The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2

Abstract

We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 − 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical.

Magnetic Fields and Fragmentation of Filaments in the Hub of California-X

“…They are mostly associated with active low-to high-mass star clusters (Kumar et al 2020), and easily found both in nearby star-forming molecular clouds and more distant infrared dark clouds. Hence, HFSs have been studied using multiwavelength observations to understand how they form and how stars are generated in them (e.g., Kumar et al 2020;Bhadari et al 2022;Hwang et al 2022).…”

B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). I. The Massive Filament G11.11–0.12 Observed by SOFIA/HAWC+

“…Mapping the B-field strengths has been done only for a few objects: Orion A (Guerra et al 2021;Hwang et al 2021), Monoceros R2 (Hwang et al 2022), and 30 Doradus (Tram et al 2023). Before these studies, the mean values of B-field strengths were only estimated.…”

Filamentary Network and Magnetic Field Structures Revealed with BISTRO in the High-mass Star-forming Region NGC 2264: Global Properties and Local Magnetogravitational Configurations

“…Observationally, magnetic fields are commonly found to correlate with the orientation of interstellar filaments (Heyer et al 2008;Li & Houde 2008;Busquet et al 2013;Palmeirim et al 2013;Planck Collaboration et al 2016;Hwang et al 2022), suggesting that they play an important role in the filament formation. The correlation between filaments and magnetic fields likely varies with column densities along or across filaments (Planck Collaboration et al 2016;Pillai et al 2020;Arzoumanian et al 2021;Kwon et al 2022), implying that the role of the magnetic field possibly evolves locally.…”

“…Recently, new analytical methods have been proposed to extract local properties of magnetic fields. These include the polarization-intensity gradient method (Koch et al 2012a(Koch et al , 2012b(Koch et al , 2013, the histogram of relative orientation (HRO) analysis (Soler et al 2013;Planck Collaboration et al 2016;Soler 2019;Kwon et al 2022), spatial distributions of magnetic field strengths (Wang et al 2020b;Hwang et al 2021Hwang et al , 2022, and relative orientations among gravity, magnetic fields, and density structures (Koch et al 2018(Koch et al , 2022Wang et al 2020aWang et al , 2022. In this paper, we aim at building an analysis scheme highlighting the local physical conditions within HFSs in order to reveal the variations in the role of the magnetic field.…”