Arabsalmani, M.M.ArabsalmaniRoychowdhury, S.S.RoychowdhuryStarkenburg, T. K.T. K.StarkenburgChristensen, L.L.ChristensenLe Floc'h, E.E.Le Floc'hKanekar, N.N.KanekarBournaud, F.F.BournaudZwaan, M. A.M. A.ZwaanFynbo, J. P. U.J. P. U.FynboMøller, P.P.MøllerPIAN, ElenaElenaPIAN2020-12-072020-12-0720190035-8711http://hdl.handle.net/20.500.12386/28731We 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 0.004 M_{☉ } yr^{-1}, a gas mass of 10^{7.1± 0.1} M_{☉}, and a stellar mass of 10^{7.0± 0.3} M_{☉}. 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.STAMPAenArticle10.1093/mnras/stz7352-s2.0-85067015276000474880400070https://academic.oup.com/mnras/article/485/4/5411/53808122019MNRAS.485.5411AFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems