The Distribution of Star Formation and Metals in the Low Surface Brightness Galaxy UGC 628

TL;DR

This study investigates the spatial distribution of star formation and metallicity in the low surface brightness galaxy UGC 628 using multiwavelength observations, revealing clustered star formation and metallicity gradients that inform galaxy evolution.

Contribution

It provides the first spatially-resolved optical spectra analysis of UGC 628, combining emission-line diagnostics to understand star formation and metallicity distribution in low surface brightness galaxies.

Findings

Star formation is highly clustered and mostly occurs in the outer disk.

Metallicity is around log(O/H) = -4.2, higher near the edges.

Current star formation mode has persisted for a long time.

Abstract

We introduce the MUSCEL Program (MUltiwavelength observations of the Structure, Chemistry and Evolution of LSB galaxies), a project aimed at determining the star-formation histories of low surface brightness galaxies. MUSCEL utilizes ground-based optical spectra and space-based UV and IR photometry to fully constrain the star-formation histories of our targets with the aim of shedding light on the processes that led low surface brightness galaxies down a different evolutionary path from that followed by high surface brightness galaxies, such as our Milky Way. Here we present the spatially-resolved optical spectra of UGC 628, observed with the VIRUS-P IFU at the 2.7-m Harlen J. Smith Telescope at the McDonald Observatory, and utilize emission-line diagnostics to determine the rate and distribution of star formation as well as the gas-phase metallicity and metallicity gradient. We find highly clustered star formation throughout UGC 628, excluding the core regions, and a log(O/H) metallicity around -4.2, with more metal rich regions near the edges of the galactic disk. Based on the emission-line diagnostics alone, the current mode of star formation, slow and concentrated in the outer disk, appears to have dominated for quite some time, although there are clear signs of a much older stellar population formed in a more standard inside-out fashion.