12CO (3-2) High-Resolution Survey (COHRS) of the Galactic Plane: Complete Data Release

TL;DR

The COHRS survey provides high-resolution, comprehensive 12CO (3-2) data of the inner Galactic plane, enabling detailed studies of molecular clouds and spiral structures, with improved data reduction and integration with other surveys.

Contribution

This paper releases the complete, high-resolution COHRS dataset with enhanced data processing, facilitating advanced analysis of Galactic molecular structures and comparison with other CO surveys.

Findings

Data covers 9.5° to 62.3° in Galactic longitude and |b| ≤ 0.5°

Integrated-emission and PV maps match spiral-arm structures

Comparison of 12CO (1-0) and (3-2) distributions with star-forming regions

Abstract

We present the full data release of 12CO (3-2) High-Resolution Survey (COHRS), which has mapped the inner Galactic plane over the range of 9.5$^{\circ}$ $\le$ l $\le$ 62.3$^{\circ}$ and $|b| \le 0.5^{\circ}$. The COHRS has been carried out using the Heterodyne Array Receiver Program (HARP) on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The released data are smoothed to have a spatial resolution of 16.6 arcsec and a velocity resolution of 0.635 km/s, achieving a mean root-mean-square of $\sim 0.6$ K on $T_\mathrm{A}^*$. The COHRS data are useful for investigating detailed three-dimensional structures of individual molecular clouds and large-scale structures such as spiral arms in the Galactic plane. Furthermore, data from other available public surveys of different CO isotopologues and transitions with similar angular resolutions to this survey, such as FUGIN, SEDIGISM, and CHIMPS/CHIMPS2, allow studying the physical properties of molecular clouds and comparing their states with each other. In this paper, we report further observations on R2 and improved data reduction since the original COHRS release. We discuss the characteristics of the COHRS data and present integrated-emission images and a position-velocity (PV) map of the region covered. The PV map shows a good match with the spiral-arm traces from the existing CO and HI surveys. We also obtain and compare integrated one-dimensional distributions of 12CO (1-0) and (3-2) and those of star-forming populations to each other.