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BOO-1137—AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOÖTES I
- Source :
- The Astrophysical Journal. 711:350-360
- Publication Year :
- 2010
- Publisher :
- American Astronomical Society, 2010.
-
Abstract
- We present high-resolution, high-S/N spectra of an extremely metal- poor giant star Boo-1137 in the "ultra-faint" dwarf spheroidal galaxy (dSph) Bootes I (absolute magnitude Mv ~ -6.3). With [Fe/H] = -3.7, this the most metal-poor star yet identified in an ultra-faint dSph. Comparison of relative abundances, [X/Fe], for some 15 elements with those of the extremely metal-poor giants of the Galactic halo shows Boo-1137 is "normal" with respect to C and N, the odd-Z elements Na and Al, the Fe-peak elements, and the n-capture elements Sr and Ba, in comparison with the bulk of the halo with [Fe/H] < -3.0. The alpha- elements Mg, Si, Ca, and Ti are all higher by Delta[X/Fe] ~ 0.2 than average halo values. Monte-Carlo analysis indicates Delta[alpha/Fe] values this large are expected with probability ~ 0.02. The abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in Fe abundances we reported earlier. The similarity of most of the Boo-1137 relative abundances with respect to halo values, and the fact that the alpha-elements are all offset by a similar small amount from the halo averages, points to the same underlying galaxy-scale stellar initial mass function, but that Boo-1137 likely originated in a star-forming region where the abundances reflect either poor mixing of supernova (SN) ejecta, or poor sampling of the SN progenitor mass range, or both.<br />Comment: 33 pages, 6 figures, submitted to Astrophysical Journal
- Subjects :
- Physics
Absolute magnitude
Initial mass function
Astronomy and Astrophysics
BOOTES
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics
Giant star
Astrophysics - Astrophysics of Galaxies
Dwarf spheroidal galaxy
Galactic halo
Supernova
Space and Planetary Science
Astrophysics::Solar and Stellar Astrophysics
Halo
Astrophysics::Galaxy Astrophysics
Subjects
Details
- ISSN :
- 15384357 and 0004637X
- Volume :
- 711
- Database :
- OpenAIRE
- Journal :
- The Astrophysical Journal
- Accession number :
- edsair.doi.dedup.....c5c7ce75186913260270d880e65334bc