EMISSION MECHANISM OF 'GREEN FUZZIES' IN HIGH-MASS STAR-FORMING REGIONS
- Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
- Department of Physics, National Tsing Hua University, 101 Section 2 Kuang Fu Road, Hsinchu 30013, Taiwan (China)
- Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)
The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has revealed that a number of high-mass protostars are associated with extended mid-infrared emission, particularly prominent at 4.5 {mu}m. These are called 'Green Fuzzy' emission or 'Extended Green Objects'. We present color analysis of this emission toward six nearby (d = 2-3 kpc) well-studied high-mass protostars and three candidate high-mass protostars identified with the Spitzer GLIMPSE survey. In our color-color diagrams, most of the sources show a positive correlation between the [3.6]-[4.5] and [3.5]-[5.8] colors along the extinction vector in all or part of the region. We compare the colors with those of scattered continuum associated with the low-mass protostar L 1527, modeled scattered continuum in cavities, shocked emission associated with low-mass protostars, modeled H{sub 2} emission for thermal and fluorescent cases, and modeled polycyclic aromatic hydrocarbon (PAH) emission. Of the emission mechanisms discussed above, scattered continuum provides the simplest explanation for the observed linear correlation. In this case, the color variation within each object is attributed to different foreground extinctions at different positions. Alternative possible emission mechanisms to explain this correlation may be a combination of thermal and fluorescent H{sub 2} emission in shocks, and a combination of scattered continuum and thermal H{sub 2} emission, but detailed models or spectroscopic follow-up are required to investigate this possibility further. Our color-color diagrams also show possible contributions from PAHs in two objects. However, none of our samples show clear evidence for PAH emission directly associated with the high-mass protostars, several of which should be associated with ionizing radiation. This suggests that these protostars are heavily embedded even at mid-infrared wavelengths.
- OSTI ID:
- 22016203
- Journal Information:
- Astrophysical Journal, Vol. 748, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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