The warm, the excited, and the molecular gas: GRB 121024A shining through its star-forming galaxy

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Friis, M., De Cia, A., Kruehler, T., Fynbo, J. P. U., Ledoux, C., Vreeswijk, P. M., Watson, D. J., Malesani, D., Gorosabel, J., Starling, R. L. C., Jakobsson, P., Varela, K., Wiersema, K., Drachmann, A. P., Trotter, A., Thoene, C. C., de Ugarte Postigo, A., D'Elia, V., Elliott, J., Maturi, M., Goldoni, P., Greiner, J., Haislip, J., Kaper, L., Knust, F., LaCluyze, A., Milvang Jensen, B., Reichart, D., Schulze, S., Sudilovsky, V., Tanvir, N., Vergani, S. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: OXFORD UNIV PRESS 2024
• Subjects: gamma-ray burst: individual: GRB 121024A; galaxies: abundances; GAMMA-RAY BURST; MASS-METALLICITY RELATION; DAMPED LYMAN; AFTERGLOW SPECTROSCOPY; CHEMICAL-COMPOSITION; INTERSTELLAR-MEDIUM; EXTINCTION CURVES; SOLAR-METALLICITY; DUST EXTINCTION; ABSORPTION-LINE; 07 Affordable and Clean Energy; 07 Energía asequible y no contaminante; Lya; Iceland
• Online Access: https://repositorio.uc.cl/handle/11534/76548; https://doi.org/10.1093/mnras/stv960

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. 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 Ramon y Cajal fellowship Spanish research project European Commission CONICYT-Chile ...