Low-temperature opacities

Jason W. Ferguson, David R. Alexander, France Allard, Travis Barman, Julia G. Bodnarik, Peter H. Hauschildt, Amanda Heffner-Wong, Akemi Tamanai

Research output: Contribution to journalArticlepeer-review

949 Scopus citations


Previous computations of low-temperature Rosseland and Planck mean opacities from Alexander & Ferguson are updated and expanded. The new computations include a more complete equation of state (EOS) with more grain species and updated optical constants. Grains are now explicitly included in thermal equilibrium in the EOS calculation, which allows for a much wider range of grain compositions to be accurately included than was previously the case. The inclusion of high-temperature condensates such as Al2O 3 and CaTiO3 significantly affects the total opacity over a narrow range of temperatures before the appearance of the first silicate grains. The new opacity tables are tabulated for temperatures ranging from 30,000 to 500 K with gas densities from 10-4 to 10-19 g cm-3. Comparisons with previous Rosseland mean opacity calculations are discussed. At high temperatures, the agreement with OPAL and Opacity Project is quite good. Comparisons at lower temperatures are more divergent as a result of differences in molecular and grain physics included in different calculations. The computation of Planck mean opacities performed with the opacity sampling method is shown to require a very large number of opacity sampling wavelength points; previously published results obtained with fewer wavelength points are shown to be significantly in error. Methods for requesting or obtaining the new tables are provided.

Original languageEnglish (US)
Pages (from-to)585-596
Number of pages12
JournalAstrophysical Journal
Issue number1 I
StatePublished - Apr 10 2005


  • Atomic data
  • Equation of state
  • Methods: numerical
  • Molecular data

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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