Accurate Determination of the Free–Free Gaunt Factor – II. Relativistic Gaunt Factors

Authors

P. A. M. van Hoof, Royal Observatory of Belgium, Belgium
Gary J. Ferland, University of KentuckyFollow
R. J. R. Williams, AWE plc, UK
K. Volk, Space Telescope Science Institute
Marios Chatzikos, University of KentuckyFollow
M. Lykins, University of Kentucky
R. L. Porter, University of Georgia

Abstract

When modelling an ionized plasma, all spectral synthesis codes need the thermally averaged free–free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum. Until now no data set exists that would meet these needs completely. We have therefore produced a table of relativistic Gaunt factors over a much wider range of parameter space than has ever been produced before. We present tables of the thermally averaged Gaunt factor covering the range ¹⁰log γ² = −6 to 10 and ¹⁰log u = −16 to 13 for all atomic numbers Z = 1 through 36. The data were calculated using the relativistic Bethe–Heitler–Elwert (BHE) approximation and were subsequently merged with accurate non-relativistic results in those parts of the parameter space where the BHE approximation is not valid. These data will be incorporated in the next major release of the spectral synthesis code CLOUDY. We also produced tables of the frequency integrated Gaunt factor covering the parameter space ¹⁰log γ² = −6 to +10 for all values of Z between 1 and 36. All the data presented in this paper are available online.

Document Type

Article

Publication Date

5-11-2015

Notes/Citation Information

Published in Monthly Notices of the Royal Astronomical Society, v. 449, no. 2, p. 2112-2118.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1093/mnras/stv404

Funding Information

PAMvH acknowledges support from the Belgian Science Policy Office through the ESA PRODEX program. GJF acknowledges support by NSF (1108928, 1109061, and 1412155), NASA (10-ATP10-0053, 10-ADAP10-0073, NNX12AH73G, and ATP13-0153), and STScI (HST-AR-13245, GO-12560, HST-GO-12309, and GO-13310.002-A).

Repository Citation

van Hoof, P. A. M.; Ferland, Gary J.; Williams, R. J. R.; Volk, K.; Chatzikos, Marios; Lykins, M.; and Porter, R. L., "Accurate Determination of the Free–Free Gaunt Factor – II. Relativistic Gaunt Factors" (2015). Physics and Astronomy Faculty Publications. 272.
https://uknowledge.uky.edu/physastron_facpub/272