Letter to the Editor

Triggered massive-star formation at the border of the HII region Sh 104

¹ Laboratoire d'Astrophysique de Marseille, 2 place le Verrier, 13248 Marseille Cedex 4, France
² Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 rue de la Piscine, BP 53, 38041 Grenoble Cedex 9, France
³ Department of Physics and Astronomy, University of Wales, Cardiff CF24 3YB, Wales, UK
⁴ Observatoire du Mont Megantic et Département de Physique, Université de Montréal, CP 6128, Succ. Centre-Ville, Montréal, QC, Canada, H3C3J7
⁵ IRAM, Avenida Divina Pastora, 7, 18012 Granada, Spain

Corresponding author: L. Deharveng, lise.deharveng@oamp.fr

Received: 19 June 2003
Accepted: 29 July 2003

Abstract

We present millimetre-line imaging of the Galactic H ii region Sh 104. We show that it is surrounded by a ring of molecular gas and dust. Four large molecular condensations are regularly spaced around the ring. These condensations are themselves fragmented and contain several massive dense cores. A deeply embedded cluster is observed in the near IR towards the largest condensation. It contains at least one massive star ionizing an ultra-compact H ii region. The Sh 104 region is a good illustration of the “collect and collapse” model for star formation triggered by the expansion of an H ii region.