High-speed molecular cloudlets around the Galactic center's supermassive black hole

Abstract

We present 1″-resolution ALMA observations of the circumnuclear disk (CND) and the interstellar environment around Sgr A∗. The images unveil the presence of small spatial scale12CO (J = 3-2) molecular "cloudlets" (≲ 20 000 AU size) within the central parsec of the Milky Way, in other words, inside the cavity of the CND, and moving at high speeds, up to 300 km s-1 along the line-of-sight. The12CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (vLSR ≲-150 km s-1), more localized and clumpy at extreme positive-velocities (vLSR ≲ +200 km s-1). Based on the pencil-beam12CO absorption spectrum toward Sgr A∗ synchrotron emission, we also present evidence for a diffuse molecular gas component producing absorption features at more extreme negative-velocities (vLSR