M33 center and BCLMP302 [CII] spectroscopy

We aim to understand the contribution of the ionized, atomic and molecular phases of the ISM to the [CII] emission from clouds near the dynamical center and the BCLMP302 HII region in the north of the nearby galaxy M33 at a spatial resolution of 50pc. We combine high resolution [CII] spectra taken with the Herschel/HIFI spectrometer onboard the Herschel satellite with [CII] Herschel-PACS maps and ground-based observations of CO(2-1) with IRAM 30m and HI with VLA, all at the same spatial resolution.

We decomposed the [CII] spectra in terms of contribution from molecular and atomic gas detected in CO(2-1) and HI, respectively. Typically, the [CII] lines have widths intermediate between the narrower CO(2-1) and broader HI line profiles. Comparison of spectra show that the relative contribution of molecular and atomic gas traced by CO(2-1) and HI varies substantially between positions and depends mostly on the local physical conditions and geometry.