Monthly Notices of the Royal Astronomical Society | 2019
H I 21 cm mapping of the host galaxy of AT2018cow: a fast-evolving luminous transient within a ring of high column density gas
Abstract
We report Giant Metrewave Radio Telescope H\u2009i 21\u2009cm imaging of CGCG\xa0137–068, the host galaxy of the fast-evolving luminous transient (FELT) AT2018cow. This is the first study of the gas properties of a FELT host galaxy. We obtain a total H\u2009i mass of (6.6\xa0±\xa00.9)\xa0× 10^8\u2009M_⊙ for the host galaxy, which implies an atomic gas depletion time of 3\u2009Gyr and a gas-to-stellar mass ratio of 0.47, consistent with values in normal star-forming dwarf galaxies. At spatial resolutions of ≥6\u2009kpc, the H\u2009i of CGCG\xa0137–068 appears to be distributed in a disc, in mostly regular rotation. However, at spatial resolutions of 2\u2009kpc, the highest column density H\u2009i is found to lie in an asymmetric ring around the central regions, with H\u2009i column densities ≥10^21\u2009cm^−2; AT2018cow lies within this high column density ring. This H\u2009i ring could be suggestive of an interaction between CGCG\xa0137–068 and a companion galaxy. Such a ring is ideal for the formation of compact regions of star formation hosting massive stars, favouring massive star progenitor models for AT2018cow. We measure a 1.4\u2009GHz flux density of 1.13\xa0±\xa00.13\u2009mJy for AT2018cow on 2018 August 27.