2010/06/21 by Bryan E. Penprase, Penprase, Bryan E., J. X. Prochaska +9
Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Doppler effect #Emission spectrum #Equivalent width #Galaxies: Formation, Evolution, Phenomena #Galaxy #Lambda #Metallicity #Optics #Physics #Quasar #Redshift #Saturation (graph theory) #Spectral line #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.48550/arxiv.1006.4119
Accepted for publication in the Astrophysical Journal, June 16, 2010
arxiv created 2010/06/21 · openalex publication_date 2010/06/21 · arxiv updated 2010/06/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present the first results from a survey of SDSS quasars selected for strong H I damped Lyman-α (DLA) absorption with corresponding low equivalent width absorption from strong low-ion transitions (e.g. C II λ1334 and Si II λ1260). These metal-poor DLA candidates were selected from the SDSS DR5 quasar spectroscopic database, and comprise a large new sample for probing low metallicity galaxies. Medium-resolution echellette spectra from the Keck ESI spectrograph for an initial sample of 35 systems were obtained to explore the metal-poor tail of the DLA distribution and to investigate the nucleosynthetic patterns at these metallicities. We have estimated saturation corrections for the moderately under-resolved spectra, and systems with very narrow Doppler parameter (b ≤ 5 km s-1) will likely have underestimated abundances. For those systems with Doppler parameters b > 5 km s-1, we have measured low metallicity DLA gas with [X/H] < -2.4 for at least one of C, O, Si, or Fe. Assuming non-saturated components, we estimate that several DLA systems have [X/H] < -2.8, including five DLA systems with both low equivalent widths and low metallicity in transitions of both C II and O I. All of the measured DLA metallicities, however, exceed or are consistent with a metallicity of at least 1/1000 of solar, regardless of the effects of saturation in our spectra. Our results indicate that the metal-poor tail of galaxies at z ∼ 3 drops exponentially at [X/H]< -3. The observed ratio of [C/O] for values of [O/H] < -2.5 exceeds values seen in moderate metallicity DLA systems, and also exceeds theoretical nucleosynthesis predictions for higher mass Population III stars.