Observations of [C I] and CO Absorption in Cold, Low-Density Cloud Material toward the Galactic Center Broad-Line Emission

摘要

We report the detection of a deep ~ 3P_1 →~3P_0 (C I) absorption feature at v_LSR = 12 km s~-1 with a line width of 6 km s~-1 toward extended line emission at a distance of 11' from Sgr C. The 492 GHz observations were made with the Antarctic Submillimeter Telescope and Remote Observatory. The absorption feature allows the derivation of lower limits for the C I column density in the cold foreground material. The feature is unlikely to be caused by self-absorption within the [C I]emitting cloud because it is observed over a region at least 4' across and is also seen in emission 22' north of the Galactic plane in ~12CO J = 21.