Cold gas in the early Universe - Survey for neutral atomic-carbon in GRB host galaxies at 1 < z< 6 from optical afterglow spectroscopy

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review



  • Author: Heintz, K. E.

    University of Copenhagen, Denmark

  • Author: Ledoux, C.

    European Southern Observatory, Chile

  • Author: Fynbo, J. P. U.

    University of Copenhagen, Denmark

  • Author: Jakobsson, P.

    University of Iceland, Iceland

  • Author: Noterdaeme, P.

    CNRS, France

  • Author: Krogager, J.-K.

    CNRS, France

  • Author: Bolmer, J.

    European Southern Observatory, Chile

  • Author: Møller, P.

    European Southern Observatory, Germany

  • Author: Vergani, S. D.

    PSL Research University, France

  • Author: Watson, D.

    University of Copenhagen, Denmark

  • Author: Zafar, T.

    Australian Astronomical Observatory, Australia

  • Author: De Cia, A.

    European Southern Observatory, Germany

  • Author: Tanvir, N. R.

    University of Leicester, United Kingdom

  • Author: Malesani, D. B.

    National Space Institute, Technical University of Denmark, Elektrovej, building 327+328 ; Ørsted Plads, building 348 ; Richard Petersens Plads, building 305, DK-2800, Kgs. Lyngby, Denmark

  • Author: Japelj, J.

    University of Amsterdam, Netherlands

  • Author: Covino, S.

    National Institute for Astrophysics, Italy

  • Author: Kaper, L.

    University of Amsterdam, Netherlands

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We present a survey for neutral atomic-carbon (C I) along gamma-ray burst (GRB) sightlines, which probes the shielded neutral gas-phase 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 C I 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 C I 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 C I 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 C I 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.
Original languageEnglish
Article numberA20
JournalAstronomy & Astrophysics
Number of pages13
Publication statusPublished - 2019
CitationsWeb of Science® Times Cited: No match on DOI

    Research areas

  • Gamma-ray burst: general, Galaxies: ISM, Galaxies: high-redshift, Dust, Extinction

ID: 165471389