A study of two dwarf irregular galaxies with asymmetrical star formation distributions

TL;DR

This study investigates the environmental factors influencing asymmetric star formation in two dwarf irregular galaxies, revealing higher gas pressure and complex gas kinematics in regions of intense star formation.

Contribution

It provides new insights into how external processes and internal gas dynamics contribute to asymmetric star formation in dwarf irregular galaxies.

Findings

Higher gas pressure and density in star-forming regions

Significant deviations from ordered gas rotation

Presence of high velocity dispersion and multiple gas components

Abstract

Two dwarf irregular galaxies DDO 187 and NGC 3738 exhibit a striking pattern of star formation: intense star formation is taking place in a large region occupying roughly half of the inner part of the optical galaxy. We use data on the HI distribution and kinematics and stellar images and colors to examine the properties of the environment in the high star formation rate (HSF) halves of the galaxies in comparison with the low star formation rate (LSF) halves. We find that the pressure and gas density are higher on the HSF sides by 30-70%. In addition we find in both galaxies that the HI velocity fields exhibit significant deviations from ordered rotation and there are large regions of high velocity dispersion and multiple velocity components in the gas beyond the inner regions of the galaxies. The conditions in the HSF regions are likely the result of large-scale external processes affecting the internal environment of the galaxies and enabling the current star formation there.