2024MNRAS.531.4045C

NGC 613 is a nearby barred spiral galaxy with a nuclear ring. Exploiting high spatial resolution (≈20 pc) Atacama Large Millimetre/submillimetre Array ¹²CO(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 (R_c) are comparable to those of the clouds in the Milky Way (MW) disc, but their gas masses, observed linewidths (σ_obs,los), and gas mass surface densities are larger. The GMC size-linewidth relation ($\sigma _{\mathrm{obs,los}}\propto R_{\mathrm{c}}^{0.77}$) 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 〈α_obs,vir〉 ≈ 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.