Time-dependent Cooling in Photoionized Plasma

Orly Gnat*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


I explore the thermal evolution and ionization states in gas cooling from an initially hot state in the presence of external photoionizing radiation. I compute the equilibrium and nonequilibrium cooling efficiencies, heating rates, and ion fractions for low-density gas cooling while exposed to the ionizing metagalactic background radiation at various redshifts (z = 0 - 3), for a range of temperatures (108-104 K), densities (10-7-103cm-3), and metallicities (10-3-2 times solar). The results indicate the existence of a threshold ionization parameter, above which the cooling efficiencies are very close to those in photoionization equilibrium (so that departures from equilibrium may be neglected), and below which the cooling efficiencies resemble those in collisional time-dependent gas cooling with no external radiation (and are thus independent of density).

Original languageAmerican English
Article number11
JournalAstrophysical Journal, Supplement Series
Issue number2
StatePublished - Feb 2017

Bibliographical note

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved..


  • ISM: general
  • atomic processes
  • intergalactic Medium
  • plasmas
  • quasars: absorption lines


Dive into the research topics of 'Time-dependent Cooling in Photoionized Plasma'. Together they form a unique fingerprint.

Cite this