# Indication of Another Intermediate-mass Black Hole in the Galactic Center

## TL;DR

This study presents evidence for an intermediate-mass black hole in the Galactic center by observing molecular gas streams with ALMA, revealing their orbital dynamics and ionized gas signatures, implying the presence of a wandering black hole.

## Contribution

It provides the first detailed kinematic evidence for an intermediate-mass black hole in the Galactic center using high-resolution molecular line observations.

## Key findings

- Molecular gas streams orbit a point mass of about 3.2 x 10^4 solar masses.
- Ionized gas indicates shock or photoionization near the orbiting streams.
- High-velocity clouds can serve as probes for quiescent black holes.

## Abstract

We report the discovery of molecular gas streams orbiting around an invisible massive object in the central region of our Galaxy, based on the high-resolution molecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). The morphology and kinematics of these streams can be reproduced well through two Keplerian orbits around a single point mass of $(3.2 \pm 0.6)\times 10^4 \ M_\odot$. We also found ionized gas toward the inner part of the orbiting gas, indicating dissociative shock and/or photoionization. Our results provide new circumstantial evidences for a wandering intermediate-mass black hole in the Galactic center, suggesting also that high-velocity compact clouds can be probes of quiescent black holes abound in our Galaxy.