Discovery of the Tadpole Molecular Cloud near the Galactic Nucleus

TL;DR

This paper reports the discovery of the Tadpole molecular cloud near the Galactic Center, exhibiting unique kinematic features suggestive of an intermediate-mass black hole, based on detailed CO observations and modeling.

Contribution

The study presents the first identification of a peculiar molecular cloud with Keplerian motion indicating a possible intermediate-mass black hole near the Galactic nucleus.

Findings

The Tadpole cloud shows a head-tail structure with a steep velocity gradient.

Kinematic modeling suggests a 10^5 solar mass object at the cloud's center.

Absence of counterparts in other wavelengths supports the black hole hypothesis.

Abstract

In this paper, we report the discovery of an isolated, peculiar compact cloud with a steep velocity gradient at $2\farcm 6$ northwest of Sgr A*. This ``Tadpole'' molecular cloud is unique owing to its characteristic head-tail structure in the position-velocity space. By tracing the CO {\it J}=3--2 intensity peak in each velocity channel, we noticed that the kinematics of the Tadpole can be well reproduced by a Keplerian motion around a point-like object with a mass of $1\!\times\! 10^{5}\,M_{\odot}$. Changes in line intensity ratios along the orbit are consistent with the Keplerian orbit model. The spatial compactness of the Tadpole and absence of bright counterparts in other wavelengths indicate that the object could be an intermediate-mass black hole.