A Spectroscopic Study of OB Stars Located in the Outer Galactic Disk

Poster to be presented on IAU Symposium "New WIndows on Massive Stars".

 

Abstract

Abundance gradients are generally observed in all galaxies, with their metallicities decreasing outwards from the galactic centers. The abundance slopes for different elements may vary depending on the galactic morphology. In our Galaxy, the radial abundance gradients remain somewhat uncertain on the outer parts of the Galactic disk, due to the small number of studied stars located beyond the Perseus Arm. The aim of this study is to provide a large abundance database of distant stars in order to better constrain the Galactic gradient in the Outer Disk. We have obtained high-resolution, echelle spectra for a sample of 137 OB stars located towards the Galactic anticenter using the 6.5m Magellan Clay telescope + MIKE spectrograph. A subsample of 50 single stars presenting sharp absorption lines has been selected to carry out the abundance analysis. Stellar parameters and silicon abundances are derived consistently based on non-LTE synthesis of hydrogen, helium, and silicon lines, requiring ionization balance of SiII/III/IV and O I/II/III. In this work, we present preliminary abundance results of our analysis.

 

Acknowledgements

We acknowledge financial support of National Science Foundation, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

 and the International Astronomomic Union. This research has made use of the SIMBAD database,
operated at CDS, Strasbourg, France, and of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration, 2013).