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Astron. Astrophys. 344, 499-504 (1999)

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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

1 Observatoire de Marseille, 2 Place Le Verrier, F-13248 Marseille Cedex 4, France
2 DSM/DAPNIA Service d'Astrophysique, CEA/Saclay, F-91191 Gif-sur-Yvette cedex, France
3 Observatoire de Paris, DEMIRM, URA 336 du CNRS, 61 Avenue de l'Observatoire, F-75014 Paris, France

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 [FORMULA] 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 [FORMULA] 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

* Based on observations made at the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique, and University of Hawaii

Send offprint requests to: A. Zavagno (Zavagno@obmara.cnrs-mrs.fr; Lagage@cea.fr; Cabrit@mesioq.obspm.fr)

© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999