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X-shooter and ALMA spectroscopy of GRB 161023A A study of metals and molecules in the line of sight towards a luminous GRB

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posted on 2019-08-15, 16:07 authored by A de Ugarte Postigo, CC Thone, J Bolmer, S Schulze, S Martin, DA Kann, V D'Elia, J Selsing, A Martin-Carrillo, DA Perley, S Kim, L Izzo, R Sanchez-Ramirez, C Guidorzi, A Klotz, K Wiersema, FE Bauer, K Bensch, S Campana, Z Cano, S Covino, D Coward, A De Cia, I de Gregorio-Monsalvo, M De Pasquale, JPU Fynbo, J Greiner, A Gomboc, L Hanlon, M Hansen, DH Hartmann, KE Heintz, P Jakobsson, S Kobayashi, DB Malesani, R Martone, PJ Meintjes, MJ Michalowski, CG Mundell, D Murphy, S Oates, L Salmon, B van Soelen, NR Tanvir, D Turpin, D Xu, T Zafar
Context. Long gamma-ray bursts (GRBs) are produced during the dramatic deaths of massive stars with very short lifetimes, meaning that they explode close to the birth place of their progenitors. Over a short period they become the most luminous objects observable in the Universe, being perfect beacons to study high-redshift star-forming regions. Aims. We aim to use the afterglow of GRB 161023A at a redshift z = 2.710 as a background source to study the environment of the explosion and the intervening systems along its line of sight. Methods. For the first time, we complement ultraviolet (UV), optical and near-infrared (NIR) spectroscopy with millimetre spectroscopy using the Atacama Large Millimeter Array (ALMA), which allows us to probe the molecular content of the host galaxy. The X-shooter spectrum shows a plethora of absorption features including fine-structure and metastable transitions of Fe, Ni, Si, C, and O. We present photometry ranging from 43 s to over 500 days after the burst. Results. We infer a host-galaxy metallicity of [Zn/H] = −1.11±0.07, which, corrected for dust depletion, results in [X/H] = −0.94±0.08. We do not detect molecular features in the ALMA data, but we derive limits on the molecular content of log(NCO/cm−2 ) < 15.7 and log(NHCO+/cm−2 ) < 13.2, which are consistent with those that we obtain from the optical spectra, log(NH2 /cm−2 ) < 15.2 and log(NCO/cm−2 ) < 14.5. Within the host galaxy, we detect three velocity systems through UV, optical and NIR absorption spectroscopy, all with levels that were excited by the GRB afterglow. We determine the distance from these systems to the GRB to be in the range between 0.7 and 1.0 kpc. The sight line to GRB 161023A shows nine independent intervening systems, most of them with multiple components. Conclusions. Although no molecular absorption was detected for GRB 161023A, we show that GRB millimetre spectroscopy is now feasible and is opening a new window on the study of molecular gas within star-forming galaxies at all redshifts. The most favoured lines of sight for this purpose will be those with high metallicity and dust.


AdUP and CT acknowledge support from Ramón y Cajal fellowships RyC-2012-09975 and RyC-2012-09984 and the Spanish Ministry of Economy and Competitiveness through projects AYA2014-58381-P and AYA2017-89384-P, AdUP furthermore from the BBVA foundation. DAK acknowledges support from the Spanish research project AYA 2014-58381-P, and from Juan de la Cierva Incorporación fellowship IJCI-2015-26153. FEB acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007) and the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. 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).JB acknowledges support through the Sofja Kovalevskaja Award to P. Schady from the Alexander von Humboldt Foundation of Germany. MJM acknowledges the support of the National Science Centre, Poland through the POLONEZ grant 2015/19/P/ST9/04010; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 665778. AG acknowledges the financial support from the Slovenian Research Agency (research core funding No. P1-0031 and project grant No. J1-8136) and networking support by the COST Action GWverse CA16104. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 098.A-0055, 098.D-0710 and 0100.D-0649. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.00862.T. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This work is based in part on observatio



Astronomy and Astrophysics, 2018, 620, A119

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