A survey of the Galactic center region in HCO+, H13CO+ and SiO

Abstract

Aims: A large scale survey of the Galactic center region in he 3 mm rotational transitions of SiO, HCO+ and H13CO+ (beamsize ~ 3. 6 arcmin) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry and other properties. Methods: Using the NANTEN 4m telescope from Nagoya University, a region between -5.75<l<5.6 (degree) and -0.68<b<1.3 (degree) was mapped in the J=1-0 lines of HCO+ and H13CO+ and in the J=2-1 line of SiO with a spacing of 3.75 arcmin (HCO+) and 1.875 arcmin (SiO and H13CO+). Results: Velocity channel maps, longitude-velocity maps and latitude-velocity maps are presented. We identify 51 molecular clouds; 33 of them belong to the Galactic center, and 18 to disk gas. We derive an average of the luminosity ratio of SiO(J=2-1)/CO(J=1-0) in clouds belonging to the Galactic center of 4.9x10^{-3} and for disk clouds of 3.4x 10^{-3}. The luminosity ratio of HCO^+(J=1-0)/CO(J=1\to0) in the Galactic Center is 3.5x 10^{-2}, and for disk clouds is 1.5x 10^{-2}. We can distinguish clearly between regions where the SiO or HCO+ are dominating.