DEEP VERY LARGE ARRAY RADIO CONTINUUM SURVEYS OF GLIMPSE EXTENDED GREEN OBJECTS (EGOs)

Journal Article · Sat Dec 10 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/743/1/56· OSTI ID:22004520

Cyganowski, C J ^[1]; Brogan, C L; Hunter, T R ^[2]; Churchwell, E ^[3]

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1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
2. NRAO, 520 Edgemont Rd, Charlottesville, VA 22903 (United States)
3. Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States)

We present the results of deep, high angular resolution Very Large Array surveys for radio continuum emission toward a sample of 14 GLIMPSE Extended Green Objects (EGOs). Identified as massive young stellar object (MYSO) outflow candidates based on their extended 4.5 {mu}m emission in Spitzer images, the EGOs in our survey sample are also associated with 6.7 GHz Class II and/or 44 GHz Class I CH{sub 3}OH masers. No continuum is detected at 3.6 or 1.3 cm toward the majority (57%) of our targets (median rms {approx}0.03 and 0.25 mJy beam{sup -1}). Only two EGOs are associated with optically thin emission consistent with ultracompact/compact H II regions. Both of these sources exhibit cm-{lambda} multiplicity, with evidence that one of the less-evolved members may be driving the 4.5 {mu}m outflow. Most of the other cm-{lambda} EGO counterparts are weak ({approx}<1 mJy), unresolved, undetected at 1.3 cm, and characterized by intermediate spectral indices consistent with hypercompact (HC) H II regions or ionized winds or jets. One EGO centimeter (cm) counterpart, likely an optically thick HC H II region, is detected only at 1.3 cm and is associated with hot core line emission and H{sub 2}O and 6.7 GHz CH{sub 3}OH masers. The results of our exceptionally sensitive survey indicate that EGOs signify an early stage of massive star formation, before photoionizing feedback from the central MYSO significantly influences the (proto)cluster environment. Actively driving outflows (and so, presumably, actively accreting), the surveyed EGOs are associated with significant clump-scale gas reservoirs, providing sufficient material for sustained, rapid accretion.

• OSTI ID: 22004520
• Journal Information: Astrophysical Journal, Vol. 743, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTROPHYSICS
IMAGES
MASERS
METHANOL
STAR EVOLUTION
STARS