  The nature of the newly discovered fast blue optical transients (FBOTs) is
still puzzling astronomers. In this paper we carry out a comprehensive analysis
of the molecular gas, ionized gas and stellar populations in the environment of
the nearby FBOT AT2018cow based on ALMA, VLT/MUSE and HST/WFC3 observations. A
prominent molecular concentration of 6 ($\pm$ 1) $\times$ 10$^6$ $M_\odot$ is
found in the vicinity of AT2018cow, which has given rise to two active
star-forming complexes with ages of 4 $\pm$ 1 Myr and $\lesssim$2.5 Myr,
respectively. Each star-forming complex has a stellar mass of 3 $\times$ 10$^5$
$M_\odot$ and has photoionized a giant H II region with H$\alpha$ luminosity
even comparable to that of the 30 Dor mini-starburst region. AT2018cow is
spatially coincident with one of the star-forming complexes; however, it is
most likely to reside in its foreground since it has a much smaller extinction
than the complex. Its progenitor could have been formed in a different
star-forming event, and the non-detection of the associated stellar population
constrains the progenitor's age to be $\gtrsim$10 Myr and initial mass to be
$\lesssim$ 20 $M_\odot$. We further find the late-time brightness of AT2018cow
is unlikely to be a stellar object. Its brightness has slightly declined from 2
yr to 4 yr after explosion and is most likely to originate from AT2018cow
itself due to some powering mechanism still working at such late times.

Astrophysics of Galaxies;Solar and Stellar Astrophysics