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Title: | GRB hosts through cosmic time. VLT/X-Shooter emission-line spectroscopy of 96 γ-ray-burst-selected galaxies at 0.1 <z < 3.6 | Authors: | Krühler, T. Malesani, D. Fynbo, J. P. U. Hartoog, O. E. Hjorth, J. Jakobsson, P. Perley, D. A. ROSSI, Andrea Schady, P. Schulze, S. Tanvir, N. R. Vergani, S. D. Wiersema, K. Afonso, P. M. J. Bolmer, J. Cano, Z. COVINO, Stefano D'Elia, V. de Ugarte Postigo, A. Filgas, R. Friis, M. Graham, J. F. Greiner, J. Goldoni, P. Gomboc, A. Hammer, F. Japelj, J. Kann, D. A. Kaper, L. Klose, S. Levan, A. J. Leloudas, G. Milvang-Jensen, B. Nicuesa Guelbenzu, A. PALAZZI, ELIANA PIAN, Elena PIRANOMONTE, Silvia Sánchez-Ramírez, R. Savaglio, S. Selsing, J. TAGLIAFERRI, Gianpiero Vreeswijk, P. M. Watson, D. J. Xu, D. |
Issue Date: | 2015 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 581 | First Page: | A125 | Abstract: | We present data and initial results from VLT/X-Shooter emission-line spectroscopy of 96 galaxies selected by long γ-ray bursts (GRBs) at 0.1 <z< 3.6, the largest sample of GRB host spectra available to date. Most of our GRBs were detected by Swift and 76% are at 0.5 <z< 2.5 with a median z<SUB>med</SUB> ~ 1.6. Based on Balmer and/or forbidden lines of oxygen, nitrogen, and neon, we measure systemic redshifts, star formation rates (SFR), visual attenuations (A<SUB>V</SUB>), oxygen abundances (12 + log (O/H)), and emission-line widths (σ). We study GRB hosts up to z ~ 3.5 and find a strong change in their typical physical properties with redshift. The median SFR of our GRB hosts increases from SFR<SUB>med</SUB> ~ 0.6 M<SUB>☉</SUB> yr<SUP>-1</SUP> at z ~ 0.6 up to SFR<SUB>med</SUB> ~ 15 M<SUB>☉</SUB> yr<SUP>-1</SUP> at z ~ 2. A higher ratio of [O iii]/[O ii] at higher redshifts leads to an increasing distance of GRB-selected galaxies to the locus of local galaxies in the Baldwin-Phillips-Terlevich diagram. There is weak evidence for a redshift evolution in A<SUB>V</SUB> and σ, with the highest values seen at z ~ 1.5 (A<SUB>V</SUB>) or z ~ 2 (σ). Oxygen abundances of the galaxies are distributed between 12 + log (O/H) = 7.9 and 12 + log (O/H) = 9.0 with a median 12 + log (O/H)<SUB>med</SUB> ~ 8.5. The fraction of GRB-selected galaxies with super-solar metallicities is ~20% at z< 1 in the adopted metallicity scale. This is significantly less than the fraction of total star formation in similar galaxies, illustrating that GRBs are scarce in high metallicity environments. At z ~ 3, sensitivity limits us to probing only the most luminous GRB hosts for which we derive metallicities of Z ≲ 0.5 Z<SUB>☉</SUB>. Together with a high incidence of Z ~ 0.5 Z<SUB>☉</SUB> galaxies at z ~ 1.5, this indicates that a metallicity dependence at low redshift will not be dominant at z ~ 3. Significant correlations exist between the hosts' physical properties. Oxygen abundance, for example, relates to A<SUB>V</SUB> (12 + log (O/H) ∝ 0.17·A<SUB>V</SUB>), line width (12 + log (O/H) ∝ σ<SUP>0.6</SUP>), and SFR (12 + log (O/H) ∝ SFR<SUP>0.2</SUP>). In the last two cases, the normalization of the relations shift to lower metallicities at z> 2 by ~0.4 dex. These properties of GRB hosts and their evolution with redshift can be understood in a cosmological context of star-forming galaxies and a picture in which the hosts' properties at low redshift are influenced by the tendency of GRBs to avoid the most metal-rich environments. <P />Based on observations at ESO, Program IDs: 084.A-0260, 084.A-0303, 085.A-0009, 086.B-0954, 086.A-0533, 086.A-0874, 087.A-0055, 087.A-0451, 087.B-0737, 088.A-0051, 088.A-0644, 089.A-0067, 089.A-0120, 089.D-0256, 089.A-0868, 090.A-0088, 090.A-0760, 090.A-0825, 091.A-0342, 091.A-0703, 091.A-0877, 091.C-0934, 092.A-0076, 092.A-0124, 092.A-0231, 093.A-0069, 094.A-0593.Tables 1-4 and appendices are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201425561/olm">http://www.aanda.org</A>The reduced spectra are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A125">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A125 | Acknowledgments: | We are grateful to the referee and the editor, Rubina Kotak, for comments and for providing an extensive and constructive report, which has helped to increase the quality and strength of the manuscript significantly. We thank the Swift team for building and operating such an excellent facility. We also acknowledge the astronomical and technical support at Paranal observatory without which none of the presented spectra would have been taken. The Dark Cosmology Centre is funded by the Danish National Research Foundation. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013)/ERC Grant agreement No. EGGS-278202. Part of the funding for GROND (both hardware as well as personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. T.K. thanks A. Müller, L. Guzman, and L. Watson for providing the vibrant scientific atmosphere in Vitacura where some of this work was carried out. D.M. acknowledges the Instrument center for Danish astrophysics (IDA) for support. S.Sch. acknowledges support from CONICYT-Chile FONDECYT 3140534, Basal- CATA PFB-06/2007, and Project IC120009 ”Millennium Institute of Astrophysics (MAS)” of Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo. A.R. acknowledges support from PRIN-INAF 2012/13. Support for DAP was provided by NASA through Hubble Fellowship grant HST-HF-51296.01-A awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., for NASA, under contract NAS 5-26555, and by an award issued by JPL/Caltech. E.P. acknowledges support from grants ASI-INAF I/088/06/0 and PRIN INAF 2011. P.S. acknowledges support through the Sofja Kovalevskaja Award from the Alexander von Humboldt Foundation of Germany. J.F.G. acknowledges support through the Sofja Kovalevskaja Award to P. Schady from the Alexander von Humboldt Foundation of Germany. S.K. and A.N.G. acknowledge support by DFG grant Kl 766/16-1. S.Sav. acknowledges support from the Bundesministerium für Wirtschaft and Technologie through DLR (Deutsches Zentrum für Luft- und Raumfahrt e.V.) FKZ 50 OR 1211. Based in part on observations collected with the 2.2 m MPG telescope on La Silla as part of the program CN2014B-102. | URI: | http://hdl.handle.net/20.500.12386/23740 | URL: | https://www.aanda.org/articles/aa/abs/2015/09/aa25561-14/aa25561-14.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201425561 | Bibcode ADS: | 2015A&A...581A.125K | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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