HOCO+ toward the galactic center

Abstract

We have identified a weak thermal line, U42.767, which has been detected only in the directions toward Sgr A and Sgr B2, astheHOCO+ 2 02-101 transition. Because of the proximity of this line to the SiO maser line at 42.821 GHz (J = 1-0 v = 2), it was observable simultaneously in ∼ 43 GHz SiO maser searches at Nobeyama. From the past data of SiO maser surveys of infrared objects in the Galactic center, we created a map of emission distribution of HOCO+ in the Sgr A molecular cloud as well as maps of the 29SiO J = 1-0 v = 0 thermal emission and H53α emission. The emission distribution of HOCO+ was quite similar to that of 29SiO emission. This suggests that an enhancement of the HOCO+ abundance in the galactic center is induced by shock activities, which release CO2 molecules frozen on grains into gases. © 2006. Astronomical Society of Japan.