Green’s function method
Green’s function method
Computations of the CMB spectral distortion caused by different energy-release mechanisms using the full thermalization code ‘CosmoTherm’ is rather time-consuming. ‘CosmoTherm’ is thus not well-suited for parameter estimation and experimental forecasts. However, since from COBE/FIRAS we know that distortions have to be small, the problem can be linearized. In this case, a Green’s function approach can be used to approximate the distortion created by energy release in an efficient and quasi-exact way. The Green’s function for different heating redshifts is illustrated in Fig. 1 (adapted from Chluba, 2013, MNRAS, 434, 352).
Fig. 1: Change in the CMB spectrum after single energy release at different heating redshifts, zh. At z > few x 106, a temperature shift is created. At z ~ 3 x 105 a pure µ-distortion appears, while at z < 104 a pure y-distortion is created. At all intermediate stages, the signal is given by a superposition of these extreme cases with some residual that contains information about the time-dependence of the energy-release process.
•Chluba & Sunyaev, 2012, MNRAS, 419, 1294 (arXiv:1109.6552)
•Chluba, 2013, MNRAS, 434, 352 (arXiv:1304.6120)
The routines with different examples are available in the package ‘Greens’, which can be downloaded here. The current version is Greens v1.0.2 (Oct. 2013), and the tar-file is about 5MB large (mainly because of the precomputed Green’s function database). The package also includes Python binding and a simple Monte-Carlo toolkit that allows forecasts for different energy-release scenarios.
When using the ‘Greens’ package please consider referring to:
For comments, questions, or bug reports please email: Jens@Chluba.de.
Lastest Updates
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changed initialization sequence for Greens function
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added particle production case
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added user-defined P(k) setups
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fixed bug reports (thanks to Marius Millea)
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added some header information to main output functions
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added some options to 'plot_joint_dist.py'
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added runmodes and setup for step and bend power spectrum cases
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initial version of Green's function routines
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executable is created to run these modes with different settings
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different examples are given in 'run_Greens.cpp'
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python part hosted in './python/'