Imaging study of NGC 3372, the Carina nebula - II. Evidence of activity in the complex Trumpler 14/Car I photodissociation region

TAPIA, M., PERSI, P., BOHIGAS, J., ROTH, M., GOMEZ, M.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2006 p. 513 - 526

0035-8711

We present the results of an imaging survey, from the optical to the mid-infrared, of the dark cloud associated with Car I, a dense cloud that is subject to an intense ultraviolet radiation field from the rich stellar cluster Trumpler 14. New ground-based broad- and narrow-band near-infrared and narrow-band optical images are analysed in combination with archived Spitzer/InfraRed Array Camera (IRAC) images to study this photodissociation region (PDR) and the triggering of a new generation of stars within the cloud, particularly close to its edges. Evidence is given of a clumpy morphology of the dense cloud. The ionization/dissociation front is delineated at the edges of these clumps. The existence of a number of embedded low- to intermediate-mass pre-main-sequence objects is confirmed by their considerable infrared excesses arising from discs and/or detectable X-ray emission. Most of the young stellar objects (YSOs) are located on or just behind ionization fronts, though a few are also outside the cloud. The infrared properties of the YSOs are discussed. Two Class I objects stand out, one of them is an FU Orionis system candidate that had an outburst of more than 3 mag in K between 1993 and 2003, with further evidence that it occurred in the 2000-02 period. Molecular hydrogen line filamentary emission behind the Balmer and Brackett lines along the ionization front is seen delineating the edges of the dense cloud. This emission is also seen in all IRAC images. The diffuse, filamentary emission is very similar in all four 3.6, 4.5, 5.8 and 8 micron bands, though there seem to be subtle differences. Across a bright section of the ionization/dissociation front, we found that, within the observational uncertainties, the maximum emission in all four IRAC channels coincides with that of H2 2.12 micron. The western, embedded, dissociation front close to the CO peak (Car I-W) is seen delineated by a bright, long bar of emission in the 3-12 micron images, in the Midcourse Space Experiment bands A and C and also in radio continuum and hydrogen line emission. These occur in the vicinity of a region of previously reported strong [CI], [CII] and [OI] emission, tracers of PDRs. A few bright, compact knots of H_2 emission, some possibly associated with [SII] emission, are found within the cloud. These may be shock-excited.