A census of 163 large-scale (>=10 pc), velocity-coherent filaments in inner Galactic plane: physical properties, dense gas fraction, and association with spiral arms

TL;DR

This study systematically identifies and analyzes 163 large-scale, velocity-coherent filaments in the inner Galactic plane, revealing their physical properties, distribution, and relationship with spiral arms, with implications for star formation.

Contribution

It introduces a novel minimum spanning tree algorithm for filament identification and provides a comprehensive analysis of their properties and Galactic distribution.

Findings

Dense gas mass fraction is similar across Galactic positions and spiral arms.

Most filaments are inter-arm, with minor differences between arm and inter-arm filaments.

Clump mass at the same size shows no significant difference on or off filaments.

Abstract

The interstellar medium has a highly filamentary and hierarchical structure, which may play a significant role in star formation. A systematical study on the large-scale filaments towards their physical parameters, distribution, structures and kinematics will inform us of what kind of filaments have potential to form stars, how the material feed protostars through filaments, and the connection between star formation and Galactic spiral arms. Unlike the traditional "by eyes" searches, we use a customized minimum spanning tree algorithm to identify filaments by linking Galactic clumps from the APEX Telescope Large Area Survey of the Galaxy catalogue. In the inner Galactic plane ($|l| < 60^\circ$), we identify 163 large-scale filaments with physical properties derived, including dense gas mass fraction, and compare them with an updated spiral arm model in position-position-velocity space. Dense gas mass fraction is found not to differ significantly in various Galactic position, neither does it in different spiral arms. We also find that most filaments are inter-arm filaments after adding a distance constraint, and filaments in arm differ a little with those not in. One surprising result is that clumps on and off filaments have no significant distinction in their mass at the same size.