GRB 190114C in the nuclear region of an interacting galaxy

A detailed host analysis using ALMA, the HST, and the VLT^⋆

¹ Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía s/n, 18008 Granada, Spain
e-mail: adeugartepostigo@gmail.com
² DARK, Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, 2100 Copenhagen Ø, Denmark
³ European Southern Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
⁴ Joint ALMA Observatory, Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile
⁵ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁶ Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands
⁷ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
⁸ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
⁹ The Cosmic Dawn Center (DAWN), Denmark
¹⁰ Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, 2100 Copenhagen Ø, Denmark
¹¹ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001, Israel
¹² GEPI, Observatoire de Paris, PSL University, CNRS, 5 place Jules Janssen, 92190 Meudon, France
¹³ Institut d’Astrophysique de Paris, Sorbonne Université, CNRS, UMR7095, 75014 Paris, France
¹⁴ Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹⁵ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, LC, Italy
¹⁶ ASI – Space Science Data Centre, Via del Politecnico snc, 00133 Rome, Italy
¹⁷ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, RM, Italy
¹⁸ Department of Astronomy and Space Sciences, Istanbul University, 34119 Beyazıt Istanbul, Turkey
¹⁹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²⁰ Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA
²¹ Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland
²² Department of Physics, The George Washington University, 725 21st Street NW, Washington, DC 20052, USA
²³ Astronomy, Physics, and Statistics Institute of Sciences (APSIS), The George Washington University, Washington, DC 20052, USA
²⁴ GRAPPA Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
²⁵ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
²⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, 40129 Bologna, Italy
²⁷ Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
²⁸ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, Via A. Corti 12, 20133 Milano, Italy
²⁹ INAF, Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133 Roma, Italy
³⁰ CAS Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China

Received: 10 September 2019
Accepted: 18 November 2019

Abstract

Context. For the first time, very high energy emission up to the TeV range has been reported for a gamma-ray burst (GRB). It is still unclear whether the environmental properties of GRB 190114C might have contributed to the production of these very high energy photons, or if it is solely related to the released GRB emission.

Aims. The relatively low redshift of the GRB (z = 0.425) allows us to study the host galaxy of this event in detail, and to potentially identify idiosyncrasies that could point to progenitor characteristics or environmental properties that might be responsible for this unique event.

Methods. We used ultraviolet, optical, infrared, and submillimetre imaging and spectroscopy obtained with the HST, the VLT, and ALMA to obtain an extensive dataset on which the analysis of the host galaxy is based.

Results. The host system is composed of a close pair of interacting galaxies (Δv = 50 km s⁻¹), both of which are well detected by ALMA in CO(3-2). The GRB occurred within the nuclear region (∼170 pc from the centre) of the less massive but more star-forming galaxy of the pair. The host is more massive (log(M/M_⊙) = 9.3) than average GRB hosts at this redshift, and the location of the GRB is rather unique. The higher star formation rate was probably triggered by tidal interactions between the two galaxies. Our ALMA observations indicate that both host galaxy and companion have a high molecular gas fraction, as has been observed before in interacting galaxy pairs.

Conclusions. The location of the GRB within the core of an interacting galaxy with an extinguished line of sight is indicative of a denser environment than typically observed for GRBs and could have been crucial for the generation of the very high energy photons that were observed.