The $-12$ mag dip in the galaxy luminosity function of Hickson Compact Groups

We present the galaxy luminosity functions (LFs) of four Hickson Compact Groups using image data from the Subaru Hyper Suprime-Cam. A distinct dip appeared in the faint-ends of all the LFs at $M_gsim-12$. A similar dip was observed in the LFs of the galaxy clusters Coma and Centaurus. However, LFs in the Virgo, Hydra, and the field had flatter slopes and no dips. As the relative velocities among galaxies are lower in compact groups than in clusters, the effect of galaxy-galaxy interactions would be more significant in compact groups. The $M_gsim-12$ dip of compact groups may imply that frequent galaxy-galaxy interactions would affect the evolution of galaxies, and the dip in LF could become a boundary between different galaxy populations.