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Title: Cold gas in the early Universe Survey for neutral atomic-carbon in GRB host galaxies at 1 < z < 6 from optical afterglow spectroscopy
Authors: Heintz, KE
Ledoux, C
Fynbo, JPU
Jakobsson, P
Noterdaeme, P
Krogager, J-K
Bolmer, J
Moller, P
Vergani, SD
Watson, D
Zafar, T
De Cia, A
Tanvir, NR
Malesani, DB
Japelj, J
Covino, S
Kaper, L
First Published: 20-Dec-2018
Publisher: EDP Sciences for European Southern Observatory (ESO)
Citation: ASTRONOMY & ASTROPHYSICS, 2019, 621, A20
Abstract: We present a survey for neutral atomic-carbon (C i) along gamma-ray burst (GRB) sightlines, which probes the shielded neutral gasphase in the interstellar medium (ISM) of GRB host galaxies at high redshift. We compile a sample of 29 medium- to high-resolution GRB optical afterglow spectra spanning a redshift range through most of cosmic time from 1 < z < 6. We find that seven (≈25%) of the GRBs entering our statistical sample have Ci detected in absorption. It is evident that there is a strong excess of cold gas in GRB hosts compared to absorbers in quasar sightlines. We investigate the dust properties of the GRB Ci absorbers and find that the amount of neutral carbon is positively correlated with the visual extinction, AV, and the strength of the 2175 Å dust extinction feature, Abump. GRBs with Ci detected in absorption are all observed above a certain threshold of logN(H i)/cm−2 + [X/H] > 20.7 and a dust-phase iron column density of logN(Fe)dust/cm−2 > 16.2. In contrast to the SED-derived dust properties, the strength of the C i absorption does not correlate with the depletion-derived dust properties. This indicates that the GRB C i absorbers trace dusty systems where the dust composition is dominated by carbon-rich dust grains. The observed higher metal and dust column densities of the GRB Ci absorbers compared to H2- and C i-bearing quasar absorbers is mainly a consequence of how the two absorber populations are selected, but is also required in the presence of intense UV radiation fields in actively star-forming galaxies.
DOI Link: 10.1051/0004-6361/201834246
ISSN: 1432-0746
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2018, EDP Sciences for European Southern Observatory (ESO). Deposited with reference to the publisher’s open access archiving policy. (
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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