2026/07/23 by Guangwen Chen, J. Alfonso L. Aguerri, Carlos del Burgo +1
#astro-ph.GA
Compact galaxies represent a key population for understanding galaxy evolution, but the relative role of internal structure and environment in shaping their origin remains unclear. We aim to investigate how the abundance and quenching of compact galaxies depend on environment, and to determine whether their formation is governed by a single evolutionary pathway or multiple channels. We analyse a large sample of galaxies in the nearby Universe (z<0.05) with stellar masses in the range 8.2<log(M_⋆/M_\odot)<10.5, comparing compact and control populations as a function of local overdensity. We find that the environmental dependence of compact galaxies is non-monotonic, with two characteristic overdensities, the transition overdensity (δt) and the critical overdensity (δc), defining three distinct regimes. Below δt, compact galaxies are relatively more abundant than the control population, while between δt and δc their relative abundance decreases significantly. Above δc, compact galaxies become increasingly overabundant again. The environmental trends show a strong stellar-mass dependence, with low-mass galaxies exhibiting the strongest deficit at intermediate overdensities and high-mass galaxies dominating the excess population above δc. In addition, the red galaxy fraction increases with local overdensity and is systematically higher in compact galaxies. Our results support a unified evolutionary framework in which compact galaxies do not arise from a single evolutionary channel, but instead reflect multiple pathways whose relative importance depends strongly on stellar mass and environment. Low-mass compact galaxies are closely linked to environmentally driven transformation, whereas high-mass compact galaxies occur across all environments and become increasingly overabundant in the densest regions.