The neutral-gas disk around the galactic center

The mapping of far-infrared C(+) and O(0) fine-structure lines and the first detection of far-infrared CO and OH rotational line emission and OH absorption toward the Galactic center are reported. These measurments are compared with far-infrared and radio continuum maps, with recent observations of the 12.8 micron forbidden Ne II line, and with measurements of CO 2.6 mm emission and H I 21 cm absorption. The new observations clearly show that there is a 10 pc diameter neutral gas disk or torus of several times 10,000 solar masses surrounding the inner ionized cavity. The disk has an inner radius of 1.7 pc, is inclined by about 20 deg to the Galactic plane, and may be quite thin. The atomic gas in the neutral disk is dense and fills less than 10 percent of the volume. The disk rotates about the Galactic center about an axis remarkably similar to that of the Galactic rotation at much larger scales.