The Inner 200pc: Hot Dense Gas

We present fully-sampled maps of 461GHz CO J = 4 → 3, 807GHz CO J = 7 → 6, and 492GHz [CI]³P₁ → ³P₀ emission from the inner 3 degrees of the Galactic Center region taken with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) in 2001-2002. The data cover -1°.3 < ℐ < 2°, -0°.3 < b < 0°.2 with 0.5′ spacing, resulting in spectra in 3 transitions at over 24,000 positions on the sky. The CO J = 4 → 3 emission is found to be essentially coextensive with lower-J transitions of CO. The CO J = 7 → 6 emission is spatially confined to a far smaller region than the lower-J CO lines. The [CI] ³P₁ → ³P₀ emission has a spatial extent similar to the low-J CO emission, but is more diffuse. Bright CO J = 7 → 6 emission is detected in the well-known Galactic Center clouds SgrA and SgrB. Analyzing our CO J = 7 → 6 and CO J = 4 → 3 data in conjunction with J = 1 → 0 ¹²CO and ¹³CO data previously observed with the Bell Laboratories 7-m antenna, we apply a Large Velocity Gradient (LVG) model to estimate the kinetic temperature and density of molecular gas in the inner 200 pc of the Galactic Center region. Typical pressures in the Galactic Center gas are n(H₂) · T_kin ∼ 10^5.2 Kcm^-3. We present an (ℐ, b) map of molecular hydrogen column density derived from our LVG results.