Probing the Interstellar Medium near Star-forming Regions with Gamma-Ray Burst Afterglow Spectroscopy: Gas, Metals, and Dust

By J. Xavier Prochaska, Hsiao-Wen Chen, M. Dessauges-Zavadsky, Joshua S. Bloom. 2007

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We study the chemical abundances of the interstellar medium surrounding high-z gamma-ray bursts (GRBs) through analysis of the damped Lyα systems (DLAs) identified in afterglow spectra. These GRB DLAs are characterized by large H I column densities NH i and metallicities [M/H] spanning 1/100 to nearly solar, with median [M/H] > -1 dex. The majority of GRB DLAs have [M/H] values exceeding the cosmic mean metallicity of atomic gas at z > 2; i.e., if anything, the GRB DLAs are biased to larger metallicity. We also observe (1) large [Zn/Fe] values (>+0.6 dex) and subsolar Ti/Fe ratios, which imply substantial differential depletion; (2) large α/Fe ratios, suggesting nucleosynthetic enrichment by massive stars; and (3) low C0/C+ ratios (<10-4). Quantitatively, the observed depletion levels and C0/C+ ratios of the gas are not characteristic of cold, dense H I clouds in the Galactic interstellar medium (ISM). We argue that the GRB DLA represents the ISM near the GRB but not gas directly local to the GRB (e.g., its molecular cloud or circumstellar material). We compare these observations with DLAs intervening in background quasars (QSO DLAs). The GRB DLAs exhibit larger N values, higher α/Fe and Zn/Fe ratios, and higher metallicity than the QSO DLAs. Although these differences are statistically significant, the offsets are relatively modest (N excepted). We argue that the differences result primarily from galactocentric radius-dependent differences in the ISM: GRB DLAs preferentially probe denser, more depleted, higher metallicity gas located in the inner few kiloparsecs, whereas QSO DLAs are more likely to intersect the less dense, less enriched, outer regions of the galaxy. Finally, we investigate whether dust obscuration may exclude GRB DLA sight lines from QSO DLA samples; we find that the majority of GRB DLAs would be recovered, which implies little observational bias against large N systems.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ce021338a6e0a4dad241733bbe62010a76e9a2e3

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Citations in the corpus

De re metallica: the cosmic chemical evolution of galaxies (2018, background): “…relative (and often absolute) chemical abundances (e.g., Prochaska & Wolfe, 1999; Berg et al., 2015a; Fumagalli, 2014; Pettini et al., 2008; Henry & Prochaska, 2007; Dessauges-Zavadsky et al., 2006; Wolfe et al., 2005; Prochaska et al., 2003a; Rafelski et al., 2012; Neeleman et al., 2013;…”
GRB 080913 AT REDSHIFT 6.7 (2008, background): “…et al. 1998; Chary et al. 2007; Yüksel et al. 2008), re-ionization of the intergalactic medium (Miralda-Escude 1998, Totani et al. 2006), and the metal enrichment history of the Universe (e.g. Hartmann et al. 2004; Fynbo et al. 2006; Savaglio 2006; Berger et al. 2006; Prochaska et al. 2007).”
THE FIRST POSITIVE DETECTION OF MOLECULAR GAS IN A GRB HOST GALAXY (2009, background): “8 Las Cumbres Observatory, 6740 Cortona Dr. Suite 102, Santa Barbara, CA 93117. son et al. 2006), metal-enriched material (Savaglio et al. 2003), and large depletion factors indicating significant dust formation (e.g., Watson et al. 2006; Prochaska et al. 2007).”
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies (2014, methodology): “This method has been used successfully with GRBs (e.g. Prochaska et al. 2007; Ledoux et al. 2009).”
GRB hosts through cosmic time - VLT/X-Shooter emission-line spectroscopy of 96 γ-ray-burst-selected galaxies at 0.1 (2015, background): “…metallicity can be probed directly and accurately in absorption at z > 1.8 through their DLAs (e.g., Vreeswijk et al. 2004; Savaglio 2006; Prochaska et al. 2007; Ledoux et al. 2009), for faint (GRB-selected) galaxies it is unavoidable to resort to diagnostic ratios of strong emission…”
Galaxies with Wolf-Rayet signatures in the low-redshift Universe. A survey using the Sloan Digital Sky Survey (2008, background): “Since cosmological GRBs appear to originate in low metallicity hosts (e.g. Prochaska et al. 2007) and potentially from Wolf-Rayet progenitors, resolving this issue is of major importance not only from the point of view of WolfRayet star formation but also to understand the possible progenitor…”
A UNIFIED REPRESENTATION OF GAS-PHASE ELEMENT DEPLETIONS IN THE INTERSTELLAR MEDIUM (2009, background): “…Prochaska, Howk, & Wolfe 2003; Dessauges-Zavadsky et al. 2004; Wolfe, Gawiser, & Prochaska 2005), as well as gases within or in front of the host galaxies of gamma-ray burst (GRB) sources that had bright afterglows in the visible part of the spectrum (Prochaska et al. 2007; Calura et al. 2009).”
The Destruction of Cosmological Minihalos by Primordial Supernovae (2008, background): “If Population III stars are rapidly rotating, they may explode as gamma ray bursts (Bromm & Loeb 2006) and could be used to probe the interstellar medium of the halos in which they form, as has been done in the z < 4 universe (Chen et al. 2005; Prochaska et al. 2006, 2007).”
UV CONTINUUM SLOPE AND DUST OBSCURATION FROM z ∼ 6 TO z ∼ 2: THE STAR FORMATION RATE DENSITY AT HIGH REDSHIFT (2009, background): “…in the high redshift universe (e.g., Yüksel et al. 2008; Li 2008; Kistler et al. 2009) and may not be biased to lower metallicity environments (Prochaska et al. 2007), we would expect GRBs to occur in galaxies roughly in proportion to their share of the star formation activity in the high…”
FORMATION OF THE FIRST NUCLEAR CLUSTERS AND MASSIVE BLACK HOLES AT HIGH REDSHIFT (2008, methodology): “The cosmic metallicity history (MEH) has been investigated both from an observational and a theoretical prospective (Scannapieco et al. 2003, Tornatore et al. 2006, Savaglio 2006, Savaglio et al. 2005, Prochaska et al. 2003, Prochaska et al. 2007, Kulkarni et al. 2005, Li 2007).”