Near-infrared imaging survey of young stellar objects in BOK globules
1994; Institute of Physics; Volume: 108; Linguagem: Inglês
10.1086/117095
ISSN1538-3881
Autores Tópico(s)Advanced Combustion Engine Technologies
ResumoWe performed a near-infrared imaging survey toward 34 Bok globules containing Infrared Astronomy Satellite (IRAS) point sources, which were young stellar objects (YSOs) candidates. We used state-of-the-art NICMOS 3 and SQIID cameras for this survey. Visual examination of the images revealed that 20 globules showed evidence of nebular emission or very red stellar objects located at the position of the YSO candidates. The IRAS 12/25 micrometers spectral indices of these 20 objects are distinctively different from those of the 14 globules which showed no nebulosity, in the sense that more than 50 percent of the 20 nebular or very red objects have negative IRAS 12/25 micrometers spectral indices, while only 20 percent of the 14 non-nebular objects show such red IRAS colors. Analysis of the near-infrared nebulosities present in the images revealed the following: (1) these nebulosities generally contain a stellarlike source surrounded by an extended component; (2) several possible binaries with separations of about 10" were found to reside in common infrared nebulosity; (3) infrared reflection nebulae, seen at 2.2 micrometers, are good tracers of CO mass outflow morphology. The group of objects displaying nebulosities, when ordered by their increasing 12/25 micrometers indices, seems to form an evolutionary sequence. Large negative 12/25 micrometers indices seem to indicate objects deeply embedded in their clouds (by showing nebulosities mostly in the K band, having associated molecular outflows, and no optical counterparts). As these objects reach later stages of their pre-main-sequence evolution (by showing nebulosity in the J band only, no detected molecular outflow, and having optical counterparts or optical nebulae), their 12/25 micrometers increase and become positive.
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