Oral Presentation

ALMA views of high-velocity compact clouds in the Galactic center

Author(s): Shunya Takekawa (NAOJ), Tomoharu Oka, Yuhei Iwata, and Shiho Tsujimoto (Keio University)

Presenter: Shunya Takekawa (NAOJ)

High-velocity compact clouds (HVCCs) are a peculiar population of compact molecular clouds with extremely broad velocity widths in the central region of our Galaxy. Approximately one hundred HVCCs have been identified so far. Most of them are associated with no counterparts at other wavelengths, rendering it difficult to understand their origins. Interactions with supernova explosions, cloud-cloud collisions and gravitational interactions with massive compact objects have been suggested as possible explanations for HVCCs. Recently, we have conducted high-resolution molecular line observations of two HVCCs near the Galactic nucleus with ALMA. In these observations, we have discovered gas streams showing clear orbital motions around invisible gravitational sources. The kinematical features and absences of other-wavelength counterparts suggest that the gravitational sources may probably be inactive massive intermediate-mass black holes (IMBHs). Our results provide new circumstantial evidences for wandering IMBHs in the Galactic center. HVCCs may potentially be a key population to search for quiescent black holes.