Structural properties of cluster galaxies at z ∼ 0.1

We study the galaxy cluster ACO7 to further understand how the size of a galaxy scales with stellar mass. Imaging from the Subaru Hyper Suprime-Cam and spectroscopy from Hectospec enable us to measure the structural parameters (size, axis ratio, and S´ersic index) for 420 galaxies in r-band using GALFIT. We construct the size - stellar mass relation for 136 star-forming galaxies and 226 quiescent galaxies in ACO7 using our size measurements from GALFIT and stellar masses. From this relation, we determine the characteristic size, size of a galaxy with a fiducial mass of 5 × 1010M⊙, of star-forming and quiescent galaxies. We find that quiescent galaxies in the cluster are more likely to inhabit the extreme ends of the size distribution. For star-forming galaxies, we find that within uncertainty, the sizes are larger in clusters compared to the field. This analysis provides insight into how the cluster environment affects the sizes of star-forming and quiescent galaxies.