Issue |
A&A
Volume 590, June 2016
|
|
---|---|---|
Article Number | A129 | |
Number of page(s) | 15 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201628314 | |
Published online | 30 May 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⋆,⋆⋆
1
INAF–Osservatorio Astronomico di Trieste, via G. B. Tiepolo
11
34131
Trieste
Italy
e-mail: japelj@oats.inaf.it
2
Faculty of Mathematics and Physics, University of
Ljubljana, Jadranska ulica
19, 1000
Ljubljana,
Slovenia
3
GEPI–Observatoire de Paris Meudon. 5 place Jules
Jannsen, 92195
Meudon,
France
4
INAF–Osservatorio Astronomico di Brera, via E. Bianchi
46, 23807
Merate,
Italy
5
Institut d’Astrophysique de Paris, Université Paris 6-CNRS,
UMR7095, 98bis boulevard
Arago, 75014
Paris,
France
6
INAF–IASF Milano, via E. Bassini 15, 20133
Milano,
Italy
7
INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi
5, 50125
Firenze,
Italy
8
Instituto de Física de Cantabria (CSIC-UC),
39005
Santander,
Spain
9
Unidad Asociada Observatori Astronómic (IFCA – Universitat de
Valéncia), Valencia,
Spain
10
Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique
de Marseille) UMR 7326, 13388
Marseille,
France
11
Laboratoire d’Astrophysique, École Polytechnique Fédérale de
Lausanne, Observatoire de Sauverny, 1290
Versoix,
Switzerland
12
Department of Astronomy, Yale University,
260 Whitney Avenue,
New Haven, CT
06511,
USA
13
Departamento de Astrofísica y Ciencias de la Atmósfera,
Universidad Complutense de Madrid, 28040
Madrid,
Spain
14
Dipartimento di Fisica e Astronomia “G. Galilei”, Università di
Padova, Vicolo dell’Osservatorio
3, 35122
Padova,
Italy
15
Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – CNRS –
Université Paris Diderot, Bât. 709, CEA-Saclay, 91191
Gif-sur-Yvette Cedex,
France
16
Faculty of Sciences, University of Nova Gorica,
Vipavska cesta 11c,
5270
Ajdovščina,
Slovenia
17
Dark Cosmology Centre, Niels Bohr Institute, University of
Copenhagen, Juliane Maries Vej
30, 2100
Copenhagen,
Denmark
18
NASA Postdoctoral Program Fellow, Goddard Space Flight
Center, Greenbelt,
MD
20771,
USA
Received: 15 February 2016
Accepted: 4 April 2016
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 ~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.
Key words: gamma-ray burst: general / galaxies: star formation
© ESO, 2016
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