The host galaxy of GRB 980425 / SN1998bw: a collisional ring galaxy

M. Arabsalmani*, S. Roychowdhury, T. K. Starkenburg, L. Christensen, E. Le Floc’h, N. Kanekar, F. Bournaud, M. A. Zwaan, J. P. U. Fynbo, P. Møller, E. Pian

*Corresponding author for this work

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Abstract

We report Giant Metrewave Radio Telescope (GMRT) , Very Large Telescope (VLT) and Spitzer Space Telescope observations of ESO 184−G82, the host galaxy of GRB 980425/SN 1998bw, that yield evidence of a companion dwarf galaxy at a projected distance of 13 kpc. The companion, hereafter GALJ193510-524947, is a gas-rich, star-forming galaxy with a star formation rate of 0.004M⊙yr−1⁠, a gas mass of 107.1 ± 0.1M⊙, and a stellar mass of 107.0 ± 0.3M⊙. The interaction between ESO 184−G82 and GALJ193510-524947 is evident from the extended gaseous structure between the two galaxies in the GMRT H i 21 cm map. We find a ring of high column density H i gas, passing through the actively star forming regions of ESO 184−G82 and the GRB location. This ring lends support to the picture in which ESO 184−G82 is interacting with GALJ193510-524947. The massive stars in GALJ193510-524947 have similar ages to those in star-forming regions in ESO 184−G82, also suggesting that the interaction may have triggered star formation in both galaxies. The gas and star formation properties of ESO 184−G82 favour a head-on collision with GALJ193510-524947 rather than a classical tidal interaction. We perform state-of-the art simulations of dwarf–dwarf mergers and confirm that the observed properties of ESO 184−G82 can be reproduced by collision with a small companion galaxy. This is a very clear case of interaction in a gamma ray burst host galaxy, and of interaction-driven star formation giving rise to a gamma ray burst in a dense environment.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume485
Issue number4
Pages (from-to)5411–5422
ISSN0035-8711
DOIs
Publication statusPublished - 2019

Bibliographical note

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record is available online at: https://doi.org/10.1093/mnras/stz735

Keywords

  • Gamma-ray burst: general
  • Galaxies: ISM
  • Galaxies: star formation
  • Galaxies: kinematics and dynamics
  • Galaxies: interactions
  • Radio lines: galaxies

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