Maser Emission toward the Infrared Dark Cloud G359.94+0.17 Seen in Silhouette against the Galactic Center

TL;DR

This study reports strong methanol maser emission and other molecular lines in the infrared dark cloud G359.94+0.17, revealing active star formation in a previously unreported region near the Galactic center.

Contribution

First detection of intense methanol maser emission in G359.94+0.17, indicating active star formation in this infrared dark cloud near the Galactic center.

Findings

Strong 44 GHz CH3OH maser emission (~50 Jy) detected.

Presence of weak 22 GHz H2O maser and 43 GHz SiO thermal emissions.

Cloud composed of two velocity components, with masers associated with the 15 km/s component.

Abstract

The infrared dark cloud G359.94+0.17 is a conspicuous, opaque cloud, which is seen in silhouette against the Galactic center. We found unexpectedly strong (~50 Jy) maser emission of CH3OH at 44 GHz with additional weak 22 GHz H2O maser and 43 GHz SiO thermal emissions toward this cloud. Detections of these molecular lines indicate that strong star forming activities are proceeding in this cloud, which were not reported previously despite of numerous works toward the Galactic center. The line profiles of the NH3 inversion lines at 23 GHz indicate that G359.94+0.17 is composed of mainly two clouds with V(lsr)= 0, and 15 km/s overlapped on the line of sight. The maser emission is associated with the 15 km/s cloud, suggesting that it is located at the Norma spiral arm.