| Issue |
A&A
Volume 482, Number 2, May I 2008
|
|
|---|---|---|
| Page(s) | 585 - 596 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361:20079233 | |
| Published online | 20 February 2008 | |
Triggered massive-star formation on the borders of Galactic H II regions *,**
IV. Star formation at the periphery of Sh2-212
1
Laboratoire d'Astrophysique de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 4, France e-mail: lise.deharveng@oamp.fr
2
Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9, France
3
Centro de Radioastronomía y Astrofísica, UNAM, Apartado Postal 3-72, 58089, Morelia, Michoacán, México
4
Observatoire du Mont Mégantic et Département de Physique, Université de Montréal, CP 6128, Succ. Centre-Ville, Montréal, H3C3J7, QC, Canada
Received:
11
December
2007
Accepted:
8
February
2008
Aims. We wish to establish whether sequential star formation is taking place at the periphery of the Galactic H ii region Sh2-212.
Methods. We present CO millimetre observations of this region obtained at the IRAM
30-m telescope to investigate the distribution of associated molecular material.
We also use deep 
observations obtained at the CFHT to
study the stellar content of the region, and radio observations obtained
at the VLA to look for the presence of an ultra-compact (UC) H ii region
and for maser emission.
Results. In the optical, Sh2-212 is spherically symmetric around its central exciting
cluster. This H ii region is located along a molecular filament. A thin,
well-defined half ring of molecular material surrounds the brightest part of
the H ii region at the rear and is fragmented. The most massive
fragment (~200 
) contains a massive young stellar object displaying
a near-IR excess; its spectral energy distribution indicates a high-mass
(~14 ), high-temperature (~30 000 K), and high-luminosity
(~17 000 
) source. This object ionizes a UC H ii region.
Conclusions. Sh2-212 is a good example of massive-star formation triggered via the collect and collapse process. The massive YSO observed at its periphery is a good candidate for a massive star formed in isolation.
Key words: stars: formation / stars: early-type / ISM: H ii regions / ISM: individual objects: Sh2-212
© ESO, 2008
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