The large-scale distribution of ionized metals in IllustrisTNG

Abstract

ABSTRACT We study the intrinsic large-scale distribution and evolution of seven ionized metals in the IllustrisTNG magnetohydrodynamical cosmological simulation. We focus on the fractions of C ii, C iv, Mg ii, N v, Ne viii, O vi, and Si iv in different cosmic web structures (filaments, haloes, and voids) and gas phases (warm–hot intergalactic medium, hot, diffuse, and condensed gas) from z = 6 to z = 0. Our analysis provides a new perspective to the study of the distribution and evolution of baryons across cosmic time while offering new hints in the context of the well-known missing baryons problem. The cosmic web components are here identified using the local comoving dark matter density, which provides a simple but effective way of mapping baryons on large scales. Our results show that C ii and Mg ii are mostly located in condensed gas inside haloes in high-density and low-temperature star-forming regions ($\rho _{\rm gas}/\bar{\rho }_{\rm bar}\gtrsim 10^3$, and T ≲ 105 K). C iv and Si iv present similar evolution of their mass fractions in haloes and filaments across cosmic time. In particular, their mass budgets in haloes in condensed phase ($\rho _{\rm gas}/\bar{\rho }_{\rm bar}\gtrsim 10^3$, and T ≲ 105 K) are driven by gas cooling and star formation with a peak at z ∼ 2. Finally, our results confirm that O vi, Ne viii, and N v are good tracers of warm/hot and low-density gas at low redshift ($\rho _{\rm gas}/\bar{\rho }_{\rm bar}\lesssim 10^3$, and T ≳ 105 K), regions that are likely to contain most of the missing baryons in the local Universe.