J/A+A/572/A26ivo://CDS.VizieR/J/A+A/572/A26doi:10.26093/cds/vizier.35720026CDSFusco F.Buonanno R.Hidalgo S.L.Aparicio A.Pietrinferni A.Bono G.,Monelli M.Cassisi S.2017-07-04T07:08:16Z2014-11-24T07:54:58ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryhst-photometrystellar-distanceWe present a detailed photometric study of the dwarf irregular galaxy NGC 6822 aimed at investigating the properties of its stellar populations, and in particular, the presence of stellar radial gradients. Our goal is to analyze the stellar populations in six fields, which cover the whole bar of this dwarf galaxy. We derived the quantitative star formation history (SFH) of the six fields using the IAC method, involving IAC-pop/MinnIAC codes. The solutions we derived show an enhanced star formation rate (SFR) in fields 1 and 3 during the last 500Myr. The SFRs of the other fields almost extinguish at very recent epochs. We study the radial gradients of the SFR. We consider the total mass converted into stars in two time intervals (between 0 and 0.5Gyr ago and between 0.5 and 13.5Gyr ago). We find that the scale lengths of the young and intermediate-old populations are perfectly compatible, with the exception of the young populations in fields 1 and 3. The recent SF in these two fields is larger than in the other ones. This might be an indication that in these two fields we are sampling incipient spiral arms. Further evidence and new observations are required to prove this hypothesis. In addition, we derived the age-metallicity relations. As expected, for all of the fields the metallicity increases with time. We do not observe any radial gradient in the metallicity.2014A&A...572A..26Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/572/A26CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/121/2020 : CTIO and WFPC2 photometry in NGC 6822 (Bianchi+, 2001)J/A+A/429/837 : NGC 6822 late-type stars IJKs photometry (Cioni+, 2005)J/A+A/454/717 : NGC 6822 C and AGB stars near-IR photometry (Kang+, 2006)J/A+A/456/905 : NGC 6822 C stars JKs, i'g'r' photometry (Demers+, 2006)J/AJ/132/378 : HST and UV photometry of NGC 6822 (Bianchi+, 2006)J/AJ/132/1372 : Chandra observation of NGC 6822 (Tennant+, 2006)J/A+A/537/A108 : NGC 6822 AGB spectroscopic catalogue (Kacharov+, 2012)J/ApJ/730/88 : NGC 6822 star-forming regions from UV data (Efremova+, 2011)J/A+A/540/A135 : AGB population of NGC 6822 (Sibbons+, 2012)J/A+A/548/A129 : HST photometry in NGC 6822 (Fusco+, 2012)J/MNRAS/428/2216 : JHKs photometry of AGB stars in NGC 6822 (Whitelock+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/572/A26https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/572/A26http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/572/A26https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/572/A26https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/572/A26http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/572/A26GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/572/A26/ngc6822 (HST/ACS photometry in the irregular galaxy)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/572/A26/ngc6822?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/572/A26/ngc6822?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/572/A26/ngc6822?GETtext/xml+votable180.050000true295.860114167-14.53931750.0055555555555555566/297182.3657755224268815e-19 4.369938604086476e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/572/A26?format=asciiOpticaldefaultJ/A+A/572/A26/ngc6822HST/ACS photometry in the irregular galaxyrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFSimbad column added by the CDSobs.fieldcharID[1/13423] Star identification numbermeta.id;meta.mainintXpos[0/4096] X coordinate in pixelspixpos.cartesian.xdoubleYpos[0/4096] Y coordinate in pixelspixpos.cartesian.ydoubleF475W[18.3/30.5] HST/ACS F475W Vega magnitudemagphot.mag;em.opt.Bfloate_F475WError associated to F475W magnitudemagstat.errorfloatF814W[16.7/58.9] HST/ACS F814W Vega magnitudemagphot.mag;em.opt.Ifloate_F814WError associated to F814W magnitudemagstat.errorfloatchi[1/50] Mean value of the {chi} image-quality DAOPHOT index (close to 1 is good)stat.fit.paramfloatSharp[-5/15] Mean value of the sharp image-quality index (stars with |Sharp|<=0.5 were considered)stat.fit.paramfloatRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainChip[1/2] Chip number of the camera (1=WFC1, 2=WFC2)meta.id;instrint