Letter to the Editor

The filamentary structures in the CO emission toward the Milky Way disk

¹ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: soler@mpia.de
² Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
³ Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305, USA
⁴ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁵ Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
⁶ Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Qixia District, Nanjing 210033, PR China

Received: 17 May 2021
Accepted: 16 June 2021

Abstract

We present a statistical study of the filamentary structure orientation in the CO emission observations obtained in the Milky Way Imaging Scroll Painting survey in the range 25_.°8 < l < 49_.°7, |b| ≤ 1_.°25, and −100 < v_LSR < 135 km s⁻¹. We found that most of the filamentary structures in the ¹²CO and ¹³CO emission do not show a global preferential orientation either parallel or perpendicular to the Galactic plane. However, we found ranges in Galactic longitude and radial velocity where the ¹²CO and ¹³CO filamentary structures are parallel to the Galactic plane. These preferential orientations are different from those found for the HI emission. We consider this an indication that the molecular structures do not simply inherit these properties from parental atomic clouds. Instead, they are shaped by local physical conditions, such as stellar feedback, magnetic fields, and Galactic spiral shocks.