OGHReS: Large-scale filaments in the outer Galaxy

TL;DR

This study reveals the presence of large-scale filaments in the outer Galaxy using high-resolution CO data, showing they are linked to inter-arm regions and have lower masses compared to inner Galaxy filaments, providing insights into Galactic dynamics and star formation.

Contribution

The paper demonstrates the existence of large-scale filaments in the outer Galaxy and characterizes their properties, expanding understanding of Galactic structure beyond the inner regions.

Findings

37 filaments identified in the outer Galaxy

Filaments are associated with inter-arm regions

Lower masses compared to inner Galaxy filaments

Abstract

Filaments are a ubiquitous morphological feature of the molecular interstellar medium and are identified as sites of star formation. In recent years, more than 100 large-scale filaments (with a length $>10$\,pc) have been observed in the inner Milky Way. As they appear linked to Galactic dynamics, studying those structures represents an opportunity to link kiloparsec-scale phenomena to the physics of star formation, which operates on much smaller scales. In this letter, we use newly acquired Outer Galaxy High Resolution Survey (OGHReS) $^{12}$CO(2-1) data to demonstrate that a significant number of large-scale filaments are present in the outer Galaxy as well. The 37 filaments identified appear tightly associated with inter-arm regions. In addition, their masses and linear masses are, on average, one order of magnitude lower than similar-sized molecular filaments located in the inner Galaxy, showing that Milky Way dynamics is able to create very elongated features in spite of the lower gas supply in the Galactic outskirts.