The Photoionization of a Star-Forming Core in the Trifid Nebula

We have carried out a comprehensive multiwavelength study of BrightRimmed Globule TC2 in the Trifid Nebula, using the IRAM 30m telescope, the VLA centimeter array and the Infrared Space Observatory (ISO). TC2 is one of the very few globules to exhibit signs of active ongoing star formation while being photoevaporated by the Ly-c flux of the exciting star of the nebula (∼ 10 cm s). The globule consists of a cold dense core of mass 27M⊙ surrounded by a lower density envelope of molecular gas. The impinging Ly-c photons induce the propagation of an ionization front into the globule. The evaporation of the ionized gas forms a thin layer of density ne = 1 − 2 × 10 3 cm around the globule, which could be mapped with the VLA. The globule is illuminated mainly on its rear side, by a FUV field of intensity G0 ≃ 1000. It creates a Photon-Dominated Region (PDR) below the surface, which was mapped and characterized with the ISOCAM Circular Variable Filter and the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory. The physical conditions derived from the analysis of the far-infrared lines [OI] 63μm, 145μm and [CII] 158μm, and the continuum emission are in good agreement with some Laboratoire d’Astrophysique, Observatoire de Grenoble, BP 53, F-38041, Grenoble Cedex 9, France [email protected] Consejo Superior de Investigaciones Cient́ıficas, Instituto de Estructura de la Materia, Serrano 121, E-28006 Madrid Instituto de Astronomı́a, UNAM, Campus Morelia, A.P. 3-72, Morelia, Mich. 58089, México ENS, LRA, 24 rue Lhomond, Paris, France Max-Planck Institut für Extra-Terrestrische Physik, 85741 Garching, Germany ESTEC/SCI-SAF, P.O. Box 209, NL-2200 AG Noordwijk The Netherlands