J/AJ/120/1306ivo://CDS.VizieR/J/AJ/120/1306doi:10.26093/cds/vizier.51201306CDSLelievre M.Roy J.R.2023-04-06T16:50:39Z2000-10-23T11:40:32ZCDS support team

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

cds-question@unistra.frgalaxiesphotometryh-ii-regionsvisible-astronomyh-alpha-photometryEmploying deep H{alpha} narrowband imagery, we identified and measured the fluxes of 137 small H II regions in the extreme outer disk (R>=R_25_) of the nearly face-on, Sc I galaxy NGC 628. A majority of these H II regions are located in two faint, outer spiral arms visible in H I maps. The faintest H II regions that could be measured have fluxes of only a few times 10^-16^ergs/cm^2^/s, which correspond to luminosities of 10^36^ergs/s, or a fraction of the Orion Nebula luminosity. The most distant object detected is at R~27kpc from the galaxy center. The massive star formation rate, as measured from the azimuthally averaged H{alpha} flux, is consistent with a monotonic decrease as far as R~1.3R_25_ (20kpc), where there is a sharp drop. The Schmidt law for the whole disk of NGC 628 corresponds to a relatively steep power law with n=2.9+/-0.2, but it "fails" below {Sigma}gas<=4M_{sun}_/pc^2^; the index depends strongly on the CO data used. We derived the luminosity function (LF) of 598 H II regions over the whole disk, and we compared the shapes of the cumulative LFs between R>=R_25_ and R<R_25_; the LF of the outer regions is significantly steeper than that of the inner regions.2000AJ....120.1306Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/120/1306CatalogResearchIsServedByTAP VizieR generic servicerelated-toVII/20 : Catalogue of HII Regions (Sharpless 1959)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/120/1306https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/120/1306http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/120/1306https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/120/1306https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/120/1306http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/120/1306GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/120/1306/table2Positions, galactocentric radii, fluxes, luminosities, and star formation rates of the H II regions at R>=R_25_recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintEWPosH II region position (1)arcsecpos.projintNSPosH II region position (1)arcsecpos.projintGalRadH II galactocentric radiusarcsecpos.projintFluxH II region flux (10^-16^ergs/cm^2^/s)1e-16mW.m**-2phot.flux;em.line.Halphafloate_FluxUncertainty in Flux1e-16mW.m**-2stat.errorfloatLumH II region luminosity (10^36^ergs/s)1e+29Wphys.luminosityfloate_LumUncertainty in Lum1e+29Wstat.errorfloatSFRH II region star formation rate1e-05solMass.yr**-1phys.SFRfloate_SFRUncertainty in SFR1e-05solMass.yr**-1stat.errorfloat