2009/01/30 by L. Deharveng, A. Zavagno, F. Schüller +4 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Context (archaeology) #Galaxies: Formation, Evolution, Phenomena #Geology #H II region #Physics #Star formation #Stars #Stellar, planetary, and galactic studies #Young stellar object #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/200811337
14 pages, 17 figures
openalex publication_date 2009/01/30 · arxiv created 2009/02/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
<i>Context. <i/> This study deals with the star formation triggered by H ii regions.<i>Aims. <i/>We wish to take advantage of the very simple morphology of RCW 120 – a perfect bubble – to understand the mechanisms triggering star formation around an H ii region and to establish what kind of stars are formed there.<i>Methods. <i/>We present 870 <i>μ<i/>m observations of RCW 120, obtained with the APEX-LABOCA camera. These show the distribution of cold dust, and thus of neutral material. We use Spitzer-MIPS observations at 24 <i>μ<i/>m and 70 <i>μ<i/>m to detect the young stellar objects present in this region and to estimate their evolutionary stages.<i>Results. <i/>A layer of dense neutral material surrounds the entire H ii region, having been swept up during the region's expansion. This layer has a mass greater than and is fragmented, with massive fragments elongated along the ionization front (IF). We measured the 24 <i>μ<i/>m flux of 138 sources. Of these, 39 are Class I or flat-spectrum young stellar objects (YSOs) observed in the direction of the collected layer. We show that several triggering mechanisms are acting simultaneously in the swept-up shell, where they form a second generation of stars. No massive YSOs are detected. However, a massive, compact 870 <i>μ<i/>m core lies adjacent to the IF. A 70 <i>μ<i/>m source with no 24 <i>μ<i/>m counterpart is detected at the same position. This source is a likely candidate for a Class 0 YSO. Also at 24 <i>μ<i/>m, we detect a chain of about ten regularly spaced Class I or flat spectrum sources, parallel to the IF, in the direction of the most massive fragment. We suggest that the formation of these YSOs is the result of Jeans gravitational instabilities in the collected layer. Finally, the 870 <i>μ<i/>m emission, the 24 <i>μ<i/>m emission, and the H<i>α<i/> emission show the existence of an extended and partially ionized photodissociation region around RCW 120. This demonstrates the long-distance influence of the H ii region upon its surrounding medium.