The host galaxy of FRB 20171020A revisited

The putative host galaxy of FRB 20171020A was first identified as ESO 601-G036 in 2018, but as no repeat bursts have been detected, direct confirmation of the host remains elusive. In light of recent developments in the field, we re-examine this host and determine a new association confidence level of 98%. At 37 Mpc, this makes ESO 601-G036 the third closest FRB host galaxy to be identified to date and the closest to host an apparently non-repeating FRB (with an estimated repetition rate limit of <0.011 bursts per day above 10(39) erg). Due to its close distance, we are able to perform detailed multi-wavelength analysis on the ESO 601-G036 system. Follow-up observations confirm ESO 601-G036 to be a typical star-forming galaxy with H I and stellar masses of log10(M-HI/M-circle dot) similar to 9.2 and log(10)(M-star/M-circle dot) = 8.64(-0.15)(+0.03) , and a star formation rate of SFR= 0.09 +/- 0.01M(circle dot) yr(-1). We detect, for the first time, a diffuse gaseous tail (log(10)(MH I/M-circle dot) similar to 8.3) extending to the south-west that suggests recent interactions, likely with the confirmed nearby companion ESO 601-G037. ESO 601-G037 is a stellar shred located to the south of ESO 601-G036 that has an arc-like morphology, is about an order of magnitude less massive, and has a lower gas metallicity that is indicative of a younger stellar population. The properties of the ESO 601-G036 system indicate an ongoing minor merger event, which is affecting the overall gaseous component of the system and the stars within ESO 601-G037. Such activity is consistent with current FRB progenitor models involving magnetars and the signs of recent interactions in other nearby FRB host galaxies.

Automated summary

The potential host galaxy of FRB 20171020A was identified as ESO 601-G036 in 2018, but confirmation is still lacking. Recent developments have led to a re-examination, resulting in a new association confidence level of 98%. The ESO 601-G036 system shows signs of ongoing minor merger events, and detailed multi-wavelength analysis reveals it to be a typical star-forming galaxy.