  We have measured the Zeeman splitting of OH megamaser emission at 1667 MHz
from five (ultra)luminous infrared galaxies ([U]LIRGs) using the 305 m Arecibo
telescope and the 100 m Green Bank Telescope. Five of eight targeted galaxies
show significant Zeeman-splitting detections, with 14 individual masing
components detected and line-of-sight magnetic field strengths ranging from
~0.5-18 mG. The detected field strengths are similar to those measured in
Galactic OH masers, suggesting that the local process of massive star formation
occurs under similar conditions in (U)LIRGs and the Galaxy, in spite of the
vastly different large-scale environments. Our measured field strengths are
also similar to magnetic field strengths in (U)LIRGs inferred from synchrotron
observations, implying that milligauss magnetic fields likely pervade most
phases of the interstellar medium in (U)LIRGs. These results provide a
promising new tool for probing the astrophysics of distant galaxies.
