A survey of low surface brightness dwarf galaxies to detect H I-rich companions

We have conducted a survey for H I-rich companions in the vicinity of low surface brightness (LSB) dwarf galaxies, objects that are characterized by low rates of massive star formation. This survey complements our earlier survey of dwarf galaxies exhibiting high star formation rates (H II galaxies). Four of the 17 LSB dwarfs in the sample have nearby, H I-rich companions, and a total of five companions were detected. The companion frequency is therefore p = 0.24, and we determine a lower limit on the true rate of 0.08. This is a much lower rate of occurrence than was detected around the H II galaxies, p = 0.57, which implies a lower limit of p > 0.37. Because the two surveys were carried out under nearly identical circumstances, this difference is genuine and not the result of any relative bias between the two samples. That H rr galaxies have companions more than twice as often as LSB dwarfs provides evidence that the bursts of massive star formation in H II galaxies are being triggered by galaxy-galaxy interactions.