An extremely large column density cloud G0.11-0.11 in the Galactic Center Region

Abstract

We obtained the detail map in H13CO+ and in thermal SiO lines of G0.11-0.11, which is a molecular cloud located between the Galactic Center Arc and Sgr A. From line intensity ratios we found H13CO+ line is optically thin, whereas the thermal SiO lines are optically thick for this cloud. The cloud has a large column density up to N(H2) = (6 - 7) × 1023cm−2, which corresponds to about 640 − 740 mag in AV or 10 − 12 mag in A25μm. This is the largest known even in the Galactic Center region. The intensity ratio of SiO to CS lines suggests that emitting gas is highly inhomogeneous for SiO abundance on a scale smaller than the beam with about 35′.