研究成果・発表論文

Secondary Star Formation in a Population III Object

Susa, Hajime,   & Umemura, Masayuki


要旨
We explore the possibility of subsequent star formation after a first star forms in a Population III object, by focusing on the radiation-hydrodynamic (RHD) feedback caused by ionizing photons, as well as H$_2$-dissociating photons. For this purpose, we perform three-dimensional RHD simulations in which the radiative transfer of ionizing photons and H$_2$-dissociating photons from a first star is self- consistently coupled with hydrodynamics based on a smoothed particle hydrodynamics method. It is shown that density peaks above a threshold density can keep collapsing, owing to the shielding of H$_2$-dissociating radiation by an H$_2$ shell formed ahead of a D-type ionization front. But, below the threshold density an M-type ionization front with a shock propagates, and density peaks are radiation-hydrodynamically evaporated by the shock. The threshold density depends on the distance from the source star and is åisebox-0.5ex~10$^2$ cm$^-3$ for a source distance of 30 pc. Taking into consideration that the extent of a Population III object is \i̊sebox-0.5ex~100 pc and the density peaks within it have densities of 10$^2$-10$^4$ cm$^-3$, it is concluded that secondary star formation is possible in the broad regions of a Population III object.




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