Cosmic distribution of highly ionized metals and their physical conditions in the EAGLE simulations

TL;DR

This study uses the EAGLE simulations to analyze the distribution, physical conditions, and evolution of highly ionized intergalactic metals, comparing predictions with observations from redshift 0 to 6.

Contribution

It provides a detailed analysis of metal ion distributions and their physical states in cosmological simulations, highlighting the effects of stellar feedback on metal properties and distribution.

Findings

Column density and metallicity increase with time and column density.

Collisionally ionized metal fraction grows with time and ionization energy.

Stellar feedback efficiency significantly impacts metal distribution and temperatures.

Abstract

We study the distribution and evolution of highly ionised intergalactic metals in the Evolution and Assembly of Galaxies and their Environment (EAGLE) cosmological, hydrodynamical simulations. EAGLE has been shown to reproduce a wide range of galaxy properties while its subgrid feedback was calibrated without considering gas properties. We compare the predictions for the column density distribution functions (CDDFs) and cosmic densities of SiIV, CIV, NV, OVI and NeVIII absorbers with observations at redshift z = 0 to ~ 6 and find reasonable agreement, although there are some differences. We show that the typical physical densities of the absorbing gas increase with column density and redshift, but decrease with the ionization energy of the absorbing ion. The typical metallicity increases with both column density and time. The fraction of collisionally ionized metal absorbers increases with time and ionization energy. While our results show little sensitivity to the presence or absence of AGN feedback, increasing/decreasing the efficiency of stellar feedback by a factor of two substantially decreases/increases the CDDFs and the cosmic densities of the metal ions. We show that the impact of the efficiency of stellar feedback on the CDDFs and cosmic densities is largely due to its effect on the metal production rate. However, the temperatures of the metal absorbers, particularly those of strong OVI, are directly sensitive to the strength of the feedback.