The SIGNALS from HII Regions

In this invited review, I present an overview of H II regions and their central role in our understanding of galactic ecosystems. I begin with a brief introduction to the fundamental physics of ionized nebulae, outlining the processes that govern emission line formation and structure. From there, I explore what we can learn observationally from H II regions, including how their emission lines allow us to diagnose ionization conditions and excitation mechanisms via diagnostic tools like the BPT diagram. I discuss the distribution of H II regions across this parameter space and the physical drivers behind their location on such diagrams. The talk then focuses on chemical abundance measurements and how these measurements trace the evolutionary history and current state of teh host galaxy. I conclude by highlighting several promising directions for future work within the SIGNALS collaboration, leveraging the unprecedented size and resolution of the dataset to address outstanding questions in star formation, feedback, and chemical enrichment.

May 20, 2025 — May 23, 2025