Ion densities of cold clouds driven by galactic outflows

TL;DR

This study uses cloud-crushing simulations to explore ion distributions in cold clouds within the hot circumgalactic medium, revealing complex multiphase features but failing to reproduce high ions like O VI observed in quasar absorption systems.

Contribution

It introduces detailed simulations of cold clouds in the CGM to analyze ion distributions and their spectral signatures, advancing understanding of multiphase interactions.

Findings

Ions with different ionization potentials can coexist in the same absorber.

Simulations reproduce some multiphase features but not high ions like O VI.

High ions remain unexplained by the current models.

Abstract

Observations of the circumgalactic medium (CGM) often display coincident absorption from species with widely varying ionization states, providing direct evidence for complex, multiphase interactions. Motivated by these measurements, we perform a series of cloud-crushing simulations that model cold clouds traveling through the hot CGM. We analyze the ion distributions of these clouds, generate mock absorption spectra, and study their implications on quasar (QSO) absorption observations. Our results show interesting multiphase features, in which ions with significantly different ionization potentials exist in the same absorber and share similar spectral features. However, our simulations are unable to explain high ions like O \textsc{vi} and their coexistence with lower ions that appear in many observed QSO absorption systems.