Details

Autor(en) / Beteiligte

• Kirsanova, M. S
• Wiebe, D. S
• Sobolev, A. M
• Henkel, C
• Tsivilev, A. P

Titel

Physical conditions in star-forming regions around S235

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2014-01, Vol.437 (2), p.1593-1608

Ort / Verlag

London: Oxford University Press

Erscheinungsjahr

2014

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Gas density and temperature in star-forming regions around Sh2-235 are derived from ammonia line observations. This information is used to evaluate formation scenarios and to determine evolutionary stages of the young embedded clusters S235 East 1, S235 East 2 and S235 Central. We also estimate the gas mass in the embedded clusters and its ratio to the stellar mass. S235 East 1 appears to be less evolved than S235 East 2 and S235 Central. In S235 East 1 the molecular gas mass exceeds that in the other clusters. Also, this cluster is more embedded in the parent gas cloud than the other two. Comparison with a theoretical model shows that the formation of these three clusters could have been stimulated by the expansion of the Sh2-235 H ii region (hereafter S235) via a collect-and-collapse process, provided the density in the surrounding gas exceeds 3 × 103 cm−3, or via collapse of pre-existing clumps. The expansion of S235 cannot be responsible for star formation in the southern S235 A-B region. However, formation of the massive stars in this region might have been triggered by a large-scale supernova shock. Thus, triggered star formation in the studied region may come in three varieties, namely collect-and-collapse and collapse of pre-existing clumps, both initiated by expansion of the local H ii regions, and triggered by an external large-scale shock. We argue that the S235 A H ii region expands into a highly non-uniform medium with increasing density. It is too young to trigger star formation in its vicinity by a collect-and-collapse process. There is an age spread inside the S235 A-B region. Massive stars in the S235 A-B region are considerably younger than lower mass stars in the same area. This follows from the estimates of their ages and the ages of associated H ii regions.