The identification of filaments on far infrared and submillimiter images. Morphology, physical conditions and relation with star formation of filamentary structure

TL;DR

This study develops an unbiased method using the Hessian matrix to identify and analyze filamentary structures in molecular clouds, revealing their properties and connection to star formation from Herschel observations.

Contribution

Introduces a novel Hessian matrix-based approach for unbiased filament detection and characterization in molecular cloud images from Herschel data.

Findings

Identified ~500 filaments with lengths up to 30 pc and widths up to 2.5 pc.

Filaments contain most dense material and are linked to star-forming cores.

Surface densities in filaments suggest they are crucial for high-mass star formation.

Abstract

Observations of molecular clouds reveal a complex structure, with gas and dust often arranged in filamentary rather than spherical geometries. The associations of pre- and proto- stellar cores with the filaments suggest a direct link with the process of star formation. Any study of the properties of such filaments requires a representative samples from different enviroments and so an unbiased detection method. We developed such an approach using the Hessian matrix of a surface-brightness distribution to identify filaments and determine their physical and morphological properties. After testing the method on simulated, but realistic filaments, we apply the algorithms to column-density maps computed from Herschel observations of the Galactic Plane obtained by the Hi-GAL project. We identified ~500 filaments, in the longitude range of l=216.5 to l=225.5, with lengths from ~1 pc up to ~30 pc and widths between 0.1 pc and 2.5 pc. Average column densities are between 10^20 cm^-2 and 10^22 cm^-2. Filaments include the majority of dense material with N_H_2 > 6x10^21cm^-2. We find that the pre- and proto-stellar compact sources already identified in the same region are mostly associated with filaments. However, surface densities in excess of the expected critical values for high-mass star formation are only found on the filaments, indicating that these structures are necessary to channel material into the clumps. Furthermore, we analyze the gravitational stability of filaments and discuss their relationship with star formation.