dc.contributor.author | Simon, Joshua D. | |
dc.contributor.author | Kirby, Evan N. | |
dc.contributor.author | Frebel, Anna L. | |
dc.date.accessioned | 2015-02-17T15:59:51Z | |
dc.date.available | 2015-02-17T15:59:51Z | |
dc.date.issued | 2014-04 | |
dc.date.submitted | 2013-12 | |
dc.identifier.issn | 0004-637X | |
dc.identifier.issn | 1538-4357 | |
dc.identifier.uri | http://hdl.handle.net/1721.1/94556 | |
dc.description.abstract | We present Magellan/MIKE and Keck/HIRES high-resolution spectra of six red giant stars in the dwarf galaxy Segue 1. Including one additional Segue 1 star observed by Norris et al., high-resolution spectra have now been obtained for every red giant in Segue 1. Remarkably, three of these seven stars have metallicities below [Fe/H] = –3.5, suggesting that Segue 1 is the least chemically evolved galaxy known. We confirm previous medium-resolution analyses demonstrating that Segue 1 stars span a metallicity range of more than 2 dex, from [Fe/H] = –1.4 to [Fe/H] = –3.8. All of the Segue 1 stars are α-enhanced, with [α/Fe] ~ 0.5. High α-element abundances are typical for metal-poor stars, but in every previously studied galaxy [α/Fe] declines for more metal-rich stars, which is typically interpreted as iron enrichment from supernova Ia. The absence of this signature in Segue 1 indicates that it was enriched exclusively by massive stars. Other light element abundance ratios in Segue 1, including carbon enhancement in the three most metal-poor stars, closely resemble those of metal-poor halo stars. Finally, we classify the most metal-rich star as a CH star given its large overabundances of carbon and s-process elements. The other six stars show remarkably low neutron-capture element abundances of [Sr/H] < –4.9 and [Ba/H] < –4.2, which are comparable to the lowest levels ever detected in halo stars. This suggests minimal neutron-capture enrichment, perhaps limited to a single r-process or weak s-process synthesizing event. Altogether, the chemical abundances of Segue 1 indicate no substantial chemical evolution, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation. | en_US |
dc.description.sponsorship | National Science Foundation (U.S.) (CAREER Grant AST-1255160) | en_US |
dc.language.iso | en_US | |
dc.publisher | IOP Publishing | en_US |
dc.relation.isversionof | http://dx.doi.org/10.1088/0004-637X/786/1/74 | en_US |
dc.rights | Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. | en_US |
dc.source | American Astronomical Society | en_US |
dc.title | SEGUE 1: AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE | en_US |
dc.type | Article | en_US |
dc.identifier.citation | Frebel, Anna, Joshua D. Simon, and Evan N. Kirby. “SEGUE 1: AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE.” The Astrophysical Journal 786, no. 1 (May 1, 2014): 74. © 2014 The American Astronomical Society | en_US |
dc.contributor.department | Massachusetts Institute of Technology. Department of Physics | en_US |
dc.contributor.department | MIT Kavli Institute for Astrophysics and Space Research | en_US |
dc.contributor.mitauthor | Frebel, Anna L. | en_US |
dc.relation.journal | The Astrophysical Journal | en_US |
dc.eprint.version | Final published version | en_US |
dc.type.uri | http://purl.org/eprint/type/JournalArticle | en_US |
eprint.status | http://purl.org/eprint/status/PeerReviewed | en_US |
dspace.orderedauthors | Frebel, Anna; Simon, Joshua D.; Kirby, Evan N. | en_US |
dc.identifier.orcid | https://orcid.org/0000-0002-2139-7145 | |
mit.license | PUBLISHER_POLICY | en_US |
mit.metadata.status | Complete | |