Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 451, Issue 1, Pages 167-183Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stv960
Keywords
gamma-ray burst: individual: GRB 121024A; galaxies: abundances
Categories
Funding
- University of Iceland Research fund
- Weizmann Institute of Science Dean of Physics Fellowship
- Koshland Center for Basic Research
- DNRF
- Royal Society Dorothy Hodgkin Fellowship
- ERC-StG grant [EGGS-278202]
- Ramon y Cajal fellowship
- Spanish research project [AYA2012-39362-C02-02]
- European Commission [FP7-PEOPLE-2012-CIG 322307]
- CONICYT-Chile FONDECYT [3140534]
- Basal-CATA [PFB-06/2007]
- 'Millennium Institute of Astrophysics (MAS)' of Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo [IC120009]
- Leibniz-Prize (DFG grant) [HA 1850/28-1]
- Science and Technology Facilities Council [ST/K001000/1] Funding Source: researchfish
- STFC [ST/K001000/1, ST/H001972/1] Funding Source: UKRI
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1211782] Funding Source: National Science Foundation
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We present the first reported case of the simultaneous metallicity determination of a gamma- ray burst (GRB) host galaxy, from both afterglow absorption lines as well as strong emission- line diagnostics. Using spectroscopic and imaging observations of the afterglow and host of the long- duration Swift GRB 121024A at z = 2.30, we give one of the most complete views of a GRB host/ environment to date. We observe a strong damped Lya absorber (DLA) with a hydrogen column density of log N(H i) = 21.88 +/- 0.10, H-2 absorption in the Lyman- Werner bands (molecular fraction of log(f) approximate to- 1.4; fourth solid detection of molecular hydrogen in a GRB- DLA), the nebular emission lines H alpha, H beta, [OII], [O III] and [N II], as well as metal absorption lines. We find aGRB host galaxy that is highly star forming (SFR similar to 40M circle dot yr(-1)), with a dust- corrected metallicity along the line of sight of [Zn/ H](corr) =- 0.6 +/- 0.2 ([O/H]similar to- 0.3 from emission lines), and a depletion factor [Zn/ Fe] = 0.85 +/- 0.04. The molecular gas is separated by 400 km s(-1) (and 1-3 kpc) from the gas that is photoexcited by the GRB. This implies a fairly massive host, in agreement with the derived stellar mass of log(M*/M-circle dot) = 9.9(-0.3)(+0.2). We dissect the host galaxy by characterizing its molecular component, the excited gas, and the line- emitting star- forming regions. The extinction curve for the line of sight is found to be unusually flat (R-V similar to 15). We discuss the possibility of an anomalous grain size distributions. We furthermore discuss the different metallicity determinations from both absorption and emission lines, which gives consistent results for the line of sight to GRB 121024A.
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