Received; accepted

The dynamical and thermal evolution of a gas shell, swept by supernova in the first-collapsed pregalactic-objects, is discussed with taking into account primordial H2 and HD chemistry and by using the analytical solutions with the explosion energy and the background density in the host clouds as parameters. It is found that the shell can fragment into pieces to trigger star formation since HD molecules form at the fractional abundances of ∼ 10−5 and cool the gas shell down to 30 ∼ 65 K. The Jeans masses in the fragments decrease well below a solar mass before the fragments contract to be optically thick to the H2 and HD lines. Accordingly, low-mass stars, which can survive to date, are expected in the primordial clouds of masses as low as 106M. If the possible mixing with supernova ejecta is taken into account, these low mass stars are likely to be polluted at an average metallicity of [Fe/H] −3 and may have relevance to the extremely metal-poor stars, found in the Galactic Halo. Subject headings: cosmology: theory—early universe—molecular processes— galaxies: formation—stars: formation 1