Super-rotating protostellar jets

Abstract

Protostellar jets are most striking phenomena in star-forming regions and considered to be an essential ingredient in the star formation process. Stars form in gravitationally collapsing clouds. The mass of protostar at its birth is equivalent to Jovian mass or 0.1 percent of the solar mass. After the birth, the protostar acquires its mass by accreting material from a surrounding rotation disk embedded in an infalling envelope that is a remnant of the natal cloud of the star. Protostellar jets are believed to expel the excess angular momentum from the circumstellar region that allows accretion on to the star. Here, we report the detection of super-rotating jets driven from a protostar FIR 6b (HOPS 60) in Orion Molecular Cloud-2. The jet rotation velocity exceeds 20kms-1 and the specific angular momentum of the jet is as large as ∼ 1022cm2s-1, which hitherto are the largest that have been observed in protostellar jets. The extraordinary large rotation velocity and specific angular momentum can be explained by a magnetohydrodynamic disk wind. This is clear evidence that magnetic fields play a crucial role for protostellar evolution and that angular momentum is removed by protostellar jets.