J/MNRAS/507/5106ivo://CDS.VizieR/J/MNRAS/507/5106doi:10.26093/cds/vizier.75075106CDSKinson D.A.Oliveira J.M.Van Loon J.T.2024-08-21T20:18:37Z2022-11-13T17:04:57ZCDS support team

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

cds-question@unistra.frgalaxiesyoung-stellar-objectsmillimeter-astronomyphotometrysubmillimeter-astronomyinfrared-photometryWe present a supervised machine learning methodology to classify stellar populations in the Local Group dwarf-irregular galaxy NGC 6822. Near-IR colours (J-H, H-K, and J-K), K-band magnitudes and far-IR surface brightness (at 70 and 160um) measured from Spitzer and Herschel images are the features used to train a Probabilistic Random Forest (PRF) classifier. Point-sources are classified into eight target classes: young stellar objects (YSOs), oxygen- and carbon-rich asymptotic giant branch stars, red giant branch and red supergiant stars, active galactic nuclei, massive main-sequence stars, and Galactic foreground stars. The PRF identifies sources with an accuracy of ~90 per cent across all target classes rising to ~96 per cent for YSOs. We confirm the nature of 125 out of 277 literature YSO candidates with sufficient feature information, and identify 199 new YSOs and candidates. Whilst these are mostly located in known star-forming regions, we have also identified new star formation sites. These YSOs have mass estimates between ~15 and 50M_{sun}_, representing the most massive YSO population in NGC 6822. Another 82 out of 277 literature candidates are definitively classified as non-YSOs by the PRF analysis. We characterize the star formation environment by comparing the spatial distribution of YSOs to those of gas and dust using archival images. We also explore the potential of using (unsupervised) t-distributed stochastic neighbour embedding maps for the identification of the same stellar population classified by the PRF.2021MNRAS.507.5106Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/507/5106CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/892/91 : UKIRT NIR and Spitzer MIR phot. in NGC 6822 (Hirschauer+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/507/5106https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/507/5106http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/507/5106https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/507/5106https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/507/5106http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/507/5106GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/507/5106/table1 (Positions, measurements, and their uncertainties (where available) as well as source classification from the training set)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/507/5106/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/507/5106/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/507/5106/table1?GETtext/xml+votable180.050000true296.22588-14.7217190.005555555555555556Cone search capability for table J/MNRAS/507/5106/table3 (Catalogue of YSOs and YSO candidates in NGC 6822 classified using the PRF analysis)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/507/5106/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/507/5106/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/507/5106/table3?GETtext/xml+votable180.050000true296.26883-14.723438890.0055555555555555565/8263 8269 8274-8275 8278 8280-8281 8324 8326 6/29716 29718 33073 33091 33094-33095 33106 33110 33293-33295 33316-33317 33319 33328-33329 375447.952274030004205e-20 1.7798557115773645e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/507/5106?format=asciiInfraredMillimeterdefaultJ/MNRAS/507/5106/table1Positions, measurements, and their uncertainties (where available) as well as source classification from the training setrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLARIDIdentification numbermeta.id;meta.mainintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainKmag? K magnitudemagphot.mag;em.IR.Kdoublenullablee_Kmag? rms uncertainty on Kmagmagstat.error;phot.magdoublenullablemu70um? Surface brightness at 70umMJy/srphot.flux.density.sb;em.IR.60-100umdoublenullablemu160um? Surface brightness at 160umMJy/srphot.flux.density.sb;em.mm.1500-3000GHzdoublenullableJ-H? J-H colour indexmagphot.color;em.IR.J;em.IR.Hdoublenullablee_J-H? rms uncertainty on J-Hmagstat.error;phot.color;em.IR.JdoublenullableH-K? H-K colour indexmagphot.color;em.IR.H;em.IR.Kdoublenullablee_H-K? rms uncertainty on H-Kmagstat.error;phot.color;em.IR.HdoublenullableJ-K? J-K colour indexmagphot.color;em.IR.J;em.IR.Kdoublenullablee_J-K? rms uncertainty on J-Kmagstat.error;phot.color;em.IR.JdoublenullableType[0/8] Type (1)meta.codeintTSExt[*] * for TS Extentionmeta.codecharJ/MNRAS/507/5106/table3Catalogue of YSOs and YSO candidates in NGC 6822 classified using the PRF analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainJmag? J magnitudemagphot.mag;em.IR.Jdoublenullablee_Jmag? J magnitude errormagstat.error;phot.magdoublenullableHmag? H magnitudemagphot.mag;em.IR.Hdoublenullablee_Hmag? H magnitude errormagstat.error;phot.magdoublenullableKmag? K magnitudemagphot.mag;em.IR.Kdoublenullablee_Kmag? K magnitude errormagstat.error;phot.magdoublenullableYSO?YSO, YSO Candidate or TS Extentionmeta.notecharPrevID[J19/H20 ] Previous name J19/H20 (1)meta.codechar