Distortion of Magnetic Fields in a Starless Core III: Polarization--Extinction Relationship in FeSt 1-457

The relationship between dust polarizationand extinctionwas determined for the cold dense starless molecular cloudcore FeSt 1-457 based on the background star polarimetryof dichroic extinctionat near-infrared wavelengths. Owing to the known (three-dimensional) magnetic field structure, the observed polarizationsfrom the core were corrected by considering (a) the subtraction of the ambient polarizationcomponent, (b) the depolarization effect of inclined distorted magnetic fields, and (c) the magnetic inclination angle of the core. After these corrections, a linear relationship between polarizationand extinctionwas obtained for the core in the range up to $A_V \approx 20$ mag. The initial polarizationvs. extinctiondiagram changed dramatically after the corrections of (a) to (c), with the correlation coefficient being refined from 0.71 to 0.79. These corrections should affect the theoretical interpretation of the observational data. The slope of the finally obtained polarization-- extinctionrelationship is $P_H / E_{H-K_s} = 11.00 \pm 0.72$ $\%$ ${\rm mag}^{-1}$, which is close to the statistically estimated upper limit of the interstellar polarizationefficiency (Jones 1989). This consistency suggests that the upper limit of interstellar polarizationefficiency might be determined by the observational viewing angletoward polarized astronomical objects.