R. Michael Rich, Livia Origlia, Elena Valenti
We report abundance analysis for 30 M giant stars in two inner Galactic bulge
fields at (l,b)=(0,-1.75) deg and at (l,b)=(1,-2.65) deg, based on R=25,000
infrared spectroscopy from 1.5-1.8um using NIRSPEC at the Keck II telescope. We
find iron abundances of <[Fe/H]>=-0.16 +/- 0.03 dex with a 1-sigma dispersion
of 0.12 +/- 0.02 and <[Fe/H]>=-0.21 +/- 0.02 dex, with a 1-sigma dispersion of
0.09+/- 0.016 for the (l,b)=(0,-1.75) and (l,b)=(1,-2.65) deg fields,
respectively. In agreement with all prior studies, we find enhanced [alpha/Fe]
of +0.3 dex. We confirm the lack of any major vertical abundance or composition
gradient in the innermost ~600 pc between Baade's window and 150 pc from the
Galactic plane. We also confirm that the known enhancement of alpha elements
observed between 500 and 1000 pc from the nucleus is also present over the
volume of the inner bulge and may therefore be presumed to be a general
characteristic of bulge/bar stars within 1 kpc of the Galactic Center.
View original:
http://arxiv.org/abs/1112.0306
No comments:
Post a Comment