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Title: Mining the Sloan digital sky survey in search of extremely α-poor stars in the galaxy

Abstract

As we know, the majority of metal-poor Galactic halo stars appear to have chemical abundances that were enhanced by α-elements (e.g., O, Mg, Si, Ca, and Ti) during the early stage of the Galaxy. Observed metal-poor halo stars preserved this pattern by exhibiting abundance ratios [α/Fe] ∼+0.4. A few striking exceptions that show severe departures from the general enhanced α-element chemical abundance trends of the halo have been discovered in recent years. They possess relatively low [α/Fe] compared to other comparable-metallicity stars, with abundance ratios over 0.5 dex lower. These stars may have a different chemical enrichment history from the majority of the halo. Similarly, low-α abundances are also displayed by satellite dwarf spheroidal (dSph) galaxies. We present a method to select extremely α-poor (EAP) stars from the SDSS/SEGUE survey. The method consists of a two-step approach. In the first step, we select suspected metal-poor ([Fe/H] <–0.5) and α-poor ([Mg/Fe] <0) stars as our targets. In the second step, we determine [Mg/Fe] from low-resolution (R = 2000) stellar spectra for our targets and select stars with [Mg/Fe] <–0.1 as candidate EAP stars. In a sample of 40,000 stars with atmospheric parameters in the range of T{sub eff} = [4500, 7000]more » K, log g = [1.0, 5.0], and [Fe/H] = [–4.0, +0.5], 14 candidate stars were identified. Three of these stars are found to have already been confirmed by other research.« less

Authors:
;  [1]
  1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
Publication Date:
OSTI Identifier:
22364984
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 790; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ATMOSPHERES; COMPARATIVE EVALUATIONS; DATA ANALYSIS; EXCEPTIONS; GALAXIES; IRON; MAGNESIUM; METALLICITY; METALS; RESOLUTION; SATELLITES; SKY; SPECTRA; STARS

Citation Formats

Xing, Q. F., and Zhao, G., E-mail: qfxing@nao.cas.cn, E-mail: gzhao@nao.cas.cn. Mining the Sloan digital sky survey in search of extremely α-poor stars in the galaxy. United States: N. p., 2014. Web. doi:10.1088/0004-637X/790/1/33.
Xing, Q. F., & Zhao, G., E-mail: qfxing@nao.cas.cn, E-mail: gzhao@nao.cas.cn. Mining the Sloan digital sky survey in search of extremely α-poor stars in the galaxy. United States. doi:10.1088/0004-637X/790/1/33.
Xing, Q. F., and Zhao, G., E-mail: qfxing@nao.cas.cn, E-mail: gzhao@nao.cas.cn. Sun . "Mining the Sloan digital sky survey in search of extremely α-poor stars in the galaxy". United States. doi:10.1088/0004-637X/790/1/33.
@article{osti_22364984,
title = {Mining the Sloan digital sky survey in search of extremely α-poor stars in the galaxy},
author = {Xing, Q. F. and Zhao, G., E-mail: qfxing@nao.cas.cn, E-mail: gzhao@nao.cas.cn},
abstractNote = {As we know, the majority of metal-poor Galactic halo stars appear to have chemical abundances that were enhanced by α-elements (e.g., O, Mg, Si, Ca, and Ti) during the early stage of the Galaxy. Observed metal-poor halo stars preserved this pattern by exhibiting abundance ratios [α/Fe] ∼+0.4. A few striking exceptions that show severe departures from the general enhanced α-element chemical abundance trends of the halo have been discovered in recent years. They possess relatively low [α/Fe] compared to other comparable-metallicity stars, with abundance ratios over 0.5 dex lower. These stars may have a different chemical enrichment history from the majority of the halo. Similarly, low-α abundances are also displayed by satellite dwarf spheroidal (dSph) galaxies. We present a method to select extremely α-poor (EAP) stars from the SDSS/SEGUE survey. The method consists of a two-step approach. In the first step, we select suspected metal-poor ([Fe/H] <–0.5) and α-poor ([Mg/Fe] <0) stars as our targets. In the second step, we determine [Mg/Fe] from low-resolution (R = 2000) stellar spectra for our targets and select stars with [Mg/Fe] <–0.1 as candidate EAP stars. In a sample of 40,000 stars with atmospheric parameters in the range of T{sub eff} = [4500, 7000] K, log g = [1.0, 5.0], and [Fe/H] = [–4.0, +0.5], 14 candidate stars were identified. Three of these stars are found to have already been confirmed by other research.},
doi = {10.1088/0004-637X/790/1/33},
journal = {Astrophysical Journal},
number = 1,
volume = 790,
place = {United States},
year = {Sun Jul 20 00:00:00 EDT 2014},
month = {Sun Jul 20 00:00:00 EDT 2014}
}