Globules and pillars in Cygnus X III. Herschel and upGREAT/SOFIA far-infrared spectroscopy of the globule IRAS 20319+3958 in Cygnus X

• Published in: Astronomy and astrophysics (Berlin) Vol. 653; p. A108
• Main Authors: Schneider, N., Röllig, M., Polehampton, E. T., Comerón, F., Djupvik, A. A., Makai, Z., Buchbender, C., Simon, R., Bontemps, S., Güsten, R., White, G., Okada, Y., Parikka, A., Rothbart, N.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.09.2021
• Subjects: Astrophysics; Sciences of the Universe; photon-dominated region; Astrophysics - Astrophysics of Galaxies; ISM: atoms; ISM: molecules; ISM: kinematics and dynamics; ISM: clouds; HII regions
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361/202140824

IRAS 20319+3958 in Cygnus X South is a rare example of a free-floating globule (mass ~240 M ⊙ , length ~1.5 pc) with an internal H  II region created by the stellar feedback of embedded intermediate-mass stars, in particular, one Herbig Be star. In Schneider et al. 2012, (A&A, 542, L18) and Djupvik et al. 2017, (A&A, 599, A37), we proposed that the emission of the far-infrared (FIR) lines of [C  II ] at 158 μm and [O  I ] at 145 μm in the globule head are mostly due to an internal photodissociation region (PDR). Here, we present a Herschel /HIFI [C  II ] 158 μm map of the whole globule and a large set of other FIR lines (mid-to high- J CO lines observed with Herschel /PACS and SPIRE, the [O  I ] 63 μm line and the 12 CO 16→15 line observed with upGREAT on SOFIA), covering the globule head and partly a position in the tail. The [C  II ] map revealed that the whole globule is probably rotating. Highly collimated, high-velocity [C  II ] emission is detected close to the Herbig Be star. We performed a PDR analysis using the KOSMA- τ PDR code for one position in the head and one in the tail. The observed FIR lines in the head can be reproduced with a two-component model: an extended, non-clumpy outer PDR shell and a clumpy, dense, and thin inner PDR layer, representing the interface between the H  II region cavity and the external PDR. The modelled internal UV field of ~2500 G ° is similar to what we obtained from the Herschel FIR fluxes, but lower than what we estimated from the census of the embedded stars. External illumination from the ~30 pc distant Cyg OB2 cluster, producing an UV field of ~150–600 G ° as an upper limit, is responsible for most of the [C  II ] emission. For the tail, we modelled the emission with a non-clumpy component, exposed to a UV-field of around 140 G ° .