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Published online by Cambridge University Press: 04 August 2017
High velocity OH was detected in absorption in several star forming regions. The supersonic OH shows similar bipolar geometry as the CO. The absorbing OH appears to trace the part of the outflows with the highest velocities and lower densities, and provides information on the structure of the outflows at large distances from the central source. At scales of 0.1 to 0.5 parsecs the outflows are elongated in the direction of the steepest density gradient in the ambient cloud. The transitions in the supersonic OH are markedly subthermal (Tex < 3.8 K), since the radiation that is being absorbed is the cosmic background plus a small galactic contribution. We propose a cooling mechanism for the OH analogous to the adiabatic magnetic cooling of paramagnetic salts used in low temperature physics. Magnetic cooling is a potentially important mechanism for astrophysics.