Abstract
The Sgr A West HII‐region is surrounded by an extended (R≤8–9pc) massive (Md≊2–5 104M0) disk of atomic and molecular gas. The structure’s overall inclination to the line‐of‐sight is ≊70°, and the major axis is tilted against the galactic plane. The thickness of the disk seems supported by turbulent pressure. The dominant large‐scale motion is rotation (vrot≊110 kms−1) about the nucleus. Recent high spatial resolution data reveal that the circumnuclear disk is not a planar equilibrium configuration, but is warped and kinematically perturbed on short timescales (≊105 yr−1).The atomic and molecular line emission arises from an unusually warm (T≊300 K), dense (n≊105 cm−3) and highly turbulent medium that occupies only a small volume of the emission region (fv≤0.1). The excitation of the gas is due to a combination of UV heating, for the atomic phase, and dissipation of turbulent energy in small‐scale low velocity shocks for the bulk of the molecular material.The disk‐like gas distribution may represent a pars...
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