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

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

L. Olmi ¹ and M. Felli <sup>2

1</sup> 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

Abstract

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 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

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Contents

• 1. Introduction
• 2. Observations
• 3. Results
  • 3.1. Morphology
    • 3.1.1. FCRAO observations
    • 3.1.2. IRAM 30-m observations
  • 3.2. Kinematics
  • 3.3. LVG model
• 4. Discussion and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998
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