Triggered massive-star formation on the borders of Galactic H II regions. III. Star formation at the periphery of Sh2-219 - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2006

Triggered massive-star formation on the borders of Galactic H II regions. III. Star formation at the periphery of Sh2-219

L. Deharveng
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B. Lefloch
F. Massi
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J. Brand
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S. Kurtz
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Annie Zavagno
J. Caplan
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Résumé

Context: .Massive-star formation triggered by the expansion of H ii regions. Aims: .To understand if sequential star formation is taking place at the periphery of the H ii region Sh2-219. Methods: .We present 12CO J=2→ 1 line observations of this region, obtained at the IRAM 30-m telescope (Pico Veleta, Spain). Results: .In the optical, Sh2-219 is spherically symmetric around its exciting star; furthermore it is surrounded along three quarters of its periphery by a ring of atomic hydrogen. This spherical symmetry breaks down at infrared and millimetre wavelengths. A molecular cloud of about 2000 M_ȯ lies at the southwestern border of Sh2-219, in the H i gap. Two molecular condensations, elongated along the ionization front, probably result from the interaction between the expanding H ii region and the molecular cloud. In this region of interaction there lies a cluster containing many highly reddened stars, as well as a massive star exciting an ultracompact H ii region. More surprisingly, the brightest parts of the molecular cloud form a "chimney", perpendicular to the ionization front. This chimney is closed at its south-west extremity by Hα walls, thus forming a cavity. The whole structure is 7.5 pc long. A luminous Hα emission-line star, lying at one end of the chimney near the ionization front, may be responsible for this structure. Confrontation of the observations with models of H ii region evolution shows that Sh2-219 is probably 105 yr old. The age and origin of the near-IR cluster observed on the border of Sh2-219 remain unknown.

Dates et versions

hal-00398261 , version 1 (24-06-2009)

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L. Deharveng, B. Lefloch, F. Massi, J. Brand, S. Kurtz, et al.. Triggered massive-star formation on the borders of Galactic H II regions. III. Star formation at the periphery of Sh2-219. Astronomy and Astrophysics - A&A, 2006, 458, pp.191. ⟨10.1051/0004-6361:20054641⟩. ⟨hal-00398261⟩
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