Chemical pre-processing of cluster galaxies over the past 10 billion years in the IllustrisTNG simulations

Abstract

We use the IllustrisTNG simulations to investigate the evolution of the mass-metallicity relation (MZR) for star-forming cluster galaxies as a function of the formation history of their cluster host. The simulations predict an enhancement in the gas-phase metallicities of starforming cluster galaxies (10 9 < M * < 10 10 M ⊙ /h) at z ≤ 1.0 in comparisons to field galaxies. This is qualitatively consistent with observations. We find that the metallicity enhancement of cluster galaxies appears prior to their infall into the central cluster potential, indicating for the first time a systematic "chemical pre-processing" signature for infalling cluster galaxies. Namely, galaxies which will fall into a cluster by z = 0 show a ∼ 0.05 dex enhancement in the MZR compared to field galaxies at z ≤ 0.5. Based on the inflow rate of gas into cluster galaxies and its metallicity, we identify that the accretion of pre-enriched gas is the key driver of the chemical evolution of such galaxies, particularly in the stellar mass range (10 9 < M * < 10 10 M ⊙ /h). We see signatures of an environmental dependence of the ambient/inflowing gas metallicity which extends well outside the nominal virial radius of clusters. Our results motivate future observations looking for pre-enrichment signatures in dense environments.

Baryons in the Cosmic Web of IllustrisTNG – I: gas in knots, filaments, sheets, and voids

“…In general, wherever this phase exists, it is already metal enriched at high redshift. This result is in agreement with the completely independent analysis of Illus-trisTNG performed by Gupta et al (2018) and with work by other authors (e.g. Martizzi et al 2016;Biffi et al 2017Biffi et al , 2018, who also found evidence for early metal enrichment in the progenitors of galaxy cluster galaxies at high redshift.…”

SDSS-IV MaNGA: Evidence for Enriched Accretion onto Satellite Galaxies in Dense Environments

“…In this picture, which has been motivated by both observations (Peng & Maiolino 2014) and simulations (Oppenheimer et al 2010;Anglés-Alcázar et al 2017;Gupta et al 2018), feedback-driven winds expel metal-rich gas from a massive star-forming central that is subsequently accreted onto nearby satellites. While our estimates for the metallicity of gas accreted onto satellite galaxies are a factor of ∼3 lower than the predictions of Gupta et al (2018), we note that the values returned by our modeling are subject to inherent uncertainties in the nucleosynthetic yield, the gas return fraction from stellar evolution, and the absolute abundance scaling of the strong-line metallicity diagnostics. Notwithstanding these systematic effects, the inferred differential in the metallicity of gas accreted onto satellites in different environments is qualitatively in good agreement with the simulations.…”

“…Numerical simulations of galaxy evolution are beginning to show that the gas being accreted onto galaxies cannot be assumed to be pristine in all environments (Oppenheimer et al 2010;Gupta et al 2018). In the simulations, the origin of accreted gas is observed to be highly dependent on redshift, with cosmological accretion of low-metallicity gas dominating at high redshift.…”

“…In the FIRE simulations, Anglés-Alcázar et al (2017) found that the exchange of gas between galaxies that is facilitated by galactic winds dominates the accretion budget by z=0. Gupta et al (2018) explored this effect using data from the IllustrisTNG simulations. They showed that the enrichment of the intergalactic medium and the associated accretion onto galaxies is dependent on both the halo mass and whether a galaxy is infalling into its host halo or has been a satellite for some time.…”

“…Historically, it was often assumed that the gas fueling star formation is accreted in a chemically pristine state (e.g., Larson 1972;Quirk & Tinsley 1973;Finlator & Davé 2008;Mannucci et al 2010). However, there is mounting evidence that this is not the case (Oppenheimer et al 2010;Rubin et al 2012;Brook et al 2014;Kacprzak et al 2016;Gupta et al 2018). While work such as that done by Peng & Maiolino (2014) relies on the inference of the properties of gas in the intergalactic medium from modeling, there is a growing body of observations that are able to directly probe the metallicity of gas outside of galaxies by measuring the absorption of background quasar light by extragalactic clouds (Lehner et al 2013;Prochaska et al 2017).…”