Self-propagating Star Formation in a Turbulent Interstellar Medium

Abstract

We study the propagational properties of sequential star or star-clump formations in the interstellar medium (ISM), introducing the effect of turbulence into the analytic self-propagating star formation (SPSF) model in the form of microscopic random motion. As the result of numerical simulations, we find that on a large scale the star-forming region is transmitted outward from the original location of the star cluster on the random motion of turbulent ISM. By contrast, the self-propagational property contributes largely to the spread of the star-forming regions on a small scale, where the relative velocity of turbulence against the original star clump is small. The characteristic scale length distinguishing the above two propagating properties is estimated to be about 50 pc, beyond which the SPSF timescale exceeds the crossing time of turbulent motion. Moreover, we find that the time delay of sequential star formations against the original one, Δt, correlates to their separations, Δx, as Δt ~ 50 Myr[Δx/(0.5 kpc)]0.5 on the large scale. This is in good agreement with the recently proposed age-separation relation for star clusters in the Large Magellanic Cloud. We argue that globally the age-separation relation is a reminiscence of ISM turbulence, while it reflects the SPSF locally.