Carbon in spiral galaxies from Hubble Space Telescope spectroscopy
Por:
Garnett D.R., Shields G.A., Peimbert M., Torres-Peimbert S., Skillman E.D., Dufour R.J., Terlevich E., Terlevich R.J.
Publicada:
1 ene 1999
Resumen:
We present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M104 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. The most likely hypothesis at present is that stellar winds in massive stars have an important effect on the yields and thus on the evolution of carbon and oxygen abundances. C-to-O and N-to-O abundance ratios in the outer disks of spirals determined to date are very similar to those in dwarf irregular galaxies. This implies that the outer disks of spirals have average stellar-population ages much younger than those of the inner disks.
Filiaciones:
Garnett D.R.:
Department of Astronomy, University of Minnesota, Minneapolis, MN 55455, United States
Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, United States
Shields G.A.:
Department of Astronomy, University of Texas, Austin, TX 78712, United States
Peimbert M.:
Instituto de Astronomía, UNAM, Apdo Postal 70-264, México 04510 D.F., Mexico
Torres-Peimbert S.:
Instituto de Astronomía, UNAM, Apdo Postal 70-264, México 04510 D.F., Mexico
Skillman E.D.:
Department of Astronomy, University of Minnesota, Minneapolis, MN 55455, United States
Dufour R.J.:
Dept. of Space Physics and Astronomy, Rice University, Houston, TX 77251-1892, United States
Terlevich E.:
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, United Kingdom
Terlevich R.J.:
Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, United Kingdom
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