Interferometric Mapping of Magnetic Fields in Star‐forming Regions. II. NGC 2024 FIR 5

Abstract

We present the —rst interferometric polarization maps of the NGC 2024 FIR 5 molecular core, obtained with the BIMA array at approximately 2A resolution. We measure an average position angle of [60i ^ 6i in the main core of FIR 5 and 54i ^ 9i in the eastern wing of FIR 5. The morphology of the polarization angles in the main core of FIR 5 suggests that the —eld lines are parabolic, with a symmetry axis approximately parallel to the major axis of the putative disk in FIR 5, which is consistent with the theoretical scenario that the gravitational collapse pulled the —eld lines into an hourglass shape. The polarization percentage decreases toward regions with high intensity and close to the center of the core, suggesting that the dust alignment efficiency may decrease at high density. The plane-of-sky —eld strength can be estimated with the modi—ed Chandrasekhar-Fermi formula, and the small dispersion of the polarization angles in FIR 5 suggests that the magnetic —eld is strong mG) and perhaps domi(Z2 nates the turbulent motions in the core. . . . . . .