Volume 458, Number 1, October IV 2006
|Page(s)||191 - 201|
|Section||Interstellar and circumstellar matter|
|Published online||16 October 2006|
Triggered massive-star formation on the borders of Galactic H II regions
III. Star formation at the periphery of Sh2-219
Laboratoire d'Astrophysique de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 4, France e-mail: email@example.com
2 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9, France
3 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4 INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
5 Centro de Radioastronomía y Astrofísica, UNAM, Apartado Postal 3-72, 58089 Morelia, Michoacán, México
Accepted: 10 July 2006
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 CO 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 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.
Key words: stars: formation / stars: early-type / ISM: H ii regions / ISM: individual objects: Sh2-219
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.