Large-scale mapping of the massive star-forming region RCW38 in the [CII] and PAH emission

TL;DR

This study maps the large-scale structure of the interstellar medium around RCW38 using [CII] and PAH emissions, revealing complex spatial distributions and the role of PAHs in gas heating.

Contribution

It provides the first large-scale [CII] mapping of RCW38 and compares it with PAH and dust emissions, highlighting the spatial correlation and implications for ISM heating processes.

Findings

[CII] emission is highly nonuniform around RCW38.

[CII] correlates better with PAH emission than dust emission.

Molecular clouds are located both on and behind the cluster.

Abstract

We investigate the large-scale structure of the interstellar medium (ISM) around the massive star cluster RCW38 in the [CII] 158 um line and polycyclic aromatic hydrocarbon (PAH) emission. We carried out [CII] line mapping of an area of ~30'x15' for RCW~38 by a Fabry-Perot spectrometer on a 100 cm balloon-borne telescope with an angular resolution of ~1'.5. We compared the [CII] intensity map with the PAH and dust emission maps obtained by the AKARI satellite. The [CII] emission shows a highly nonuniform distribution around the cluster, exhibiting the structure widely extended to the north and the east from the center. The [CII] intensity rapidly drops toward the southwest direction, where a CO cloud appears to dominate. We decompose the 3-160 um spectral energy distributions of the surrounding ISM structure into PAH as well as warm and cool dust components with the help of 2.5-5 um spectra. We find that the [CII] emission spatially corresponds to the PAH emission better than to the dust emission, confirming the relative importance of PAHs for photo-electric heating of gas in photo-dissociation regions. A naive interpretation based on our observational results indicates that molecular clouds associated with RCW38 are located both on the side of and behind the cluster.