Interstellar-Cloud Formation in the Extended Envelopes of Blue Compact Dwarf Galaxies

Abstract

Abstract Blue compact dwarf galaxies (BCDs) have an interesting feature in their central region where stars are actively forming. In this paper, we show that shock waves produced by the starbursts there are able to trigger self-gravitating interstellar clouds in extended envelopes, which are often observed in typical BCDs. The criterion adopted for the formation of interstellar clouds is very simple, that is, $\rho \gt 2 \Gamma{\bar{\rho}}/3$. Here, ρ is the gas density of the shocked layer, ${\bar{\rho}}$ is a mean density including the dark matter, and Γ is a numerical factor between 0.5 and 1.0, depending on the mass distribution of the galaxy. Hence, we suggest that the infalling of the clouds onto the central regions causes subsequent starbursts after ∼ 0.1 Gyr of the event, and that the episodic starbursts continue during sub-Gyr.