Large-scale velocity-coherent filaments in the SEDIGISM survey: Association with spiral arms and the fraction of dense gas

¹ Department of Astronomy, School of Physics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR China
² Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR China
e-mail: kwang.astro@pku.edu.cn
³ School of Physics & Astronomy, Cardiff University, Queen’s building, The parade, Cardiff CF24 3AA, UK
⁴ Department of Physics and Astronomy, California State University, Sacramento, 6000 J Street, Sacramento, CA 95819-6041, USA
⁵ School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
⁶ Observatorio Astronómico Nacional (OAN, IGN), Calle Alfonso XII 3, 28014 Madrid, Spain
⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁸ Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
⁹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁰ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
¹¹ School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
¹² Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DB, UK
¹³ Space Science Institute, 4765 Walnut St. Suite B, Boulder CO 80301, USA
¹⁴ School of Science and Technology, University of New England, Armidale NSW 2351, Australia
¹⁵ National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China

Received: 23 December 2022
Accepted: 11 May 2023

Abstract

Context. Filamentary structures in the interstellar medium are closely related to star formation. It is possible that the dense gas mass fraction (DGMF) or clump formation efficiency in large-scale filaments determine whether or not they end up hosting star formation activity.

Aims. We aim to automatically identify large-scale filaments, as well as characterizing them, investigating their association with Galactic structures, and studying their DGMFs.

Methods. We used a modified minimum spanning tree (MST) algorithm to chain parsec-scale ¹³CO clumps previously extracted from the Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium (SEDIGISM) survey. The MST connects nodes in a graph such that the sum of edge lengths is at a minimum. A modified MST also ensures the velocity coherence between nodes, so that the identified filaments are coherent in position-position-velocity (PPV) space.

Results. We generated a catalog of 88 large-scale (>10 pc) filaments in the inner Galactic plane (with −60° < l < 18° and |b| < 0.5°). These SEDIGISM filaments are larger and less dense than MST filaments previously identified from the Bolocam Galactic Plane Survey (BGPS) and the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). We find that eight of the filaments run along spiral arms and can be regarded as the “bones” of the Milky Way. We also found three bones associated with the Local spur in PPV space. By compiling 168 large-scale filaments with available DGMF across the Galaxy, namely, an order of magnitude more than previously investigated, we find that DGMFs are not correlated with Galactic location. We also find that bones have higher DGMFs than other filaments.