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The Chemical Enrichment of the Diffuse Gas in the Outer Galaxy and the Abundance Gradient of the Milky Way

Published online by Cambridge University Press:  01 June 2007

Limin Song ,
Todd M. Tripp ,
David V. Bowen  and
Kenneth R. Sembach
Limin Song
Affiliation:
Astronomy Department, University of Massachusetts, Amherst, MA 01002, USA email: [email protected], [email protected]
Todd M. Tripp
Affiliation:
Astronomy Department, University of Massachusetts, Amherst, MA 01002, USA email: [email protected], [email protected]
David V. Bowen
Affiliation:
Princeton University Observatory, Princeton, NJ 08544, USA email: [email protected]
Kenneth R. Sembach
Affiliation:
Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA email: [email protected]
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Abstract

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Using data from HST/STIS (Hubble Space Telescope / Space Telescope Imaging Spectrograph) and FUSE (Far Ultraviolet Spectroscopic Explorer) toward two QSOs, H1821+643 and HS0624+6907, we find that the overall metallicity of the Galactic “Outer Arm” is Z=0.3−0.5 Z⊙ with underabundant nitrogen and little depletion by dust. The results are consistent with those based on H II region measurements in the outer galaxy and provide additional constrains on models of the Galactic abundance gradient and Milky Way (MW) chemical evolution. The lower metallicity observed in the outer galaxy is consistent with abundance patterns observed in higher redshift damped Lyα absorbers (DLAs) extrapolated to z=0. The slow metallicity evolution of DLAs could be due to the larger cross sections of the outer regions of galaxies combined with the observed metallicity gradients.

Keywords

abundance gradientmetallicity
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S244: Dark Galaxies and Lost Baryons , June 2007 , pp. 381 - 382
Copyright
Copyright © International Astronomical Union 2008

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