%0 Journal Article %T Molecular hydrogen in the damped Lyman α system towards GRB 120815A at z = 2.36 %+ Dark Cosmology Centre (DARK) %+ AstroParticule et Cosmologie (APC (UMR_7164)) %A Krühler, T. %A Ledoux, C. %A Fynbo, J. P. U. %A Vreeswijk, P. M. %A Schmidl, S. %A Malesani, D. %A Christensen, L. %A de Cia, A. %A Hjorth, J. %A Jakobsson, P. %A Kann, D. A. %A Kaper, L. %A Vergani, S. D. %A Afonso, P. M. J. %A Covino, S. %A de Ugarte Postigo, A. %A D’elia, V. %A Filgas, R. %A Goldoni, P. %A Greiner, J. %A Hartoog, O. E. %A Milvang-Jensen, B. %A Nardini, M. %A Piranomonte, S. %A Rossi, A. %A Sánchez-Ramírez, R. %A Schady, P. %A Schulze, S. %A Sudilovsky, V. %A Tanvir, N. R. %A Tagliaferri, G. %A Watson, D. J. %A Wiersema, K. %A Wijers, R. A. M. J. %A Xu, D. %< avec comité de lecture %@ 0004-6361 %J Astronomy and Astrophysics - A&A %I EDP Sciences %V 557 %P A18 %8 2013 %D 2013 %R 10.1051/0004-6361/201321772 %K ISM: molecules %K galaxies: high-redshift %K gamma-ray burst: individual: GRB 120815A %K galaxies: ISM %K dust %K extinction %Z Physics [physics]/Astrophysics [astro-ph]Journal articles %X We present the discovery of molecular hydrogen (H2), including the presence of vibrationally-excited H2* in the optical spectrum of the afterglow of GRB 120815A at z = 2.36 obtained with X-shooter at the VLT. Simultaneous photometric broad-band data from GROND and X-ray observations by Swift/XRT place further constraints on the amount and nature of dust along the sightline. The galactic environment of GRB 120815A is characterized by a strong DLA with log(N(H i)/cm-2) = 21.95 ± 0.10, prominent H2 absorption in the Lyman-Werner bands (log (N(H2)/cm-2) = 20.54 ± 0.13) and thus a molecular gas fraction log f(H2) = -1.14 ± 0.15. The distance d between the absorbing neutral gas and GRB 120815A is constrained via photo-excitation modeling of fine-structure and meta-stable transitions of Fe ii and Ni ii to d = 0.5 ± 0.1 kpc. The DLA metallicity ([Zn/H] = -1.15 ± 0.12), visual extinction (AV ≲ 0.15 mag) and dust depletion ([Zn/Fe] = 1.01 ± 0.10) are intermediate between the values of well-studied, H2-deficient GRB-DLAs observed at high spectral resolution, and the approximately solar metallicity, highly-obscured and H2-rich GRB 080607 sightline. With respect to N(H i), metallicity, as well as dust-extinction and depletion, GRB 120815A is fairly representative of the average properties of GRB-DLAs. This demonstrates that molecular hydrogen is present in at least a fraction of the more typical GRB-DLAs, and H2 and H2* are probably more wide-spread among GRB-selected systems than the few examples of previous detections would suggest. Because H2* transitions are located redwards of the Lyman α absorption, H2* opens a second route for positive searches for molecular absorption also in GRB afterglows at lower redshifts and observed at lower spectral resolution. Further detections of molecular gas in GRB-DLAs would allow statistical studies, and, coupled with host follow-up and sub-mm spectroscopy, provide unprecedented insights into the process and conditions of star-formation at high redshift. %G English %2 https://cea.hal.science/cea-01135428/document %2 https://cea.hal.science/cea-01135428/file/aa21772-13.pdf %L cea-01135428 %U https://cea.hal.science/cea-01135428 %~ IN2P3 %~ OBSPM %~ CEA %~ UNIV-PARIS7 %~ APC %~ CNRS %~ DSM-IRFU %~ IRFU-APC %~ PSL %~ CEA-DRF %~ UNIV-PARIS %~ UP-SCIENCES %~ OBSPM-PSL