Rotation and stability of the circumnuclear gas disk in the Galactic Center potential by the ALMA CMZ Exploration Survey (ACES)

TL;DR

This study uses ALMA data to analyze the shape, rotation, and stability of the gas disk near the Galactic Center, revealing a nearly spherical potential, a cusp-like mass distribution, and implications for star formation suppression.

Contribution

It provides the first detailed modeling of the Galactic Center's gravitational potential and mass distribution based on molecular line data, highlighting the disk's stability and star formation conditions.

Findings

Potential is approximately spherical within 20 pc

Mass density follows a cusp profile with index -1.9

Gas disk is stable against self-gravity within ~14 pc

Abstract

We investigated the gravitational potential and mass distribution in the Galactic Center by examining the morphology and kinematics of the circumnuclear gaseous disk revealed by the molecular line data from the ALMA CMZ Exploration Survey (ACES). We obtain an estimate of the shape of the potential {within the central $\sim 20$ pc} to reproduce the observed properties of the circumnuclear gas disk (CND) by simulating the motion of test particles for various axial ratios and show that the potential is approximately spherical. We construct a rotation curve by applying the terminal velocity method to the position-velocity diagrams, and calculate the mass distribution in the Galactic Center. The distribution of mass density is found to be of cusp type, approximated by $\rho_{\rm mass} \sim 1.56\times 10^5(R/1 {\rm pc})^{-1.9}~M_{\odot} {\rm pc}^{-3}$, where $R$ is the distance from the nucleus. We discuss the tidal effect caused by the gravitational potential that produces the rotation curve and show that the gas disk is stable against self-gravitational contraction within a critical radius of $ R_{\rm T}\sim 14 ~(\rho_{\rm gas}/10^5 {\rm H_2~cm^{-3}})^{-1/2}~{\rm pc}$. This suggests suppression of star formation and a top-heavy IMF in the circmunuclear region.