Triggered Star Formation and the Creation of the Supergiant HI Shell in IC 2574

TL;DR

This study uses Hubble Space Telescope imaging to show that stellar feedback created a large HI shell in IC 2574 and triggered subsequent star formation, revealing the dynamic interplay between stellar activity and interstellar medium structures.

Contribution

It provides detailed star formation history and evidence linking stellar feedback to the formation of a supergiant HI shell in a dwarf galaxy.

Findings

Stellar feedback created a ~1 kpc HI shell in IC 2574.

Two major star formation episodes occurred 200-300 Myr and ~25 Myr ago.

Stellar feedback likely caused the shell and triggered new star formation.

Abstract

Based on deep imaging from the Advanced Camera for Surveys aboard the Hubble Space Telescope, we present new evidence that stellar feedback created a ~ 1 kpc supergiant HI shell (SGS) and triggered star formation (SF) around its rim in the M81 Group dwarf irregular galaxy IC 2574. Using photometry of the resolved stars from the HST images, we measure the star formation history of a region including the SGS, focusing on the past 500 Myr, and employ the unique properties of blue helium burning stars to create a movie of SF in the SGS. We find two significant episodes of SF inside the SGS from 200 - 300 Myr and ~ 25 Myr ago. Comparing the timing of the SF events to the dynamic age of the SGS and the energetics from the HI and SF, we find compelling evidence that stellar feedback is responsible for creating the SGS and triggering secondary SF around its rim.