Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-10-03
Astronomy and Astrophysics
Astrophysics
5 pages, 3 figures, accepted by Astrophysical Journal Letters
Scientific paper
10.1086/595001
We report on the abundance analysis of two red giants in the faint Hercules dwarf spheroidal (dSph) galaxy. These stars show a remarkable deficiency in the neutron-capture elements, while the hydrostatic alpha-elements (O, Mg) are strongly enhanced. Our data indicate [Ba/Fe] and [Mg/Fe] abundance ratios of <-2 dex and ~+0.8 dex, respectively, with essentially no detection of other n-capture elements. In contrast to the only other dSph star with similar abundance patterns, Dra 119, which has a very low metallicity at [Fe/H]=-2.95 dex, our objects, at [Fe/H]~-2.0 dex, are only moderately metal poor. The measured ratio of hydrostatic/explosive alpha-elements indicates that high-mass (~35 M_sun) Type II supernovae progenitors are the main, if not only, contributors to the enrichment of this galaxy. This suggests that star formation and chemical enrichment in the ultrafaint dSphs proceeds stochastically and inhomogeneously on small scales, or that the IMF was strongly skewed to high mass stars. The neutron capture deficiencies and the [Co/Fe] and [Cr/Fe] abundance ratios in our stars are similar to those in the extremely low metallicity Galactic halo. This suggests that either our stars are composed mainly of the ejecta from the first, massive, population III stars (but at moderately high [Fe/H]), or that SN ejecta in the Hercules galaxy were diluted with ~30 times less hydrogen than typical for extreme metal-poor stars.
Belokurov Vasily
Grebel Eva Katharina
Koch Alan
McWilliam Andrew
Zucker Daniel B.
No associations
LandOfFree
The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Highly Unusual Chemical Composition of the Hercules Dwarf Spheroidal Galaxy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-541398