Stellar Populations and the Star Formation Histories of LSB Galaxies: V. WFC3 Color-Magnitude Diagrams

TL;DR

This study uses WFC3 imaging to analyze the stellar populations and star formation histories of three nearby low surface brightness galaxies, revealing similarities to irregular galaxies and evidence of ongoing star formation.

Contribution

First detailed color-magnitude diagrams of these LSB galaxies, showing their star formation patterns and stellar compositions compared to Local Volume dwarfs.

Findings

Star formation follows patterns seen in irregular galaxies.

Higher proportion of blue main sequence stars than typical dwarfs.

Evidence of constant star formation over the last 100 Myrs.

Abstract

We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et. al LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W and F814W allow the construction of the V-I color-magnitude diagrams (CMD) to M_I = -2. Overall 1869, 465 and 501 stellar sources are identified in the three LSB galaxies F415-3, F608-1 and F750-V1. The spatial distribution of young blue stars matches the H-alpha maps from ground-based imaging, indicating that star formation in LSB galaxies follows the same style as in other irregular galaxies. Several star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The color-magnitude diagrams for each LSB galaxy has the similar morphology to Local Volume (LV) dwarf galaxies, i.e. a blue main sequence, blue and red He burning branches and asymptotic giant branch (AGB) stars. The LSB CMD's distinguish themselves from nearby dwarf CMD's by having a higher proportional of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below -0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V-I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U-V and V-I CMD indicate a history of constant star formation for the last 100 Myrs.