2006ApJ...636..261H

We obtained the first view in H¹³CO⁺ J=1-0 and a high-resolution map in thermal SiO lines of G0.11-0.11, which is a molecular cloud situated between the Galactic Center radio arc and Sgr A. From a comparison with previous line observations, we found that the H¹³CO⁺ J=1-0 line is optically thin, whereas the thermal SiO lines are optically thick. The line intensity in H¹³CO⁺ J=1-0 shows that the cloud has a large column density, up to N(H₂)=(6-7)x10²³/cm2, which corresponds to about 640-740 mag in A_Vor 10-12 mag in A_25µm. The estimated column density is the largest known of any even in the Galactic center region. We conclude from the intensity ratio of SiO J=1-0 to CS J=1-0 that emitting gas is highly inhomogeneous for SiO abundance on a scale smaller than the beam width ∼35".