Magnetohydrodynamics of population III star formation

Jet-driving and fragmentation processes in a collapsing primordial cloud are studied using three-dimensional MHD nested grid simulations. Starting from a rotating magnetized spherical cloud with a number density of n(c) similar or equal to 10(3) cm(-3), we follow the evolution of the cloud until the adiabatic core (or protostar) formation epoch, n(c) similar or equal to 10(22) cm(-3). We calculate 36 models parameterizing the initial magnetic gamma(0) and rotational beta(0) energies. The evolution of collapsing primordial clouds is characterized by the ratio of the initial rotational energy to the magnetic energy, gamma(0)/beta(0). The Lorentz force significantly affects cloud evolution when gamma(0) > beta(0), while the centrifugal force dominates the Lorentz force when beta(0) > gamma(0). When the cloud rotates rapidly with an angular velocity of Omega(0) > 10(-17)(n(c)/10(3) cm(-3))(2/3) s(-1) and beta(0) > gamma(0), fragmentation occurs before protostar formation, but no jet appears after protostar formation. On the other hand, when the initial cloud has a magnetic field of B(0) > 10(-9)(n(c)/10(3) cm(-3))(2/3) G and gamma(0) > beta(0), a strong jet appears after protostar formation without fragmentation. Our results indicate that Population III protostars frequently show fragmentation and protostellar jets. Population III stars are therefore born as binary or multiple stellar systems; as in present-day star formation, they can drive strong jets that disturb the interstellar medium significantly, and thus they may induce the formation of next-generation stars.