Three dimensional ( 3D ) magnetic field information on molecular clouds and cores is important for revealing their kinematical stability ( magnetic support ) against gravity which is fundamental for studying the initial conditions of star formation .
In the present study , the 3D magnetic field structure of the dense starless core FeSt 1-457 is determined based on the near-infrared polarimetric observations of the dichroic polarization of background stars and simple 3D modeling .
With an obtained angle of line-of-sight magnetic inclination axis \theta _ { inc } of 45 ^ { \circ } \pm 10 ^ { \circ } and previously determined plane-of-sky magnetic field strength B _ { pol } of 23.8 \pm 12.1 \mu { G } , the total magnetic field strength for FeSt 1-457 is derived to be 33.7 \pm 18.0 \mu { G } .
The critical mass of FeSt 1-457 , evaluated using both magnetic and thermal/turbulent support is { M } _ { cr } = 3.70 \pm 0.92 { M } _ { \odot } , which is identical to the observed core mass , M _ { core } = 3.55 \pm 0.75 { M } _ { \odot } .
We thus conclude that the stability of FeSt 1-457 is in a condition close to the critical state .
Without infalling gas motion and no associated young stars , the core is regarded to be in the earliest stage of star formation , i.e. , the stage just before the onset of dynamical collapse following the attainment of a supercritical condition .
These properties would make FeSt 1-457 one of the best starless cores for future studies of the initial conditions of star formation .