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Extended mid-infrared emission around the outflow source and the compact H II region in AFGL 4029 *
A. Zavagno 1,
P.O. Lagage 2 and
S. Cabrit 3
Received 7 September 1998 / Accepted 21 January 1999
We present the first sub-arsecond 8-13 µm images of the young stellar cluster AFGL 4029, obtained using the camera CAMIRAS mounted at the Canada-France-Hawaii Telescope.
The two dominant components of the cluster, a highly obscured young stellar object (YSO) and a compact H II region excited by a B1 star, are both spatially resolved and show the 11.3 µm band in emission. The dust composition and excitation in the AFGL 4029 H II region appear similar to those in other compact H II regions of moderate excitation observed by ISO-SWS. In addition, we observe that the 11.3 µm feature/continuum ratio decreases toward the main exciting star on scales 8800 AU. The large extent of the mid-infrared emission from the YSO is so far a unique example among deeply embedded objects. It suggests that there is no simple trend relating the mid-IR size and the evolutionary status in young stars. The emission arises in optically thin circumstellar dust, possibly in a cavity carved by the bipolar outflow.
An optical and near-infrared reflection nebulosity present 5" away from the YSO is also detected in the mid infrared. It is particularly bright in the 11.3 µm feature, with a feature/continuum ratio 4 comparable to that seen in prototypical reflection nebulae. Finally, mid-IR emission associated with an optical jet knot in the same zone suggests that shocks, by creating small particles, might explain the high surface brightness in this region.
Key words: stars: imaging stars: individual: AFGL 4029 stars: pre-main sequence infrared: ISM: continuum infrared: ISM: lines and bands infrared: stars
Send offprint requests to: A. Zavagno (Zavagno@obmara.cnrs-mrs.fr; Lagage@cea.fr; Cabrit@mesioq.obspm.fr)
Online publication: March 18, 1999