Molecular clouds and clumps in the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey

TL;DR

This paper presents a comprehensive catalog of molecular clouds and clumps in the inner Galaxy based on 13 CO emission data from the BU-FCRAO GRS, enabling detailed analysis of their properties and star formation activity.

Contribution

It provides the first homogeneous, fully-sampled 13 CO survey of the Galactic Ring, identifying over 800 molecular clouds and 6000 clumps with detailed property analysis.

Findings

Clouds inside the 5 kpc ring are warmer and denser.

Clouds within the ring have larger areas and more clumps.

The catalog aids in studying molecular cloud structure and star formation.

Abstract

The Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS) of 13 CO (1-0) emission covers Galactic longitudes 18 deg < l < 55.7 deg and Galactic latitudes |b| <= 1 deg. Using the SEQUOIA array on the FCRAO 14m telescope, the GRS fully sampled the 13 CO Galactic emission (46 arcsec angular resolution on a 22 arcsec grid) and achieved a spectral resolution of 0.21 km/s. Because the GRS uses 13 CO, an optically thin tracer, rather than 12 CO, an optically thick tracer, the GRS allows a much better determination of column density and also a cleaner separation of velocity components along a line of sight. With this homogeneous, fully-sampled survey of 13 CO, emission, we have identified 829 molecular clouds and 6124 clumps throughout the inner Galaxy using the CLUMPFIND algorithm. Here we present details of the catalog and a preliminary analysis of the properties of the molecular clouds and their clumps. Moreover, we compare clouds inside and outside of the 5 kpc ring and find that clouds within the ring typically have warmer temperatures, higher column densities, larger areas, and more clumps compared to clouds located outside the ring. This is expected if these clouds are actively forming stars. This catalog provides a useful tool for the study of molecular clouds and their embedded young stellar objects.