Methanol Maser Emission from Galactic Center Sources with Excess 4.5 μm Emission

Abstract

We present a study of signatures of on-going star formation in a sample of protostellar objects with enhanced 4.5 μm emission ('green' sources) near the Galactic center. To understand how star formation in the Galactic center region compares to that of the Galactic disk, we used the Expanded Very Large Array to observe radiatively excited Class II 6.7 GHz CH3OH masers and collisionally excited Class I 44 GHz CH3OH masers, both tracers of high-mass star formation, toward a sample of 34 Galactic center and foreground 'green' sources. We find that 33\pm15% of Galactic center sources are coincident with 6.7 GHz masers, and that 44\pm17% of foreground sources are coincident with 6.7 GHz masers. For 44 GHz masers, we find correlation rates of 27\pm13% and 25\pm13% for Galactic center green sources and foreground green sources, espectively. Based on these CH3OH maser detection rates, as well as correlations of green sources with other tracers of star formation, such as 24 μm emission and infrared dark clouds (IRDCs), we find no significant difference between the green sources in the Galactic center and those foreground to it. This suggests that once the star formation process has begun, the environmental differences between the Galactic center region and the Galactic disk have little effect on its observational signatures. We do find, however, some evidence that may support a recent episode of star formation in the Galactic center region.

73 pages, 34 figures, 5 tables. Accepted for publication in ApJ

References in corpus (8)

• 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
• Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive YSOs
• The 6-GHz Multibeam Maser Survey I. Techniques
• The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region
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Cited by in corpus (11)

• Online Database of Class I Methanol Masers
• A Census of Early Phase High-Mass Star Formation in the Central Molecular Zone
• Early stage massive star formation near the Galactic Center: Sgr C
• High-mass star-forming cloud G0.38+0.04 in the Galactic Center Dust Ridge contains H2CO and SiO masers
• A 95 GHz Class I Methanol Maser Survey Toward A Sample of GLIMPSE Point Sources Associated with BGPS Clumps
• A search for 95 GHz class I methanol masers in molecular outflows
• A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molecular Zone
• A Spitzer Space Telescope survey of massive young stellar objects in the G333.2-0.4 giant molecular cloud
• Star Formation Sites toward the Galactic Center Region: The Correlation of CH3OH Masers, H2O Masers, and Near-IR Green Sources
• Milliarcsecond structure of water maser emission in two young high-mass stellar objects associated with methanol masers
• Maser Emission toward the Infrared Dark Cloud G359.94+0.17 Seen in Silhouette against the Galactic Center