paper

The roles of environment and interactions on the evolution of red and blue galaxies in the EAGLE simulation

arXiv:2402.05788 · doi:10.1088/1475-7516/2024/08/060

Abstract

We study the evolution of the red and blue galaxies from to using the EAGLE simulation. The galaxies in the blue cloud and the red sequence are separated at each redshift using a scheme based on Otsu's method. Our analysis shows that the two populations have small differences in the local density and the clustering strength until , after which the red galaxies preferentially occupy the denser regions and exhibit a significantly stronger clustering than the blue galaxies. The significant disparities in cold gas mass and specific star formation rate (sSFR) observed before suggest that factors beyond environmental influences may also contribute to the observed dichotomy. Interacting galaxy pairs at a given separation exhibit a higher SFR at increasing redshifts, which may be linked to the rising gas fractions at higher redshift. As redshift decreases, the SFR decreases across all separations, suggesting a gradual depletion of the cold gas reservoir. At pair separations kpc, an anomalous increase in the SFR among paired galaxies in isolation around suggests that environmental effects begin to dominate at this redshift, thereby increasing the rate of galaxy interactions and the occurrence of starburst galaxies. We observe a substantial decrease in the blue fraction in paired galaxies starting from to the present. However, the decrease in the blue fraction in paired galaxies with their second nearest neighbour at a distance greater than 500 kpc continues until , after which the blue fraction begins to increase.

22 pages, 10 figures, significantly revised, Accepted for publication in JCAP

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