We present our analysis of the magnetic field structures from 6000 au to 100 au scales in the Class 0 protostar B335 inferred from our JCMT POL-2 observations and the ALMA archival polarimetric data .
To interpret the observational results , we perform a series of ( non- ) ideal MHD simulations of the collapse of a rotating non-turbulent dense core , whose initial conditions are adopted to be the same as observed in B335 , and generate synthetic polarization maps .
The comparison of our JCMT and simulation results suggests that the magnetic field on a 6000 au scale in B335 is pinched and well aligned with the bipolar outflow along the east–west direction .
Among all our simulations , the ALMA polarimetric results are best explained with weak magnetic field models having an initial mass-to-flux ratio of 9.6 .
However , we find that with the weak magnetic field , the rotational velocity on a 100 au scale and the disk size in our simulations are larger than the observational estimates by a factor of several .
An independent comparison of our simulations and the gas kinematics in B335 observed with the SMA and ALMA favors strong magnetic field models with an initial mass-to-flux ratio smaller than 4.8 .
We discuss two possibilities resulting in the different magnetic field strengths inferred from the polarimetric and molecular-line observations , ( 1 ) overestimated rotational-to-gravitational energy in B335 and ( 2 ) additional contributions in the polarized intensity due to scattering on a 100 au scale .