Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2009-02-15
Astrophys.J.708:560-583,2010
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
Accepted for publication in ApJ, emulateapj-style, 29 pages incl. figures and tables
Scientific paper
10.1088/0004-637X/708/1/560
We present Keck/HIRES observations of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices. These observations include the first high-resolution spectroscopic observations of extremely metal-poor stars ([Fe/H]<-3.0) stars not belonging to the Milky Way (MW) halo field star population. We obtain abundance measurements and upper limits for 26 elements between carbon and europium. The entire sample of stars spans a range of -3.2<[Fe/H]<-2.3, and we confirm that each galaxy contains a large intrinsic spread of Fe abundances. A comparison with MW halo stars of similar metallicities reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and the MW halo for the light, alpha and iron-peak elements (C to Zn). This agreement contrasts with the results of earlier studies of more metal-rich stars (-2.5<[Fe/H]<-1.0) in more luminous dwarf spheroidal galaxies (dSphs), which found significant abundance discrepancies with respect to the MW halo data. The abundances of neutron-capture elements (Sr to Eu) in the ultra-faint dwarf galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]>-3.0. Our results are broadly consistent with a galaxy formation model that predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]>-2.5) of the MW halo, but we also suggest that the faintest known dwarfs may be the primary contributors to the metal-poor end of the MW halo metallicity distribution.
Frebel Anna
Geha Marla
Simon Joshua D.
Willman Beth
No associations
LandOfFree
High-Resolution Spectroscopy of Extremely Metal-Poor Stars in the Least Evolved Galaxies: Ursa Major II and Coma Berenices 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 High-Resolution Spectroscopy of Extremely Metal-Poor Stars in the Least Evolved Galaxies: Ursa Major II and Coma Berenices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-Resolution Spectroscopy of Extremely Metal-Poor Stars in the Least Evolved Galaxies: Ursa Major II and Coma Berenices will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-718075