C, N, O abundances in the most metal-poor damped Lyman alpha systems★

By M. Pettini, B. Zych, C. Steidel, F. Chaffee. 2007

142 citations recorded by the source corpus.

This study focuses on some of the most metal-poor damped Lyα (DLA) absorbers known in the spectra of high-redshift QSOs, using new and archival observations obtained with ultraviolet-sensitive echelle spectrographs on the Keck and VLT telescopes. The weakness and simple velocity structure of the absorption lines in these systems allow us to measure the abundances of several elements, and in particular those of C, N and O, a group that is difficult to study in DLAs of more typical metallicities. We find that when the oxygen abundance is less than ∼1/100 of solar, the C/O ratio in high-redshift DLAs and sub-DLAs matches that of halo stars of similar metallicity and shows higher values than expected from galactic chemical evolution models based on conventional stellar yields. Furthermore, there are indications that at these low metallicities the N/O ratio may also be above simple expectations and may exhibit a minimum value, as proposed by Centurion and her collaborators in 2003. Both results can be interpreted as evidence for enhanced production of C and N by massive stars in the first few episodes of star formation, in our Galaxy and in the distant protogalaxies seen as QSO absorbers. The higher stellar yields implied may have an origin in stellar rotation which promotes mixing in the stars' interiors, as considered in some recent model calculations. We briefly discuss the relevance of these results to current ideas on the origin of metals in the intergalactic medium and the universality of the stellar initial mass function.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2664e1c5f240e0cfd47be6748bcd798ccf63b17f

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In Astronomy and Astrophysics

1. C. Steidel
2. Naveen A. Reddy
3. M. Pettini
4. A. Shapley
5. D. Erb
6. D. Law
7. G. Rudie
8. R. Dav'e

Citations in the corpus

• PHYSICAL CONDITIONS IN A YOUNG, UNREDDENED, LOW-METALLICITY GALAXY AT HIGH REDSHIFT (2010, background): “This effect has been seen in the lensed z = 2.7 galaxy MS1512-cB58, in which N is underabundant with respect to O by a factor of ∼ 3 (Pettini et al. 2002), as well as in local galaxies and in damped Lyα systems (Pettini et al. 2008).”
• METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5 (2012, unknown): “In addition, we avoid samples with metallicity biases, such as metal poor samples (e.g. Pettini et al. 2008; Penprase et al. 2010; Cooke etal.”
• STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, background): “…evidence for the low values of log(N/O) (' −1.5) that might be expected for very young systems in which only primary N has enriched the ISM, such as damped Lyman α systems (see e.g., Pettini et al. 2008), nor of a strong dependence of (N/O) on (O/H) as expected as secondary N production progresses.”
• A new, precise measurement of the primordial abundance of deuterium (2012, background): “…background radiation (CMB), light element abundances can improve constraints on cosmological parameters, primarily the spectral index of primordial fluctuations (Pettini et al. 2008), and on the effective number of light fermion species, Neff (e.g. Simha & Steigman 2008; Nollett & Holder 2011).”
• THE BIMODAL METALLICITY DISTRIBUTION OF THE COOL CIRCUMGALACTIC MEDIUM AT z ≲ 1 (2013, unknown): “There are 29 LLS (28 H I-selected, 1 Mg II-selected), 29 SLLS, and 26 DLAs.”
• Deuterium abundance in the most metal-poor damped Lyman alpha system: converging on Ωb,0h2 (2008, background): “The most metal-poor DLAs remain a fertile ground for studying early episodes of stellar nucleosynthesis (e.g. Pettini et al. 2008), and it is certainly worthwhile continuing to be aware of their potential for further refinements of (D/H)p. AC K N OW L E D G M E N T S The work presented in this…”
• A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, background): “This is supported by α-element abundances measured in high redshift Damped Lyman-α systems (Molaro et al. 2001; Pettini et al. 2008) and in absorption systems along quasar sight lines (Becker et al. 2006), both of which are consistent with yields expected from a Salpeter IMF at the high mass end.”
• The most metal-poor damped Lyα systems: insights into chemical evolution in the very metal-poor regime★ (2011, methodology): “In this contribution, we build on our ongoing survey for the most metal-poor DLAs as probes of early nucleosynthesis (Pettini et al. 2008; Cooke et al. 2011).”