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

TL;DR

This survey maps the Galactic center region in specific molecular lines to analyze cloud conditions, chemistry, and heating, revealing differences between Galactic center and disk clouds.

Contribution

It provides the first large-scale mapping of the Galactic center in HCO+, H13CO+, and SiO, offering new insights into molecular cloud properties and chemical distinctions.

Findings

Identified 51 molecular clouds, 33 in the Galactic center and 18 in the disk.

Measured luminosity ratios of SiO/CO and HCO+/CO, showing regional differences.

Distinguished regions dominated by SiO or HCO+ indicating varied chemical environments.

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.