Stellar Populations and the Star Formation Histories of LSB Galaxies—Part I: Optical and Hα Imaging

Figure 14

𝐵𝑉𝐼 color plane for the subsample of LSB galaxies with 𝐵−𝑉 and 𝑉−𝐼 colors (black symbols). RC3 galaxies are shown as green symbols. Also shown are 13 Gyrs stellar population tracks (instantaneous burst followed by passive evolution) for a range of metallicities (red) and a 1 Gyr stellar population (blue). Given that the mean metallicity of LSB galaxies is about [Fe/H] = −1.0 [16], there is no old stellar population that fits their 𝐵−𝑉 versus 𝑉−𝐼 colors. Therefore, all indicators are that there must be a significant younger population in LSB galaxies, despite their low stellar density appearance.