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Are long gamma-ray bursts biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of bright LGRBs: II. Star formation rates and metallicities at z < 1

Japelj, J and Vergani, SD and Salvaterra, R and D'Avanzo, P and Mannucci, F and Fernandez-Soto, A and Boissier, S and Hunt, LK and Atek, H and Rodríguez-Muñoz, L and Scodeggio, M and Cristiani, S and Le Floc'h, E and Flores, H and Gallego, J and Ghirlanda, G and Gomboc, A and Hammer, F and Perley, DA and Pescalli, A and Petitjean, P and Puech, M and Rafelski, M and Tagliaferri, G (2016) Are long gamma-ray bursts biased tracers of star formation? Clues from the host galaxies of the Swift/BAT6 complete sample of bright LGRBs: II. Star formation rates and metallicities at z < 1. Astronomy & Astrophysics, 590. ISSN 1432-0746

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Abstract

Aims. Long gamma-ray bursts (LGRBs) are associated with the deaths of massive stars and might therefore be a potentially powerful tool for tracing cosmic star formation. However, especially at low redshifts (z < 1.5) LGRBs seem to prefer particular types of environment. Our aim is to study the host galaxies of a complete sample of bright LGRBs to investigate the effect of the environment on GRB formation. Methods. We studied host galaxy spectra of the Swift/BAT6 complete sample of 14 z < 1 bright LGRBs. We used the detected nebular emission lines to measure the dust extinction, star formation rate (SFR), and nebular metallicity (Z) of the hosts and supplemented the data set with previously measured stellar masses M∗. The distributions of the obtained properties and their interrelations (e.g. mass-metallicity and SFR-M∗ relations) are compared to samples of field star-forming galaxies. Results. We find that LGRB hosts at z < 1 have on average lower SFRs than if they were direct star formation tracers. By directly comparing metallicity distributions of LGRB hosts and star-forming galaxies, we find a good match between the two populations up to 12 + log (O/H) ∼ 8.4-8.5, after which the paucity of metal-rich LGRB hosts becomes apparent. The LGRB host galaxies of our complete sample are consistent with the mass-metallicity relation at similar mean redshift and stellar masses. The cutoff against high metallicities (and high masses) can explain the low SFR values of LGRB hosts. We find a hint of an increased incidence of starburst galaxies in the Swift/BAT6 z < 1 sample with respect to that of a field star-forming population. Given that the SFRs are low on average, the latter is ascribed to low stellar masses. Nevertheless, the limits on the completeness and metallicity availability of current surveys, coupled with the limited number of LGRB host galaxies, prevents us from investigating more quantitatively whether the starburst incidence is such as expected after taking into account the high-metallicity aversion of LGRB host galaxies. © 2016 ESO.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
Date Deposited: 21 Feb 2017 08:45
Last Modified: 10 Sep 2017 16:37
DOI or Identification number: 10.1051/0004-6361/201628314
URI: http://researchonline.ljmu.ac.uk/id/eprint/5613

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