Collapse and fragmentation of a primordial filamentary cloud revisited

Abstract

Gravitational collapse and fragmentation of a filamentary cloud in the context of primordial star formation is reinvestigated. With and without the effect of external far-ultraviolet radiation, dynamical and thermal evolution of a collapsing filament is calculated using one-dimensional numerical hydrodynamics with taking into account non-equilibrium chemical reactions and the photodissociation of molecular hydrogen owing to the external far-ultraviolet radiation. With the effect of the external far-ultraviolet radiation, a filamentary cloud with moderate line mass tends to collapse adiabatically in low density regime (n < 100/cm3). By considering fragmentation in this adiabatic phase in addition to the fragmentation around the loitering point, the effect of external dissociation radiation increases fragment mass.