The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime★
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In this paper, a high spectral resolution survey of the most metal-poor damped Lyα absorption systems (DLAs) aimed at probing the nature and nucleosynthesis of the earliest generations of stars is presented.Abstract:
We present a high spectral resolution survey of the most metal-poor damped Lyα absorption systems (DLAs) aimed at probing the nature and nucleosynthesis of the earliest generations of stars. Our survey comprises 22 systems with iron abundance less than 1/100 solar; observations of seven of these are reported here for the first time. Together with recent measures of the abundances of C and O in Galactic metal-poor stars, we reinvestigate the trend of C/O in the very metal-poor (VMP) regime and we compare, for the first time, the O/Fe ratios in the most metal-poor DLAs and in halo stars. We confirm the near-solar values of C/O in DLAs at the lowest metallicities probed, and find that their distribution is in agreement with that seen in Galactic halo stars. We find that the O/Fe ratio in VMP DLAs is essentially constant, and shows very little dispersion, with a mean [〈O/Fe〉]=+0.39 ± 0.12, in good agreement with the values measured in Galactic halo stars when the oxygen abundance is measured from the [O i] λ6300 line. We speculate that such good agreement in the observed abundance trends points to a universal origin for these metals. In view of this agreement, we construct the abundance pattern for a typical VMP DLA and compare it to model calculations of Population II and Population III nucleosynthesis to determine the origin of the metals in VMP DLAs. Our results suggest that the most metal-poor DLAs may have been enriched by a generation of metal-free stars; however, given that abundance measurements are currently available for only a few elements, we cannot yet rule out an additional contribution from Population II stars.read more
Citations
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Journal ArticleDOI
A search for stars of very low metal abundance. vi. detailed abundances of 313 metal-poor stars*
Ian U. Roederer,George W. Preston,Ian B. Thompson,Stephen A. Shectman,Christopher Sneden,Gregory S. Burley,Daniel D. Kelson +6 more
TL;DR: In this article, the authors presented radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars.
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Near-Field Cosmology with Extremely Metal-Poor Stars
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TL;DR: The most metal-poor stars in the Galactic halo and satellite dwarf galaxies provide an opportunity to explore the chemical and physical conditions of the earliest star-forming environments in the Universe.
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Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six
TL;DR: In this article, the authors report the discovery of an extremely long (∼110 Mpc/h) and dark (τeff≳7) Lyα trough extending down to z≃5.5 towards the zem≃6.0 quasar ULAS J0148+0600.
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METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5
TL;DR: In this article, chemical abundance measurements for 47 damped Lyα (DLA) systems, 30 at z > 4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes are presented.
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Precision measures of the primordial abundance of deuterium
TL;DR: In this article, the primordial abundance of deuterium was measured in the very metal-poor (Fe/H] = 2.06726 toward the QSO SDSS J1358+6522.
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