WISDOM Project - XXI. Giant molecular clouds in the central region of the barred spiral galaxy NGC 613: a steep size-linewidth relation

NGC 613 is a nearby barred spiral galaxy with a nuclear ring. Exploiting high spatial resolution ( approximate to 20 pc) Atacama Large Millimetre/submillimetre Array (12) CO(1-0) observations, we study the giant molecular clouds (GMCs) in the nuclear ring and its vicinity, identifying 158 spatially and spectrally resolved GMCs. The GMC sizes (Rc) R- c ) are comparable to those of the clouds in the Milky Way (MW) disc, but their gas masses, observed linewidths ( sigma (obs,los)), ), and gas mass surface densities are larger. The GMC size-linewidth relation ( sigma (obs , los) oc R- c (0 . 77) ) is steeper than that of the clouds of the MW disc and centre, and the GMCs are on average only marginally gravitationally bound (with a mean virial parameter ( alpha (obs,vir) ) approximate to 1.7). We discuss the possible origins of the steep size-linewidth relation and enhanced observed linewidths of the clouds and suggest that a combination of mechanisms such as stellar feedback, gas accretion, and cloud-cloud collisions, as well as the gas inflows driven by the large-scale bar, may play a role.