Identification of molecular clouds in emission maps: a comparison between methods in the \ce{^{13}CO}/\ce{C^{18}O} ($J=3-2$) Heterodyne Inner Milky Way Plane Survey

Abstract

The growing range of automated algorithms for the identification of molecular clouds and clumps in large observational datasets has prompted the need for the direct comparison of these procedures. However, these methods are complex and testing for biases is often problematic: only a few of them have been applied to the same data set or calibrated against a common standard. We compare the Fellwalker method, a widely used watershed algorithm, to the more recent Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES). SCIMES overcomes sensitivity and resolution biases that plague many friends-of-friends algorithms by recasting cloud segmentation as a clustering problem. Considering the \ce{^{13}CO}/\ce{C^{18}O} ($J=3-2$) Heterodyne Inner Milky Way Plane Survey (CHIMPS) and the CO High-Resolution Survey (COHRS), we investigate how these two different approaches influence the final cloud decomposition. Although the two methods produce largely similar statistical results over the CHIMPS dataset, FW appears prone to over-segmentation, especially in crowded fields where gas envelopes around dense cores are identified as adjacent, distinct objects. FW catalogue also includes a number of fragmented clouds that appear as different objects in a line-of-sight projection. In addition, cross-correlating the physical properties of individual sources between catalogues is complicated by different definitions, numerical implementations, and design choices within each method, which make it very difficult to establish a one-to-one correspondence between the sources.

accepted MNRAS

References in corpus (21)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Structural Analysis of Molecular Clouds: Dendrograms
• Physical properties of molecular clouds for the entire Milky Way disk
• ATLASGAL --- properties of a complete sample of Galactic clumps
• Bias-free Measurement of Giant Molecular Cloud Properties
• Kinematic Distances to Molecular Clouds identified in the Galactic Ring Survey
• The Nature of the Dense Core Population in the Pipe Nebula: Thermal Cores Under Pressure
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) I: Project Overview and Initial Results
• FellWalker - a Clump Identification Algorithm
• The Perils of Clumpfind: The Mass Spectrum of Sub-structures in Molecular Clouds
• Turbulence sets the initial conditions for star formation in high-pressure environments
• ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy
• The integrated properties of the molecular clouds from the JCMT CO(3-2) High Resolution Survey
• The Mass-Size Relation and the Constancy of GMC Surface Densities in the Milky Way
• Star formation scales and efficiency in Galactic spiral arms
• An Observational Method to Measure the Relative Fractions of Solenoidal and Compressible Modes in Interstellar Clouds
• Physical and chemical differentiation of the luminous star-forming region W49A - Results from the JCMT Spectral Legacy Survey
• G-virial: Gravity-based structure analysis of molecular clouds
• The CARMA-NRO Orion Survey: Statistical Signatures of Feedback in the Orion A Molecular Cloud
• An Observational Perspective of Low-Mass Dense Cores I: Internal Physical and Chemical Properties