Galaxy populations and evolution in clusters. III. The origin of low-mass galaxies in clusters: Constraints from stellar populations

Low-mass galaxies in nearby clusters are the most numerous galaxy type in the universe, yet their origin and properties remain largely unknown. To study basic questions concerning these galaxies we present the results of a survey designed to constrain the characteristics and properties of the stellar populations in a magnitude-complete sample of low-mass cluster galaxies (LMCGs) in the center of the Perseus Cluster. Using deep, high-quality WIYN UBR images to obtain photometric and structural properties, we demonstrate that the 53 LMCGs in our sample have a significant scatter about the color-magnitude relationship at M-B > -15. By comparing single-burst stellar population models with our photometry, we argue that stellar populations in LMCGs all have ages greater than 1 Gyr, with redder LMCGs containing stellar metallicities [Fe/H] > -0.5. By assuming that the colors of LMCGs reflect metallicity and have coevolved with the giant elliptical galaxies, we find a wide range of values, from solar to [Fe/H] about -3. We argue from this that LMCGs have multiple origins and fundamentally differ from Local Group dwarf spheroidal or elliptical galaxies. The inferred lower metallicities of the bluer LMCGs imply that these are possibly primordial galaxies formed through self-enrichment and stellar feedback provided by winds from supernovae. We also investigate several other formation scenarios for these LMCGs, including self-enrichment induced by the confinement of metals in halos by the intracluster medium, in situ formation out of intracluster gas, systems with extreme dark halos, and remnants of previously higher mass systems. We conclude that roughly half of all low-mass cluster galaxies in the center of Perseus have stellar populations and kinematic properties, as discussed in previous papers in this series, consistent with being the remnants of stripped galaxies accreted into clusters several gigayears ago.