AST/RO Observations of Atomic Carbon near the Galactic Center

Abstract

We present a coarsely sampled map of the region |l| ≤ 2°, |b| ≤ 0°1 in the 492 GHz (³P₁ → ³P₀) fine-structure transition of neutral carbon, observed with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). The distribution of [C I] emission is similar on the large scale to that of CO J = 1 → 0. On average, the ratio of the integrated intensities, I[C I]/I¹²ᴄᴏ, is higher in the Galactic disk than in the Galactic center region. This result is accounted for by the absorption of ¹²CO within the clouds located in the outer Galactic disk. The ratio I[C I]/I¹²ᴄᴏ is surprisingly uniform over the variety of environments near the Galactic center. On average, [C I] is optically thin [or as optically thin as ¹³CO (J = 1 → 0)], even in the dense molecular clouds of the Galactic center region.