J/ApJ/513/168ivo://CDS.VizieR/J/ApJ/513/168doi:10.26093/cds/vizier.15130168CDSGarnett D.R.Shields G.A.Peimbert M.Torres-Peimbert S.SkillmanE.D.Dufour R.J.Terlevich E.Terlevich R.J.2000-03-16T07:55:52Z2000-03-16T08:55:40ZCDS support team

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

cds-question@unistra.frchemical-abundancesgalaxiesspectroscopyultraviolet-astronomyWe present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the Hubble Space Telescope. The ratios of C to O increase systematically with O/H in both galaxies, from log(C/O){~=}-0.8 at log(O/H){~=}-4.0 to log(C/O){~=}-0.1 at log(O/H){~=}-3.4. C/N shows no correlation with O/H. The rate of increase of C/O is somewhat uncertain because of uncertainty as to the appropriate UV reddening law and uncertainty in the metallicity dependence on grain depletions. However, the trend of increasing C/O with O/H is clear, confirming and extending the trend in C/O indicated previously from observations of irregular galaxies. Our data indicate that the radial gradients in C/H across spiral galaxies are steeper than the gradients in O/H. Comparing the data to chemical-evolution models for spiral galaxies shows that models in which the massive star yields do not vary with metallicity predict radial C/O gradients that are much flatter than the observed gradients.1999ApJ...513..168Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/513/168CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/104/92 : HII Regions Properties in M101 (Scowen+ 1992)J/A+AS/91/285 : HII galaxies spectrophotometric catalogue (Terlevich+, 1991)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/513/168https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/513/168http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/513/168https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/513/168https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/513/168http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/513/168GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapHSTUVdefaultJ/ApJ/513/168/table2Spectra for M101 and NGC 2403 HII regionsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.intNameH II region namecharIonIoncharWaveWavelength of Ionnmfloatl_FluxIndicates a lower limit in FluxcharFluxObserved flux relative to H{beta}floate_Flux? Uncertainty (1{sigma}) in Fluxfloatnullablel_F3.1Indicates a lower limit in F3.1charF3.1Extinction Corrected flux (R=3.1) relative to H{beta}floate_F3.1? Uncertainty (1{sigma}) in F3.1floatnullablel_F5Indicates a lower limit in F5charF5Extinction Corrected flux (R=5) relative to H{beta}floate_F5? Uncertainty (1{sigma}) in F5floatnullableA3.1Extinction (R=3.1) at H{beta}magfloate_A3.1Uncertainty in A3.1magfloatA5Extinction (R=5) at H{beta}magfloate_A5Uncertainty in A5magfloat