Consistency of Ambipolar Diffusion Models with Infall in the L1544 Protostellar Core

Recent high-resolution studies of the L1544 protostellar core by Tafalla etal. and Williams et al. reveal the structure and kinematics of the gas. Theobservations of this prestellar core provide a natural test for theoreticalmodels of core formation and evolution. Based on their results, the aboveauthors claim a discrepancy with the implied infall motions from ambipolardiffusion models. In this paper, we reexamine the earlier ambipolar diffusionmodels, and conclude that the L1544 core can be understood to be a magneticallysupercritical core undergoing magnetically diluted collapse. We also present anew model specifically designed to simulate the formation and evolution of theL1544 core. This model, which uses reasonable input parameters, yields mass andradial density distributions, as well as neutral and ion infall speed profiles,that are in very good agreement with physical values deduced by observations.The lifetime of the core is also in good agreement with prestellar corelifetimes estimated from statistics of an ensemble of cores. The observationalinput can act to constrain other currently unobserved quantities such as thedegree of ionization, and the background magnetic field strength andorientation near the L1544 core.Comment: 14 pages AAS LaTeX, 5 figures postscript. To appear in the Astrophysical Journal, Vol. 529 #2, 1 Feb 200