Accretion in Gravitationally Contracting Clouds

Accretion flow in a contracting magnetized isothermal cloud was studied usingmagnetohydrodynamical simulations and a nested grid technique. First, theinterstellar magnetized cloud experiences a ``runaway collapse'' phase, inwhich the central density increases drastically within a finite time scale.Finally, it enters an accretion phase, in which inflowing matter accretes ontoa central high-density disk or a new-born star. We found that the accretionrate reaches (4 -- 40) $\times c_s^3/G$, where $c_s$ and $G$ represent theisothermal sound speed and the gravitational constant, respectively. This ismuch larger than the standard accretion rate of $0.975c_s^3/G$ for ahydrostatic isothermal spherical cloud (Shu 1977, AAA19.065.044). Due to theeffect of an extra infall velocity achieved in the runaway phase ($\sim 2c_s$), the accretion rate is boosted. This rate declines with time in contrastto Shu's solution, but keeps $\gtsim 2.5 c_s^3/G$. The observed gas infall ratearound proto-stars such as L1551 IRS 5 and HL Tau is also discussed.