Physical Contact between the +20 km/s Cloud and the Galactic Circumnuclear Disk

Abstract

This paper reports the discovery of evidence for physical contact between the Galactic circumnuclear disk (CND) and an exterior giant molecular cloud. The central 10 pc of our Galaxy has been imaged in the HCN J=1-0, HCO+ J=1-0, CS J=2-1, H13CN J=1-0, SiO J=2-1, SO N_J=2_3-1_2, and HC3N J=11-10 lines using the Nobeyama Radio Observatory 45 m radio telescope. Based on our examination of the position-velocity maps of several high-density probe lines, we have found that an emission "bridge" may be connecting the +20 km/s cloud (M-0.13-0.08) and the negative-longitude extension of the CND. Analyses of line intensity ratios imply that the chemical property of the bridge is located between the +20 km/s cloud and the CND. We introduce a new interpretation that a part of the CND may be colliding with the 20 km/s cloud and the collision may be responsible for the formation of the bridge. Such collisional events could promote mass accretion onto the CND or into the inner ionized cavity, which may be further tested by proper motion studies.

Accepted for publication in The Astrophysical Journal

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• The Fifth Candidate for an Intermediate-mass Black Hole in the Galactic Center
• Discovery of Two Small High-Velocity Compact Clouds in the Central 10 Parsecs of Our Galaxy
• The Nuclear Filaments inside the Circumnuclear Disk in the Central 0.5 pc of the Galactic center
• Hot Molecular Core Candidates in the Galactic Center 50 km/s Molecular Cloud
• High-spectral resolution M-band observations of CO Rot-Vib absorption lines towards the Galactic center
• Discovery of the Tadpole Molecular Cloud near the Galactic Nucleus