RECFAST
A code to calculate the recombination history of the
Universe
This code is meant to reproduce the calculations described in the paper
"A new calculation of the recombination epoch",
Seager, S., Sasselov, D. & Scott, D., 1999, ApJ, 523, L1
(astro-ph/9909275),
which is a fast
approximation to the detailed calculations described in
"How exactly did the Universe become neutral?"
Seager, S., Sasselov, D. & Scott, D., 2000, ApJS, 128, 407
(astro-ph/9912182).
And with some updates (to He etc.) which are described in
Wong, W.Y., Moss, A. & Scott, D., 2008, MNRAS, 386, 1023
(arXiv:0711.1357),
together with the Compton coupling treatment in
Scott, D. & Moss A., 2009, MNRAS, submitted
(arXiv:0902.3438),
Here are things that the code treats:
- Solves H and He simultaneously
- Kinetic temperature of matter evolved separately, including Compton
and adiabatic cooling
- Careful consideration of dependency of quantities on TM and
TR
- Accurate values of all relevant physical constants
- Full treatment of background cosmology, including radiation, Lambda
and curvature (but no explicit "w")
- Saha assumed for ionized helium
- Accurate look-up table for recombination coefficients
- Approximation for H recombination at low redshift, to account for
out of equilibrium
- Singlet and triplet states considered for neutral He
- Additional "fudge factor" for He recombination
- Solves for temperature difference between matter and radiation,
giving smoother transition in Tmat evolution
This results in xe(z) producing (probably) sub-percent
accuracy for CMB anisotropy Cls
There are 2 separate versions of the code, one in fortran (developed by
DS), and one in C (developed by SS).
RECFAST.FOR
Current version 1.4.2 (September 2008)
You can get recfast.for
and recfast.readme here.
You can also still get
version1.4.1 (August 2008),
as well as version1.3 (October 2006),
version1.2 (June 2003)
and version1.0 (October 2001).
A bug has been fixed that caused overflow on some types of computer (Feb 2000).
Other minor bugs have also been noted and fixed. Some problems with
Helium recombination were also pointed out and corrected (June 2003).
Version 1.3 includes 3 minor corrections (value of G, m_He/m_H ratio and an
error of x for x_H in f(1)).
Version 1.4 includes modifications to account for the effects of Helium,
especially the new fudge factor. "Heswitch" should be set to 6 to include
all the new effects.
RECFAST.C
Note: this code is not currently up-to-date with bug fixes etc.
The C code, with makefile etc. is available
here
and here.
The current version of the code links to Numerical Recipes (NR), which is
copyright - hence users will require their own NR library. Details of
the modifications to NR routines and how to link are fully explained at
these urls.
Please e-mail any comments to
dscott@astro.ubc.ca
or seager@dtm.ciw.edu
Douglas Scott
dscott@astro.ubc.ca
Last revised: 11th September 2008