Star formation in the bright rimmed globule IC 1396N

¹ Istituto di Fisica dello Spazio Interplanetario, CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma, Italy
² Observatorio Astronómico Nacional (IGN), Apartado 1143, 28800 Alcalá de Henares (Madrid), Spain
³ Osservatorio Astronomico di Roma, Via di Frascati 33, 00040 Monteporzio, Italy
⁴ Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Corresponding author: C. Codella, codella@ifsi.rm.cnr.it

Received: 13 February 2001
Accepted: 2 July 2001

Abstract

We report mm-wave multiline and continuum observations of IC 1396N, a conspicuous bright, rimmed globule excited by the O6.5 star HD 206267 in the Cep OB2 association. Single-dish high resolution observations in CO and CS lines reveal the cometary structure of the globule with unprecedented detail. The globule head contains a dense core of 0.2 pc, whereas the tail, pointing away from the exciting star, has a total length of 0.8 pc. Two high velocity bipolar outflows have been identified in the CO maps: the first one is located around the position of a strong IRAS source in the head of the globule, and the second one, which was previously unknown, is located in the northern region. The outflows emerge from high density clumps which exhibit strong line emission of CS, HCO⁺, and DCO⁺. Within these clumps, the sources driving the outflows have been identified thanks to mm-wave continuum observations. The globule head harbors two YSOs separated by about 10⁴ AU. SiO line observations of the central outflow unveals a highly collimated structure with four clumps of sizes pc, which are located along the outflow axis and suggest episodic events in the mass loss process from the central star. Kinetic temperatures of K and hydrogen densities of fews 10⁶ cm^-3 have been estimated in the shocked regions traced by the strong SiO emission. The jet is also exposed to view by the means of interferometric HCO⁺ observations that confirms that it is very narrow ( pc wide). The detection of blue- and redshifted CO emission along the globule rim suggests that IC 1396N is in a transient phase, undergoing one of the expansions or compressions predicted by theoretical models describing the evolution of cometary globules. Moreover, the CO data, together with near IR observations reported elsewhere, indicate that the star forming process is occurring also in the northern part of IC 1396N, at 0.5 pc from the central CS peak. The present observations provide evidence that several star-forming sites can develop even in a moderately massive globule like IC 1396N.