Emission Mechanism of "Green Fuzzies" in High-mass Star Forming Regions

Abstract

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-micron. 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 H2 emission for thermal and fluorescent cases, and modeled 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 H2 emission in shocks, and a combination of scattered continuum and thermal H2 emission, but detailed models or spectroscopic follow-up are required to further investigate this possibility. Our color-color diagrams also show possible contributions from PAHs in two objects. However, none of our sample 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 those protostars are heavily embedded even at mid-infrared wavelengths.

32 pages, 14 figures, 3 tables, accepted for publication in Astrophysical Journal

References in corpus (20)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• A Catalog of Extended Green Objects (EGOs) in the GLIMPSE Survey: A new sample of massive young stellar object outflow candidates
• A Class I and Class II Methanol Maser Survey of Extended Green Objects (EGOs) from the GLIMPSE Survey
• WFCAM, Spitzer-IRAC and SCUBA observations of the massive star forming region DR21/W75: I. The collimated molecular jets
• The Mid-Infrared Extinction Law in the Ophiuchus, Perseus, and Serpens Molecular Clouds
• Spitzer observations of HH54 and HH7-11: mapping the H2 ortho-to-para ratio in shocked molecular gas
• Spatially Resolved Molecular Hydrogen Emission in the Inner 200AU Environments of Classical T Tauri Stars
• Spitzer IRAC and MIPS Imaging of Clusters and Outflows in 9 High-mass Star Forming Regions
• Outflows from Massive YSOs as Seen with the Infrared Array Camera
• Constraining the Envelope Structure of L1527 IRS: Infrared Scattered Light Modeling
• Molecular Outflows and a Mid-Infrared Census of the Massive Star-Formation Region Associated with IRAS 18507+0121
• The Remarkable Mid-Infrared Jet of Massive Young Stellar Object G35.20-0.74
• Mapping warm molecular hydrogen with Spitzer's Infrared Array Camera (IRAC)
• Spitzer IRAC Detection and Analysis of Shocked Molecular Hydrogen Emission
• Spitzer-IRAC GLIMPSE of high mass protostellar objects. I Infrared point sources and nebulae
• The Rotating Molecular Structures and the Ionized Outflow Associated with IRAS 16547-4247
• An H2CO 6cm Maser Pinpointing a Possible Circumstellar Torus in IRAS18566+0408
• Spitzer imaging of the jet driving the NGC 2264 G outflow
• Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on Massive YSOs
• A Detailed Study of Spitzer-IRAC Emission in Herbig-Haro Objects (II): Interaction Between Ejecta and Ambient Gas

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