Particle and Flames in Radiative and Magnetic Flows

October 11-15, 2010
Lyon, France

Contribution of Kengo Tomida


Formation, Evolution and Observability of low-mass First cores


"Stellar structure and evolution"


Star Formation, RMHD, Protostellar collapse, Radiation Transfer, ALMA


The first core is a hydrostatict object which is first formed in the early phase of low mass star formation process. However, fourty years have passed since Larson (1969) theoretically proposed this object, but it has never been confirmed due to its observational difficulty, that is, the lifetime is fairly short and it is very deeply obscured in the gas envelope. Although it is a transient object, the first core plays a crucial role in the star formation process. The typical angular momentum and magnetic flux of the initial cloud core are too large compared to those of the resulting main sequence star, and redistribution of the angular momentum and magnetic flux is sometimes considered to happen during the first core phase. MHD simulations show the bipolar molecular outflow is also driven just outside the first core by the magnetic Lorentz force. The first core will continuously evolve into circumstellar or protoplanetary discs. Therefore the first core is critically important because it will give us direct evidence to constrain and understand the star formation process if we could observe it. We study the early-phase of low mass star formation process, especially focusing on the properties of first cores. Using our nested-grid self-gravitational RMHD simulation code, we investigated the formation and evolution of the first core without assuming artificial thermal evoltuion track. Since RMHD simulation gives us realistic temperature distribution, our RMHD results can be directly compared with the observation via the post-processing radiation transfer calculation or observational visualization. We show the characteristics of the first core in the RMHD simulation and discuss its observational possibilities.