The long road to the Green Valley: Tracing the evolution of the Green Valley galaxies in the EAGLE simulation

TL;DR

This study traces the evolution of Green Valley galaxies from early cosmic times to present day using EAGLE simulations, revealing distinct phases of growth, transition, and quenching driven by internal and environmental factors.

Contribution

It provides a detailed, phase-based evolutionary history of Green Valley galaxies, highlighting the roles of gas dynamics, mergers, and environment in their transformation.

Findings

Three evolutionary phases identified: growth, transition, quenching.

Majority of Green Valley galaxies enter the green valley at z<1.

Approximately 5% of progenitors reenter the green valley after becoming red.

Abstract

We study the evolution of the progenitors of the present-day Green Valley (GV) galaxies across redshift $z=10-0$ using data from the EAGLE simulations. We identify the present-day green valley galaxies using entropic thresholding and track the evolution of the physical properties of their progenitors up to $z=10$. Our study identifies three distinct phases in their evolution: (i) an early growth phase ($z=10-6$), where progenitors are gas-rich, efficiently form stars, and experience AGN feedback regulating star formation in massive galaxies, (ii) a transition phase ($z=6-2$), marked by frequent interactions and mergers in higher-density environments, driving starbursts, depleting gas reservoirs, and strengthening correlations between cold gas and halo properties, and (iii) a quenching phase ($z=2-0$), dominated by environmental and mass-dependent processes that suppress star formation and deplete cold gas. Our analysis shows that at $z<1$, environmental factors and cold gas depletion dominate quenching, with tighter correlations between stellar mass, SFR, and cold gas content. The interplay between mass and environmental density during this period drives diverse and distinct evolutionary pathways. Our analysis shows that majority of the main progenitor branches of the present-day GV galaxies entered the green valley at $z<1$. We also find that a small fraction ($\sim 5\%$) of the main progenitor branches had already crossed the green valley and joined the red sequence by $z=0.1$, indicating that some galaxies may undergo late-time rejuvenation, that allows them to reenter the green valley by the present day. Our findings provide a comprehensive view of the mechanisms shaping the GV population across cosmic time.