Volume 607, November 2017
|Number of page(s)||18|
|Published online||22 November 2017|
Gas inflow and outflow in an interacting high-redshift galaxy
The remarkable host environment of GRB 080810 at z = 3.35⋆
1 Max-Planck-Institute für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
2 Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
3 Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064, USA
4 Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
5 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
Received: 28 April 2017
Accepted: 13 July 2017
We reveal multiple components of an interacting galaxy system at z ≈ 3.35 through a detailed analysis of the exquisite high-resolution Keck/HIRES spectrum of the afterglow of a gamma-ray burst (GRB). Through Voigt-profile fitting of absorption lines from the Lyman series, we constrain the neutral hydrogen column density to NH i ≤ 1018.35 cm-2 for the densest of four distinct systems at the host redshift of GRB 080810, which is among the lowest NH i ever observed in a GRB host, even though the line of sight passes within a projected 5 kpc of the galaxy centres. By detailed analysis of the corresponding metal absorption lines, we derive chemical, ionic, and kinematic properties of the individual absorbing systems, and thus build a picture of the host as a whole. Striking differences between the systems imply that the line of sight passes through several phases of gas: the star-forming regions of the GRB host; enriched material in the form of a galactic outflow; the hot and ionised halo of a second interacting galaxy falling towards the host at a line-of-sight velocity of 700 km s-1; and a cool metal-poor cloud that may represent one of the best candidates yet for the inflow of metal-poor gas from the intergalactic medium.
Key words: galaxies: evolution / galaxies: interactions / gamma-ray burst: individual: 080810
The reduced spectrum is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A107
© ESO, 2017
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