Methanol Maser Emission from Galactic Center Sources with Excess 4.5 {\mu}m Emission

TL;DR

This study investigates methanol maser emissions from 'green' sources near the Galactic center to compare star formation activity with that in the Galactic disk, finding similar signatures but some evidence of recent star formation in the Galactic center.

Contribution

It provides the first comparative analysis of methanol maser detection rates in Galactic center versus foreground sources, revealing environmental effects on star formation signatures.

Findings

Similar maser detection rates in Galactic center and foreground sources.

No significant difference in star formation signatures between environments.

Evidence of recent star formation activity in the Galactic center.

Abstract

We present a study of signatures of on-going star formation in a sample of protostellar objects with enhanced 4.5 {\mu}m 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 {\mu}m 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.