Relative alignment between gas structures and magnetic field in Orion A at different scales using different molecular gas tracers

¹ Department of Astronomy, School of Physics, Peking University, Beijing, 100871, PR China
² Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
e-mail: kwang.astro@pku.edu.cn
³ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁴ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, PR China

Received: 8 January 2024
Accepted: 27 February 2024

Abstract

Context. Magnetic fields can play a crucial role in high-mass star formation. Nonetheless, the significance of magnetic fields at various scales and their relationship with gas structures have been largely overlooked.

Aims. Our goal is to examine the relationship between the magnetic field and molecular gas structures within the Orion A giant molecular cloud at different scales and density regimes.

Methods. We assessed the gas intensity structures and column densities in Orion A using ¹²CO, ¹³CO, and C¹⁸O from Nobeyama observations. By comparing Nobeyama observations with Planck polarization observations on large scales (~0.6 pc) and JCMT polarization observations on small scales (~0.04 pc), we investigate how the role of magnetic fields changes with scale and density.

Results. We find a similar trend from parallel to perpendicular alignment with increasing column density in Orion A at both large and small spatial scales. In addition, when changing from low-density to high-density tracers, the relative orientation preference changes from random to perpendicular. The self-similar results at different scales indicate that magnetic fields are dynamically important in both cloud formation and filament formation. However, magnetic field properties at small scales are relative complicated, and the interplay between magnetic field and star-forming activity needs to be discussed case by case.