MHD simulations of dense core collision

Abstract

We investigated the effect of magnetic fields on the collision process between dense molecular cores. We performed three-dimensional magnetohydrodynamic simulations of collisions between two self-gravitating cores using the Enzo adaptive mesh refinement code. The core was modeled as a stable isothermal Bonnor-Ebert (BE) sphere immersed in uniform magnetic fields. Collisions were characterized by the offset parameter $b$, Mach number of the initial core $\mathcal{M}$, magnetic field strength $B_0$, and angle $\theta$ between the initial magnetic field and collision axis. For head-on ($b=0$) collisions, one protostar was formed in the compressed layer. The higher the magnetic field strength, the lower the accretion rate. For models with $b=0$ and $\theta =90^{\circ }$, the accretion rate was more dependent on the initial magnetic field strength compared with $b=0$ and $\theta =0^{\circ }$ models. For off-center ($b=1$) collisions, the higher specific angular momentum increased; therefore, the gas motion was complicated. In models with $b=1$ and $\mathcal{M}=1$, the number of protostars and gas motion highly depended on $B_0$ and $\theta$. For models with $b=1$ and $\mathcal{M}=3$, no significant shock-compressed layer was formed and star formation was not triggered.

arXiv comment20 pages, 18 figures, 3 tables. Accepted for publication in ApJ

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• Gas and star kinematics in cloud-cloud collisions
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