Tracing the quenching history of cluster galaxies in the EAGLE simulation

Abstract

We use the EAGLE hydrodynamical simulation to trace the quenching history of galaxies in its 10 most massive clusters. We use two criteria to identify moments when galaxies suffer significant changes in their star formation activity: i) the instantaneous star formation rate (SFR) strongest drop, Γ SD SFR , and ii) a "quenching" criterion based on a minimum threshold for the specific SFR of 10 −11 yr −1 . We find that a large fraction of galaxies ( 60%) suffer their Γ SD SFR outside the cluster's R 200 . This "pre-processed" population is dominated by galaxies that are either low mass and centrals or inhabit low mass hosts (10 10.5 M M host 10 11.0 M ). The host mass distribution is bimodal, and galaxies that suffered their Γ SD SFR in massive hosts (10 13.5 M M host 10 14.0 M ) are mainly processed within the clusters. Pre-processing mainly limits the total stellar mass with which galaxies arrive in the clusters. Regarding quenching, galaxies preferentially reach this state in high-mass halos (10 13.5 M M host 10 14.5 M ). The small fraction of galaxies that reach the cluster already quenched has also been preprocessed, linking both criteria as different stages in the quenching process of those galaxies. For the z = 0 satellite populations, we find a sharp rise in the fraction of quenched satellites at the time of first infall, highlighting the role played by the dense cluster environment. Interestingly, the fraction of pre-quenched galaxies rises with final cluster mass. This is a direct consequence of the hierarchical cosmological model used in these simulations.

The GOGREEN survey: post-infall environmental quenching fails to predict the observed age difference between quiescent field and cluster galaxies at z > 1

“…So-called 'pre-processing' within galaxy group environments may be an important preceding process (e.g. Zabludoff & Mulchaey 1998;Fujita 2004;McGee et al 2009;De Lucia et al 2012;Pallero et al 2019). Observations at higher redshifts have the potential to remove some of the degeneracies associated with this empirical picture, in part because the evolution in galaxy properties like SFRs and gas fractions is decoupled from the rate of dark matter halo mass growth (e.g.…”

The GOGREEN survey: dependence of galaxy properties on halo mass at z > 1 and implications for environmental quenching

“…A simple objective definition of this accretion time is the moment when a galaxy crosses R 200 1 for the first time (Balogh, Navarro & Morris 2000). However, simulations suggest environment first becomes important when satellites are cut off from cosmological accretion, which can happen well outside R 200 (Behroozi et al 2014;Bahé & McCarthy 2015;Pallero et al 2019).…”

“…Alternatively, the physically relevant definition could be the first time a galaxy is accreted on to any more massive halo and hence first becomes a satellite. The latter is often referred to as 'pre-processing'; observations and simulations both indicate that 'pre-processing' may be important for a significant proportion of galaxies and that at least some cluster galaxies had their star formation quenched in M halo ≥ 10 13 M groups prior to being accreted into massive clusters (Zabludoff & Mulchaey 1998;Kawata & Mulchaey 2008;Berrier et al 2009;McGee et al 2009;De Lucia et al 2012;Hou et al 2014;Pallero et al 2019;Donnari et al 2021).…”

The Roles of Mass and Environment in the Quenching of Galaxies. II.

“…During the last decades, the scientific community has spent a considerable amount of effort and resources with the purpose of learning more about the physical processes that drive galaxy formation and evolution and, among them, those responsible for the quenching of the star formation activity in galaxies, which is fundamentally important. Galaxy quenching is, indeed, thought to have a remarkable role in shaping galaxy properties, such as morphology, colors and stellar age (Blanton et al 2003;Baldry et al 2004;Kauffmann et al 2004;Brinchmann et al 2004;Balogh et al 2004;Cassata et al 2008;Muzzin et al 2012Muzzin et al , 2013Pallero et al 2019;Davies et al 2019, and others).…”