in Sh 2-209 HII region (Yasui+, 2023)J/A+A/691/A173 : HII in galaxies abundances (Brazzini+, 2024)J/A+A/694/A61 : Sulphur abundance distribution of HII galaxies (Gavilan+, 2025)J/AJ/169/174 : M31 nebulae, clusters, & supergiants with LAMOST (Chen+, 2025)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/536/3803https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/536/3803http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/536/3803https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/536/3803https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/536/3803http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/536/3803GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/536/3803/table1 (Emission line flux ratios (relative to H{beta}=100) for M31 H_II_ regions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/536/3803/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/536/3803/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/536/3803/table1?GETtext/xml+votable180.050000true9.804208340.69580.005555555555555556Cone search capability for table J/MNRAS/536/3803/table2 (Chemical abundances for M31 H_II_ regions)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/536/3803/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/536/3803/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/536/3803/table2?GETtext/xml+votable180.050000true9.804208340.69580.0055555555555555566/2622-2623 2666-2667 2708-2709 2752https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/536/3803?format=asciiOpticalInfraredRadiodefaultJ/MNRAS/536/3803/table1Emission line flux ratios (relative to H{beta}=100) for M31 H_II_ regionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDt1Sequence number identifier from Table 1 (1)meta.id;meta.mainintprimaryRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainOII-3727[84.5/2123.3] The [O II] 3727A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_OII-3727[0.3/216.2] Uncertainty in [O II] 3727A (3)stat.error;phot.flux;spect.linefloatOIII-4959[3.3/148.9] The [O III] 4959A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_OIII-4959[0.1/18.3] Uncertainty in [O III] 4959A (3)stat.error;phot.flux;spect.linefloatOIII-5007[9.4/452.1] The [O III] 5007A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_OIII-5007[0.1/34.9] Uncertainty in [O III] 5007A (3)stat.error;phot.flux;spect.linefloatNII-6548[5.9/85.3] The [N II] 6548A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_NII-6548[0.1/8.1] Uncertainty in [N II] 6548A (3)stat.error;phot.flux;spect.linefloatHa[264.7/301.2] The H{alpha} line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_Ha[0.1/15.2] Uncertainty in H{alpha} (3)stat.error;phot.flux;spect.linefloatNII-6584[18.1/255.6] The [N II] 6584A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_NII-6584[0.1/9.9] Uncertainty in [N II] 6584A (3)stat.error;phot.flux;spect.linefloatSII-6717[2.4/67.4] The [S II] 6717A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_SII-6717[0.1/6.2] Uncertainty in [S II] 6717A (3)stat.error;phot.flux;spect.linefloatSII-6731[4.2/52.1] The [S II] 6731A line flux ratio (2)phot.flux;arith.ratio;spect.linefloate_SII-6731[0/4.8] Uncertainty in [S II] 6731A (3)stat.error;phot.flux;spect.linefloatJ/MNRAS/536/3803/table2Chemical abundances for M31 H_II_ regionsIDt1Sequence number identifier from Table 1 (column added by CDS) (1)meta.id;meta.numberintprimaryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDt2Sequence number identifier from Table 2meta.id;meta.mainintRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.mainRad[4.07/20.71] Galactocentric Radius (2)kpcphys.size.radius;pos.galactocentricfloatAv[0.01/4.7] The V band extinction (3)magphys.absorptionfloate_Av[0.01/0.89] Uncertainty in Av (4)magstat.error;phys.absorptionfloat(O/H)Rcal[8.21/8.84] Pilyugin+2016 R-calibration calculation of log(O/H)+12 (5)phys.abundfloate_(O/H)Rcal[0.01/0.07] Uncertainty in (O/H)Rcal (4)stat.error;phys.abundfloat(O/H)Scal[8.37/8.83] Pilyugin+2016 S-calibration calculation of log(O/H)+12 (5)phys.abundfloate_(O/H)Scal[0.01/0.04] Uncertainty in (O/H)Scal (4)stat.error;phys.abundfloat(O/H)Z94[6.79/9.18] Zaritsky+1994 calculation of log(O/H)+12 (5)phys.abundfloate_(O/H)Z94[0.01/0.29] Uncertainty in (O/H)Z94 (4)stat.error;phys.abundfloat(N/H)Rcal[6.64/8.61] Pilyugin+2016 R-calibration calculation of log(N/H)+12 (5)phys.abundfloate_(N/H)Rcal[0.01/0.21] Uncertainty in (N/H)Rcal (4)stat.error;phys.abundfloat