Major Mergers as Possible Drivers of the Galaxy Mass Assembly in the Early Universe: New Insights from ALMA Observations

Abstract

Galaxies are thought to grow through star formation or by interacting with each other. To understand which process dominates, we investigated the contribution of major mergers to the galaxy mass assembly across cosmic time. We made use of recent observations from the ALPINE survey to analyze the morphology and kinematic information provided by the [CII] 158 μm line observed in z∼5 star-forming galaxies. We found that 40% of galaxies in that epoch were undergoing merging. By combining our results with studies at lower redshift, we computed the cosmic evolution of the merger fraction, estimating that major mergers could contribute up to 30% to the cosmic star-formation rate density at z>4.

Keywords

• galaxies: evolution
• galaxies: formation
• galaxies: high redshift
• early universe