Ultraviolet Imaging Telescope View of Dwarf Irregular Galaxy IC 2574: Is the Star Formation Triggered Due to Expanding H I Shells?

Abstract

Star-forming dwarf galaxies in the local volume are diverse and ideal test beds to understand the details of star formation in a variety of environments. Here we present a deep far-UV ( FUV ) imaging study of the nearby dwarf irregular galaxy IC 2574 using the Ultraviolet Imaging Telescope. We identi fi ed 419 FUV-bright regions with radii between 15 and 285 pc in the galaxy and found that 28.6% of them are located in H

I shells, 12.6% inside holes, and 60.1% away from the holes. The H  I column density is found to be more than 10 21 cm − 2 for 82.3% of the identi fi ed regions. Thirty of the 48 H

I holes show triggered star formation in their shells, while 16 holes do not show any related FUV emission. Cross-matching with H α emission, we found that 23 holes have both FUV and H α emission in their shells, signifying a very recent trigger. Therefore, star formation in the galaxy has been partly triggered due to the expanding H

I holes, whereas in the majority of the sites, it is driven by other mechanisms. Irrespective of the location, larger star-forming complexes were found to have multiple substructures. We report two resolved components for the remnant cluster of the supergiant shell and estimate their masses. The star formation rate of IC 2574 is found to be 0.57 M e yr − 1 , which is slightly higher compared to the average value of other nearby dwarf irregular galaxies.