Herschel Space Telescope showed that molecular clouds universally have filamentary structure (filament hereafter). Also, observational understanding about the structure of magnetic fields (B-fields hereafter) in the filaments has been majorly advanced thanks to the recent detailed dust emission polarimetry using JCMT. This allowed us to discuss not only direction of the B-fields on POS but also 3D structure of it and its dynamical roles in star-formation from polarization properties. For example, there is a suggestion that the 3D structure of B-field in filaments can be estimated from variation in I (total intensity) and PI (polarized intensity), especially the FWHM ratio of I to PI, along minor-axis of filaments (Doi et al. 2021). They discussed about this estimation method with magnetohydrostatic model. We focus on what the FWHM ratio means in the dynamical evolution of turbulent filaments.
First, we performed self-gravitational magnetohydrodynamics simulations of turbulent filament evolution using SFUMATO code. Second, we conducted synthetic observation to our simulation results utilizing RADMC-3D to examine the I and PI profiles along the minor axis of the turbulent filament, following the estimation method of B-fields structure as proposed in Doi et al. 2021. We introduced two angles, inclination angle theta and rotating angle phi, to specify the observation position and investigated the angle dependency of the FWHM ratio distribution in filament .
As a results, we found that the mean and variance of the distribution of the FWHM ratio of I to PI within the filament show a monotonic observation position dependence. This suggests that a broad study of the polarization profile in a filament can quantify its three-dimensional magnetic field structure from these statistics of the FWHM ratio distribution in it.