Ion-by-ion cooling efficiencies

Orly Gnat, Gary J. Ferland

Research output: Contribution to journalArticlepeer-review

82 Scopus citations


We present ion-by-ion cooling efficiencies for low-density gas. We use Cloudy (version 10.00) to estimate the cooling efficiencies for each ion of the first 30 elements (H-Zn) individually. We present results for gas temperatures between 10 4 and 10 8 K, assuming low densities and optically thin conditions. When nonequilibrium ionization plays a significant role the ionization states deviate from those that obtain in collisional ionization equilibrium (CIE), and the local cooling efficiency at any given temperature depends on specific nonequilibrium ion fractions. The results presented here allow for an efficient estimate of the total cooling efficiency for any ionic composition. We also list the elemental cooling efficiencies assuming CIE conditions. These can be used to construct CIE cooling efficiencies for non-solar abundance ratios or to estimate the cooling due to elements not included in any nonequilibrium computation. All the computational results are listed in convenient online tables.

Original languageEnglish
Article number20
JournalAstrophysical Journal, Supplement Series
Issue number1
StatePublished - Mar 2012


  • ISM: general
  • atomic processes
  • plasmas

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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