Circum-nuclear eccentric gas flow in the Galactic Center revealed by ALMA CMZ Exploration Survey (ACES)

TL;DR

This study uses ALMA observations of CS line emissions to reveal that dense gas in the Galactic Center follows eccentric orbits, providing insights into the gravitational potential of the inner 10 parsecs.

Contribution

It presents the first detailed analysis of eccentric gas flow in the Galactic Center using high-resolution ALMA data, highlighting the orbit of a dense gas cloud as a tracer of the inner gravitational potential.

Findings

Eccentric orbital structure of dense gas in the Galactic Center.

Identification of G0.02 as a kinematic tracer of the inner potential.

Evidence of noncircular gas motion in the central 10 pc.

Abstract

We analyze the CS (J=2-1) line cube from the internal data release obtained by the large-scale program "ALMA CMZ Exploration Survey (ACES)" to investigate the kinematic structure of the innermost $\sim 10$ pc region of the Galaxy, which contains the high-velocity compact cloud (HVCC) at $(l,b,v_{\rm lsr})\sim(+0^\circ.02,-0^\circ.02, 100 {\rm km~s}^{-1})$ (hereafter G0.02). The longitude-velocity diagram (LVD) of the cloud draws an elliptical structure, which is interpreted as an orbital trajectory in the $(l,V_{\rm lsr})$ space of a noncircular (eccentric) motion of the molecular gas in the gravitational potential of an extended mass distribution in the central 10 pc of the Galaxy. We argue that G0.02 is a kinematic tracer of the inner potential, a rare case of a dense gas following an eccentric orbit in the nuclear gravitational field.