Star-formation complexes in the 'galaxy-sized' supergiant shell of the galaxy Holmberg I

TL;DR

This study investigates the star formation processes and gas dynamics in Holmberg I, revealing that star formation occurs in large complexes influenced by the supergiant HI shell, with evidence of triggered star formation and shell destruction.

Contribution

It provides detailed kinematic, ionization, and metallicity analysis of Holmberg I's star-forming regions, highlighting the role of the supergiant shell in star formation propagation and galaxy evolution.

Findings

Star formation occurs in large complexes rather than isolated HII regions.

Triggered star formation is evident on multiple scales.

The supergiant shell is being disrupted by star formation activity.

Abstract

We present the results of observations of the galaxy Holmberg I carried out at the Russian 6-m telescope in the narrow-band imaging, long-slit spectroscopy, and scanning Fabry-Perot interferometer modes. A detailed analysis of gas kinematics, ionization conditions, and metallicity of star-forming regions in the galaxy is presented. The aim of the paper is to analyse the propagation of star formation in the galaxy and to understand the role of the ongoing star formation in the evolution of the central 'galaxy-sized' supergiant HI shell (SGS), where all regions of star formation are observed. We show that star formation in the galaxy occurs in large unified complexes rather than in individual giant HII regions. Evidence of the triggered star formation is observed both on scales of individual complexes and of the whole galaxy. We identified two supernova-remnant candidates and one late-type WN star and analysed their spectrum and surrounding-gas kinematics. We provide arguments indicating that the SGS in Holmberg I is destructing by the influence of star formation occurring on its rims.