A Class I and Class II CH3OH Maser Survey of EGOs from the GLIMPSE Survey

• Published in: The Astrophysical journal 2009, Vol.702 (2), p.1615-1647
• Main Authors: Cyganowski, C. J, Brogan, C. L, Hunter, T. R, Churchwell, E
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/702/2/1615

We present the results of a high angular resolution Very Large Array (VLA) Class I 44 GHz and Class II 6.7 GHz CH3OH maser survey of a sample of ~20 massive young stellar object (MYSO) outflow candidates selected on the basis of extended 4.5 Delta *mm emission in Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images. These 4.5 Delta *mm selected candidates are referred to as extended green objects (EGOs), for the common coding of this band as green in three-color Infrared Array Camera images. The detection rate of 6.7 GHz Class II CH3OH masers, which are associated exclusively with massive YSOs, toward EGOs is 64%-nearly double the detection rate of surveys using other MYSO selection criteria. The detection rate of Class I 44 GHz CH3OH masers, which trace molecular outflows, is ~89% toward EGOs associated with 6.7 GHz CH3OH masers. The two types of CH3OH masers exhibit different spatial distributions: 6.7 GHz masers are centrally concentrated and usually coincide with 24 Delta *mm emission, while 44 GHz masers are widely distributed and generally trace diffuse 4.5 Delta *mm features. We also present results of a complementary James Clerk Maxwell Telescope (JCMT) single-pointing molecular line survey of EGOs in the outflow tracers HCO+(3-2) and SiO(5-4). The HCO+ line profiles and high SiO detection rate (90%) are indicative of the presence of active outflows. No 44 GHz continuum emission is detected at the 5 mJy beam-1 (5 Delta *s) level toward 95% of EGOs surveyed, excluding bright ultracompact H II regions as powering sources for the 4.5 Delta *mm outflows. The results of our surveys constitute strong evidence that EGOs are young, massive YSOs, with active outflows, presumably powered by ongoing accretion.