Letter to the Editor

OGHReS: Large-scale filaments in the outer Galaxy^⋆

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: dcolombo@mpifr-bonn.mpg.de
² Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
³ Commissariat à l’énergie atomique et aux énergies alternatives, 91191 Gif-sur-Yvette, Saclay, France
⁴ Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea
⁵ INAF – Istituto di Radioastronomia and Italian ALMA Regional Centre, via P. Gobetti 101, 40129 Bologna, Italy
⁶ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁷ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, CA, Italy

Received: 8 September 2021
Accepted: 27 October 2021

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) ¹²CO(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.