Star-Forming vs. Quenched Galaxies in Voids: Insights into the Role of Mergers

Abstract

Cosmic voids, the largest under-dense structures in the Universe, are crucial for exploring galaxy evolution. These vast, sparsely populated regions are home to void galaxies -- predominantly gas-rich, star-forming, and blue -- that evolve more slowly than those in denser environments. Additionally, the correlation between galaxy mergers and specific properties of galaxies, such as the star formation rate (SFR), is not fully understood, particularly in these under-dense environments. Quenched void galaxies exhibit high SFRs at high redshifts, significantly decreasing at lower redshifts (z < 0.5). These galaxies have higher dark matter halos than star-forming galaxies across all redshifts, leading to rapid gas consumption. They formed earlier and experienced more major mergers in earlier epochs but fewer recent mergers, resulting in a lack of fresh gas for sustained star formation. Also, star-forming and high-mass quenched void galaxies show higher SFRs in mergers compared to non-merger galaxies. This study highlights that formation time, merger rates, and dark matter halos play a crucial role in the star formation history of void galaxies. Rapid and earlier gas consumption due to earlier formation time and the absence of recent mergers could lead to quenched void galaxies at lower redshifts, providing valuable insights into galaxy evolution in low-density environments.