2011ApJ...729..124C

We present high angular resolution Submillimeter Array and Combined Array for Research in Millimeter-wave Astronomy observations of two GLIMPSE Extended Green Objects (EGOs)–massive young stellar object (MYSO) outflow candidates identified based on their extended 4.5 µm emission in Spitzer images. The millimeter observations reveal bipolar molecular outflows, traced by high-velocity ¹²CO(2-1) and HCO⁺(1-0) emission, coincident with the 4.5 µm lobes in both sources. SiO(2-1) emission confirms that the extended 4.5 µm emission traces active outflows. A single dominant outflow is identified in each EGO, with tentative evidence for multiple flows in one source (G11.92-0.61). The outflow driving sources are compact millimeter continuum cores, which exhibit hot core spectral line emission and are associated with 6.7 GHz Class II CH₃ OH masers. G11.92-0.61 is associated with at least three compact cores: the outflow driving source, and two cores that are largely devoid of line emission. In contrast, G19.01-0.03 appears as a single MYSO. The difference in multiplicity, the comparative weakness of its hot core emission, and the dominance of its extended envelope of molecular gas all suggest that G19.01-0.03 may be in an earlier evolutionary stage than G11.92-0.61. Modeling of the G19.01-0.03 spectral energy distribution suggests that a central (proto)star (M ∼ 10 M_☉) has formed in the compact millimeter core (M_gas∼12-16 M_☉), and that accretion is ongoing at a rate of ∼10^–3 M_☉/year. Our observations confirm that these EGOs are young MYSOs driving massive bipolar molecular outflows and demonstrate that considerable chemical and evolutionary diversity are present within the EGO sample.