Observational data for the hourglass-like magnetic field toward the starless dense core FeSt 1-457 were compared with a flux freezing magnetic field model ( Myers et al .
2018 ) .
Fitting of the observed plane-of-sky magnetic field using the flux freezing model gave a residual angle dispersion comparable with the results based on a simple three-dimensional parabolic model .
The best-fit parameters for the flux freezing model were a line-of-sight magnetic inclination angle of \gamma _ { mag } = 35 ^ { \circ } \pm 15 ^ { \circ } and a core center to ambient ( background ) density contrast of \rho _ { c } / \rho _ { bkg } = 75 .
The initial density for core formation ( \rho _ { 0 } ) was estimated to be \rho _ { c } / 75 = 4670 cm ^ { -3 } , which is about one order of magnitude higher than the expected density ( \sim 300 cm ^ { -3 } ) for the inter-clump medium of the Pipe Nebula .
FeSt 1-457 is likely to have been formed from the accumulation of relatively dense gas , and the relatively dense background column density of A _ { V } \simeq 5 mag supports this scenario .
The initial radius ( core formation radius ) R _ { 0 } and the initial magnetic field strength B _ { 0 } were obtained to be 0.15 pc ( 1.64 R ) and 10.8 - 14.6 \mu G , respectively .
We found that the initial density \rho _ { 0 } is consistent with the mean density of the nearly critical magnetized filament with magnetic field strength B _ { 0 } and radius R _ { 0 } .
The relatively dense initial condition for core formation can be naturally understood if the origin of the core is the fragmentation of magnetized filaments .