HCO+ Clouds in the SGR b2 Region

Abstract

The HCO^+ 1--0 transition line was observed toward the Sgr B2 region in our Galactic center. We found that there exist two large-scale velocity structures of vlsr ˜50 and ˜100 km/s, which are thought to interact with each other. A new gas clump ``OF28 Cloud" (`Odenwald & Fazio FIR 38' Cloud), showing different chemical and kinematical properties with the Sgr B2(M) cloud, was found in the 50 km/s gas component. Toward the core of this component, we derive the HCO^+ total column density, N(HCO^+) = (2-5)×10^14 cm-2 and the mass M =1 × 10^6 M⊙, by estimating its size, ˜15pc, from the half-power width of this component. We also found that there is a highly turbulent component in this region in the velocity range of about 100 km s-1. The column density of this component is N(HCO^+) = 1 × 10^13 cm-2. The HCO^+ in this region may form effectively by the reaction between C^+ and OH, which are the elements whose abundances increase rapidly in shocked region.

Keywords

• SM
• interstellar molecule: HCO+
• galactic center
• Sgr B2