The PDR structure and kinematics around the compact H ii regions S235 A and S235 C with [C ii], [13C ii], [O i], and HCO+ line profiles
| Autor: | Volker Ossenkopf-Okada, Christof Buchbender, Nicola Schneider, Rebeca Aladro, Matteo Luisi, Maria S. Kirsanova, A. M. Sobolev, M. R. Samal, Paul A. Boley, L. D. Anderson, John H. Bieging, Yoko Okada, Morten Andersen, Ya. N. Pavlyuchenkov |
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| Rok vydání: | 2020 |
| Předmět: |
ISM [INFRARED]
Physics H II REGIONS KINEMATICS AND DYNAMICS [ISM] 010308 nuclear & particles physics Molecular cloud Photodissociation FOS: Physical sciences Astronomy and Astrophysics RADIATIVE TRANSFER Kinematics Astrophysics Astrophysics - Astrophysics of Galaxies 01 natural sciences Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences Radiative transfer PROFILES [LINE] PHOTODISSOCIATION REGION (PDR) 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Optical depth Line (formation) |
| Zdroj: | Mon. Not. R. Astron. Soc. Monthly Notices of the Royal Astronomical Society |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/staa2142 |
| Popis: | The aim of the present work is to study structure and gas kinematics in the photodissociation regions (PDRs) around the compact HII regions S235A and S235C. We observe the [CII], [13CII] and [OI] line emission, using SOFIA/upGREAT and complement them by data of HCO+ and CO. We use the [13CII] line to measure the optical depth of the [CII] emission, and find that the [CII] line profiles are influenced by self-absorption, while the [13CII] line remains unaffected by these effects. Hence, for dense PDRs, [13CII] emission is a better tracer of gas kinematics. The optical depth of the [CII] line is up to 10 in S235A. We find an expanding motion of the [CII]-emitting layer of the PDRs into the front molecular layer in both regions. Comparison of the gas and dust columns shows that gas components visible neither in the [CII] nor in low-J CO lines may contribute to the total column across S235A. We test whether the observed properties of the PDRs match the predictions of spherical models of expanding HII region + PDR + molecular cloud. Integrated intensities of the [13CII], [CII] and [OI] lines are well-represented by the model, but the models do not reproduce the double-peaked [CII] line profiles due to an insufficient column density of C+. The model predicts that the [OI] line could be a more reliable tracer of gas kinematics, but the foreground self-absorbing material does not allow using it in the considered regions. Comment: accepted to MNRAS |
| Databáze: | OpenAIRE |
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