The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime★

By R. Cooke, M. Pettini, C. Steidel, G. Rudie, P. Nissen. 2011

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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.

Subfields: Molecular Biology, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/855b3d91a379240d0095dbae0bafe31d03d3f683

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Citations in the corpus

A new, precise measurement of the primordial abundance of deuterium (2012, methodology): “Typical metallicities at redshifts z = 2–4 are ZDLA ≃ 1/10–1/100Z⊙ (Ellison et al. 2012), but with a tail that extends to ZDLA < 1/1000Z⊙ (Penprase et al. 2010; Cooke et al. 2011).”
Star formation sustained by gas accretion (2014, background): “From 0 < z < 5, the relationship has a slope of -0.2 dex per unit z, a large scatter (±1 dex at a given z), and a lower limit that extends at least to Z /3000 (Rafelski et al. 2012, 2014; Cooke et al. 2011b).”
THE MOST METAL-POOR STARS. IV. THE TWO POPULATIONS WITH [Fe/H] ≲ −3.0 (2012, background): “Becker et al. (201) supplement their new results with those of others at lower redshift (including those of Cooke et al. 2011b, except for their system having the composition of a CEMP star) to provide a sample over the redshift rangez = 2 – 6.”
A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, background): “Observations of the high redshift Universe reveal carbon, magnesium, and other metals in the clouds of hydrogen that fueled the rising star formation rate density during the first several Gyr after the Big Bang (e.g., Sargent et al. 1988; Cooke et al. 2011; Matejek & Simcoe 2012).”
THE MASS SPECTRUM OF THE FIRST STARS (2014, background): “(A color version of this figure is available in the online journal.) patterns of the extremely metal-poor stars with [Fe/H] ∼ −3 (BD –18:5550, CS 29502–042, CS 29516–024, and CS 31082–001, Cayrel et al. 2004)10 and DLA systems (Cooke et al. 2011).”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, methodology): “Of particular interest, in the present context, is the result that one (J0035–0918) of the 10 systems having both C and Fe abundances has the composition of a CEMP-no star ([Fe/H] = −3.0 and [C/Fe] = +1.5) (see also Cooke et al. 2011a).”
CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES (2014, background): “…characterization of these populations, it will become possible to compare the occurrence rate of CEMP-no stars with the recently discovered carbonenhanced damped Lyα systems (Cooke et al. 2011, 2012) which carry abundance patterns that resemble those from massive, carbon-producing first stars.”
METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5 (2012, background): “On the other hand, recent studies of metal-poor DLAs suggests that their [C/O] distribution is in good agreement with metal-poor halo stars (Penprase et al. 2010; Cooke et al. 2011).”
Ultraviolet emission lines in young low-mass galaxies at z ≃ 2: physical properties and implications for studies at z > 7 (2014, background): “…Fabbian et al. 2009), nearby HII regions (e.g., Garnett et al. 1995, 1997; Kobulnicky & Skillman 1998, Garnett et al. 1999 ), damped Lyα emitters (Cooke et al. 2011), and high redshift galaxies (Shapley et al. 2003, Erb et al. 2010) demonstrate that the C/O ratio increases with increasing O/H…”
CARBON-ENHANCED METAL-POOR STARS IN SDSS/SEGUE. I. CARBON ABUNDANCE ESTIMATION AND FREQUENCY OF CEMP STARS (2013, background): “Other evidence for the large production of carbon at early times comes from the discovery by Cooke et al. (2011) of an extremely metal-poor (EMP; [Fe/H]∼ 3.0) damped Ly-α (DLA) system atz = 2.3 that exhibits enhanced a carbon abundance ratio ([C/Fe]=+1.5) and other elemental-abundance signatures…”
Modelling the nebular emission from primeval to present-day star-forming galaxies (2016, background): “This feature should be particularly useful to investigate the early chemical evolution of galaxies with non-solar carbon-to-oxygen abundance ratios (e.g., Erb et al. 2010; Cooke et al. 2011; see also Garnett et al. 1999).”