2021MNRAS.504.4511P

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of ¹³CO(J = 1-0) line and 104 GHz continuum emission from NGC 604, a giant H II region (GHR) in the nearby spiral galaxy M33. Our high spatial resolution images (3.2 arcsec x 2.4 arcsec, corresponding to 13 x 10 pc physical scale) allow us to detect 15 molecular clouds. We find spatial offsets between the ¹³CO and 104 GHz continuum emission and also detect continuum emission near the centre of the GHR. The identified molecular clouds have sizes ranging from 5-21 pc, linewidths of 0.3-3.0 km s^–1 and luminosity-derived masses of (0.4-80.5) x 10³ M_☉. These molecular clouds are in near virial equilibrium, with a spearman correlation coefficient of 0.98. The linewidth-size relationship for these clouds is offset from the corresponding relations for the Milky Way and for NGC 300, although this may be an artefact of the dendrogram process.