Age and Metallicity of galaxies in different environments of the Coma supercluster

Abstract

We analyse luminosity-weighted ages and metallicity (Z ) of galaxies in a continuous range of environments, i.e. clusters, filaments and voids prevalent in the Coma supercluster (∼ 100ℎ −1 Mpc). Specifically, we employ two absorption line indices, H and ⟨Fe⟩ as tracers of age and metallicity of galaxies. We find that the stellar-phase metallicity of galaxies declines with increasing age as a function of stellar mass ( * ) as well as environment. On the filaments, metallicity of galaxies varies as a function of their distance from the spine of the filament, such that galaxies closer to the centre of the filaments have lower metallicity relative to their counterparts 1 Mpc away from it. The mean age of intermediate mass galaxies (10 10 < * ∕ ⊙ < 10 10.5 ) galaxies is statistically significantly different in different environments such that, the galaxies in clusters are older than the filament galaxies by 1-1.5 Gyr, while their counterparts in the voids are younger than filament galaxies by ∼ 1 Gyr. The massive galaxies ( * ∕ ⊙ > 10 10.5 ), on the other hand show no such difference for the galaxies in clusters and filaments, but their counterparts in voids are found to be younger by ∼ 0.5 Gyr. At fixed age however, Z of galaxies is independent of their * in all environments, except the most massive ( * ∕ ⊙ ≳ 10 10.7 ), oldest galaxies (≳ 9 Gyr) which show a sharp decline in their Z with * . Our results support a scenario where galaxies in the nearby Universe have grown by accreting smaller galaxies or primordial gas from the large-scale cosmic web.

Study of galaxies on large-scale filaments in simulations

“…The respective probability for Z NSF for group galaxies is found to be 0. Such trends of lower Z in the most massive galaxies have also been observed in the Coma cluster (Poggianti et al 2001), and the Coma supercluster (Tiwari et al 2020). slope of the mass-metallicity relation is primarily determined by the galaxies in dense environments.…”