Induced formation of primordial low-mass stars

We show that the explosion of the first supernovae can trigger low-mass star formation via gravitational fragmentation of the supernova-driven gas shell. If the shell mass does not exceed the host galaxy gas mass, all explosions with energies ESN>=1051 erg can lead to shell fragmentation. However, the minimum ambient density required to induce such fragmentation is much larger, n0>300 cm-3, for Type II supernovae than for pair-instability ones, which can induce star formation even at lower ambient densities. The typical mass of the unstable fragments is ~104-7Msolar their density is in the range 110-6 7107 cm-3. Fragments have a metallicity strictly lower than 10-2.6Zsolar and large values of the gravitational-to-pressure force ratio f~=8. Based on these findings, we conclude that the second generation of stars produced by such self-propagating star formation is predominantly constituted by low-mass, long-living, extremely metal-poor (or even metal-free, if mixing is suppressed) stars. We discuss the implications of such results for Pop III star formation scenarios and for the most iron-poor halo star HE0107-5240