THE CHEMICAL EVOLUTION OF THE DRACO DWARF SPHEROIDAL GALAXY

By J. Cohen, Wenjin Huang. 2009

143 citations recorded by the source corpus.

We present an abundance analysis based on high-resolution spectra of eight stars selected to span the full range in metallicity in the Draco dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from −1.5 to −3.0 dex. Combining our sample with previously published work for a total of 14 luminous Draco giants, we show that the abundance ratios [Na/Fe], [Mg/Fe], and [Si/Fe] for the Draco giants overlap those of Galactic halo giants at the lowest [Fe/H] probed, but are significantly lower for the higher Fe-metallicity Draco stars. For the explosive α-elements Ca and Ti, the abundance ratios for Draco giants with [Fe/H] > − 2.4 dex are approximately constant and slightly subsolar, well below values characteristic of Galactic halo stars. The s-process contribution to the production of heavy elements begins at significantly lower Fe metallicity than in the Galactic halo. Using a toy model we compare the behavior of the abundance ratios within the sample of Draco giants with those from the literature of Galactic globular clusters, and the Carina and Sgr dSph galaxies. The differences appear to be related to the timescale for buildup of the heavy elements, with Draco having the slowest rate. We note the presence of a Draco giant with [Fe/H] <−3.0 dex in our sample, and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies accreted later.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/d792c512dd8a1164354442f776ae00f88d4aaaa2

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. J. Simon
2. E. Kirby
3. M. Geha
4. P. Guhathakurta
5. J. Cohen
6. A. Frebel
7. James S. Bullock
8. B. Willman

In Instrumentation

1. J. Simon
2. M. Geha
3. E. Kirby
4. P. Guhathakurta
5. J. Cohen
6. A. Frebel
7. S. Majewski
8. B. Willman

Citations in the corpus

• MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. III. METALLICITY DISTRIBUTIONS OF MILKY WAY DWARF SATELLITE GALAXIES (2010, background): “Since then, extremely metal-poor stars have been discovered in dSphs (Kirby et al. 2008b, 2009; Geha et al. 2009; Cohen & Huang 2009, 2010; Frebel et al. 2010a,b; Simon et al. 2010a,b; Norris et al. 2010a,b; Starkenburg et al. 2010; Tafelmeyer et al. 2010).”
• MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. II. CATALOG OF STARS IN MILKY WAY DWARF SATELLITE GALAXIES (2010, methodology): “The discussion of the Sextans CMD similarly applies to the Draco CMD. Fourteen stars in Draco have been observed with high-resolution spectroscopy (Shetrone et al. 1998, 2001; Fulbright et al. 2004; Cohen & Huang 2009).”
• HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: URSA MAJOR II and COMA BERENICES (2009, background): “Con- 13 During the completion of this paper, Cohen & Huang (2009) also obtained Sr abundances for their sample of Draco stars. servatively, one could regard this measurement as an upper limit, which would suggest an even more extreme underabundance of Ba.”