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

¹ Instituto de Radioastronomía Milimétrica (IRAM), Av. Divina Pastora 7, Local 20, 18012 Granada, Spain
e-mail: riquelme@iram.es
² Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
³ Joint ALMA Observatory, Av. Alonso de Córdova 3107, Vitacura, Santiago de Chile, Chile
⁴ Naval Research Laboratory, Code 7210, Washington, DC 20375, USA

Received: 26 September 2009
Accepted: 7 June 2010

Abstract

Aims. A large-scale survey of the Galactic center region in the 3 mm rotational transitions of SiO, HCO⁺ and H¹³CO⁺ (beamsize ) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry, and other properties.

Methods. Using the NANTEN 4 m telescope from Nagoya University, a region between and 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  (HCO⁺) and (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 4.9  ×  10^-3 and for disk clouds of 3.4  ×  10^-3. The luminosity ratio of HCO ⁺ (J = 1 → 0)/CO(J = 1 → 0) in the Galactic center is 3.5  ×  10^-2, and for disk clouds it is 1.5  ×  10^-2. We can distinguish clearly between regions where the SiO or HCO⁺ dominate.