MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. IV. ALPHA ELEMENT DISTRIBUTIONS IN MILKY WAY SATELLITE GALAXIES
- California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
- University of California Observatories/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
- Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
We derive the star formation histories of eight dwarf spheroidal (dSph) Milky Way satellite galaxies from their alpha element abundance patterns. Nearly 3000 stars from our previously published catalog comprise our data set. The average [{alpha}/Fe] ratios for all dSphs follow roughly the same path with increasing [Fe/H]. We do not observe the predicted knees in the [{alpha}/Fe] versus [Fe/H] diagram, corresponding to the metallicity at which Type Ia supernovae begin to explode. Instead, we find that Type Ia supernova ejecta contribute to the abundances of all but the most metal-poor ([Fe/H] < -2.5) stars. We have also developed a chemical evolution model that tracks the star formation rate, Types II and Ia supernova explosions, and supernova feedback. Without metal enhancement in the supernova blowout, massive amounts of gas loss define the history of all dSphs except Fornax, the most luminous in our sample. All six of the best-fit model parameters correlate with dSph luminosity but not with velocity dispersion, half-light radius, or Galactocentric distance.
- OSTI ID:
- 21567569
- Journal Information:
- Astrophysical Journal, Vol. 727, Issue 2; Other Information: DOI: 10.1088/0004-637X/727/2/79; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
The Populations of Carina. II. Chemical Enrichment
INSIGHT INTO THE FORMATION OF THE MILKY WAY THROUGH COLD HALO SUBSTRUCTURE. II. THE ELEMENTAL ABUNDANCES OF ECHOS