Some Ionization and Recombination Data Needs for Cosmic Atomic Plasmas

Abstract

Cosmic atomic plasmas can be divided into two broad classes: electron ionized and photoionized. Electron‐ionized plasmas are formed in objects such as the sun and other stars, supernova remnants, galaxies, and the intercluster medium in clusters of galaxies. Photoionized plasmas are formed in objects such as planetary nebulae, H II regions, X‐ray binaries, and active galactic nuclei. Understanding the spectral and thermal properties of these objects requires an accurate knowledge of the ionization level of the gas. This in turn depends on a reliable understanding of the underlying ionization and recombination processes which determine the ionization balance. Here we review some of the various atomic collision processes which determine the charge state distribution in a cosmic atomic plasma and briefly discuss some of the recent theoretical and experimental advances in generating the needed atomic data. We close by describing the relevant atomic data needs for the near future.