1997/11/14 by A. D. Challinor, A. N. Lasenby · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/305623
14 pages, 4 postscript figures. Uses epsfig. To appear in The Astrophysical Journal
arxiv created 1997/11/14 · arxiv updated 2009/12/01
We present an extension of the Kompaneets equation which allows relativistic effects to be included to any desired order. Using this, we are able to obtain simple analytic forms for the spectral changes due to the Sunyaev-Zel'dovich effect in hot clusters, correct to first and second order in the expansion parameter thetae=kB Te/m c2. These analytic forms agree with previous numerical calculations of the effect based upon the multiple scattering spectrum for kB Te up to 10 keV. Our results confirm previous conclusions that the result of including relativistic corrections in the Sunyaev-Zel'dovich effect is a small reduction in the amplitude of the effect over the majority of the spectrum: specifically we find Delta T/T = -2y(1 - 17/10 thetae + 123/40 thetae2) (correct to second-order) in the Rayleigh-Jeans region, where y is the usual Comptonization parameter. For a typical cluster temperature of 8 keV, this amounts to a correction downwards to the value of the Hubble constant derived using combined X-ray and Rayleigh-Jeans Sunyaev-Zel'dovich information by about 5 percent.