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Astron. Astrophys. 339, 872-879 (1998)

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CS observations of the hotspot at the S 155/Cepheus B interface

L. Olmi 1 and M. Felli 2

1 LMT Project and FCRAO, University of Massachusetts, 630 L.G.R.C., Amherst, MA 01003, USA (olmi@fcrao1.phast.umass.edu)
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy (felli@arcetri.astro.it)

Received 17 February 1998 / Accepted 10 August 1998


We have used the IRAM 30-m telescope to map, in the J=2-1, J=3-2 and J=5-4 rotational transitions of CS, the molecular hotspot located south-east of the Cepheus OB3 association, at the interface that divides the S 155 diffuse HII region from the Cepheus B molecular cloud. We have also used the FCRAO 13.7-m telescope to map the larger scale CS(2-1) emission. The [FORMULA] segment that has been mapped at higher spatial resolution with the 30-m telescope covers four radio continuum sources, one of which (source A) is a blister-type HII region. By using the CS molecule we analyse: i) the molecular density at the interface region and ii) the kinematics of the molecular gas at the front. The observations confirm that the blister has created a cavity at the edge of the molecular hotspot and is bounded on its sharp side by a dense mlecular front in pressure equilibrium with the ionized gas. The near-IR star at the centre of the blister (A-NIR) is responsible for its ionization and for the heating of the hotspot .

Key words: HII regions – ISM: molecules – stars: formation – radio lines: ISM

Send offprint requests to: L. Olmi

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998