Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

TL;DR

This study maps molecular gas streamers feeding the circumnuclear disk of the Galactic Center, revealing their role in channeling material toward the supermassive black hole, which enhances understanding of SMBH accretion processes.

Contribution

It presents the first wide-field CS(2-1) map showing dense molecular streamers connecting ambient clouds to the CND, suggesting a mechanism for gas feeding from 20 pc to 2 pc.

Findings

Detection of dense molecular streamers connecting clouds to the CND.

Streamers show rotation and inward motion towards the SMBH.

Gas velocities increase as material approaches the CND.

Abstract

The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2-pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides an unique opportunity to study SMBH accretion at sub-parsec scales. Our new wide-field CS(2-1) map toward the Galactic center (GC) reveals multiple dense molecular streamers originated from the ambient clouds 20-pc further out, and connecting to the central 2 parsecs of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up co-rotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.