Cloudy and the High-Resolution Microcalorimeter Revolution: Optical, UV, and X-ray Spectra of One-electron Systems

TL;DR

This paper enhances the Cloudy plasma code to resolve fine-structure energy levels, enabling it to produce high-resolution X-ray spectra that match upcoming XRISM microcalorimeter observations, improving diagnostics of hot astrophysical plasmas.

Contribution

The authors expand Cloudy to resolve fine-structure energy levels, allowing for accurate modeling of high-resolution X-ray spectra from microcalorimeter data.

Findings

Resolved Lyman lines as column density indicators.

Demonstrated sensitivity of lines to radiation fields and turbulence.

Produced spectra matching XRISM's spectral resolution.

Abstract

With the launch of the XRISM microcalorimeter mission, space-based X-ray observations will achieve a record spectral resolving power of $R\equiv E/\Delta E\sim$1200. With this resolving power, emission features associated with fine-structure energy levels of some species will be resolved, sometimes for the first time. The plasma code, Cloudy, was not originally designed for high-resolution X-ray spectroscopy and throughout its history did not resolve fine-structure components of Lyman lines. Here we expand Cloudy to resolve these fine-structure energy levels and obtain predicted X-ray spectra that match the resolution of new microcalorimeter observations. We show how the Lyman lines can be used as column density indicators in the hot X-ray emitting gas in a cluster of galaxies such as Perseus, and examine their sensitivity to external radiation fields and turbulence.