Papers - INUTSUKA, Shu-ichiro

*An Origin of Supersonic Motions in Interstellar Clouds Reviewed

Hiroshi Koyama, Shu-ichiro Inutsuka

The Astronphysical Journal   Vol. 564 ( 2 ) page： L97-L100   2002.1

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Language：English   Publishing type：Research paper (scientific journal)  

The propagation of a shock wave into an interstellar medium is investigated by two-dimensional numerical hydrodynamic calculation with cooling, heating, and thermal conduction. We present results of the high-resolution, two-dimensional calculations to follow the fragmentation that results from thermal instability in a shock-compressed layer. We find that the geometrically thin cooling layer behind the shock front fragments into small cloudlets. The cloudlets have supersonic velocity dispersion in the warm neutral medium, in which the fragments are embedded as cold condensations. The fragments tend to coalesce and become larger clouds.

*A Radiation Hydrodynamic Model for Protostellar Collapse. II. The Second Collapse and the Birth of a Protostar Reviewed

Hirohiko Masunaga, Shu-ichiro Inutsuka

The Astrophysical Journal   Vol. 351 ( 1 ) page： 350-365   2000.3

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

We carry out radiation hydrodynamic calculations to study physical processes in the formation of a 1 Msolar protostar. Following our previous work, calculations pursue the whole evolution from the beginning of the first collapse to the end of the main accretion phase. The adiabatic core formed after the initial collapse (i.e., the first core) experiences further gravitational collapse triggered by dissociation of molecular hydrogen, which leads to the formation of the second core, i.e., the birth of a protostar. The protostar grows in mass as accreting the infalling material from the circumstellar envelope, while the protostar keeps its radius at ~4 Rsolar during the main accretion phase. These typical features in the evolution are in good agreement with previous studies. We consider two different initial conditions for the density distribution: homogeneous and hydrostatic cloud cores with the same central density of 1.415x10-19 g cm-3 . The homogeneous core has the total mass of 1 Msolar while the hydrostatic core has 3.852 Msolar. For the initially homogeneous model, the accretion luminosity rapidly rises to the maximum value of 25 Lsolar just after the birth of a protostar, and declines gradually as the mass accretion rate decreases. In contrast, the luminosity increases monotonically with time for the initially hydrostatic model. This difference arises because the mass accretion rate varies depending on the inward acceleration at the initial stage, which affects the luminosity curve. A less massive hydrostatic core would possess the similar properties in the luminosity curve to the 3.852 Msolar case, because a hydrostatic cloud core with mass lower than 3.852 Msolar can be shown to provide a smaller mass accretion rate after the birth of a protostar and a more gradual rise in the luminosity curve. Our numerical code is designed to provide the evolution of the spectral energy distribution (SED) along with the dynamical evolution in our spherically symmetric calcu