[CII] emission properties of the massive star-forming region RCW36 in a filamentary molecular cloud

Abstract

Aims: To investigate properties of [CII]158 $\mu$m emission of RCW36 in a dense filamentary cloud. Methods: [CII] observations of RCW36 covering an area of ~30 arcmin$\times$30 arcmin were carried out with a Fabry-Pérot spectrometer aboard a 100-cm balloon-borne far-infrared (IR) telescope with an angular resolution of 90 arcsec. By using AKARI and Herschel images, the spatial distribution of the [CII] intensity was compared with those of emission from the large grains and PAH. Results: The [CII] emission is spatially in good agreement with shell-like structures of a bipolar lobe observed in IR images, which extend along the direction perpendicular to the direction of a cold dense filament. We found that the [CII]--160 $\mu$m relation for RCW36 shows higher brightness ratio of [CII]/160 $\mu$m than that for RCW 38, while the [CII]--9 $\mu$m relation for RCW36 is in good agreement with that for RCW38. Conclusions: The [CII] emission spatially well correlates with PAH and cold dust emissions. This means that the observed [CII] emission dominantly comes from PDRs. Moreover, the L_[CII]/L_FIR ratio shows large variation compared with the L_[CII]/L_PAH ratio. In view of the observed tight correlation between L_[CII]/L_FIR and the optical depth at $\lambda$=160 $\mu$m, the large variation in L_[CII]/L_FIR can be simply explained by the geometrical effect, viz., L_FIR has contributions from the entire dust-cloud column along the line of sight, while L_[CII] has contributions from far-UV illuminated cloud surfaces. Based on the picture of the geometry effect, the enhanced brightness ratio of [CII]/160 $\mu$m is attributed to the difference in gas structures where massive stars are formed: filamentary (RCW36) and clumpy (RCW38) molecular clouds and thus suggests that RCW36 is dominated by far-UV illuminated cloud surfaces compared with RCW38.

9 pages, 11 figures, accepted for publication in A&A

References in corpus (6)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Filamentary structure of star-forming complexes
• The Spatially Resolved [CII] Cooling Line Deficit in Galaxies
• X-ray and IR Point Source Identification and Characteristics In the Embedded, Massive Star-Forming Region RCW 38
• New insights in the mid-infrared bubble N49 site: a clue of collision of filamentary molecular clouds
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Cited by in corpus (3)

• The SOFIA FEEDBACK Legacy Survey: Dynamics and mass ejection in the bipolar HII region RCW 36
• The origin and evolution of the [CII] deficit in HII regions and star-forming molecular clouds
• TIFR Treasures for Astronomy from Ground to Space