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README.ForGet
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README.ForGet
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ForGet
1 Introduction.
ForGet generates realizations of different galactic and extragalactic
foregrounds relevant to intensity mapping experiments. 4 types of
foregrounds are currently implemented:
a) Galactic synchrotron (polarized and unpolarized).
b) Galactic free-free (Bremsstrahlung emission).
c) Extra-galactic free-free.
d) Extra-galactic point sources.
The foregrounds b-d are simply generated as gaussian realizations of
the angular power-spectra C_l(nu1,nu2) modelled by Santos, Cooray
& Knox, 2005, with the parameters given in our companion paper.
On the other hand, galactic synchrotron is arguably the most relevant
foreground for intensity mapping. Not only does it have the largest
amplitude by far, but also its polarized part is not spectrally smooth
due to Faraday rotation within the galaxy, which is potentially harmful
in the context of foreground subtraction due to polarization leakage.
On top of this, since it is a galactic foreground, synchrotron emission
is not isotropic, being larger close to the galactic plane and dropping
towards high galactic latitudes. For these reason a slightly different
method was used to simulate this foreground, the details of which can
be found in arXiv:1405.1751.
In what follows we will briefly describe the compilation, usage, input
and output of ForGet.
2 Compilation and usage.
These instructions are the same for both ForGet and JoinT.
To compile ForGet and JoinT, open the Makefile and edit it according
to your system. The default compilation options should work for most
systems.
ForGet and JoinT use 3 external packages:
- CFITSIO. FITS format library.
- HEALPix. C library should be installed (version >=3.10).
- LIBSHARP. Spherical Harmonic Transform library.
The paths to the corresponding header files and libraries should be
correctly set in the Makefile.
Once the Makefile has been editted, typing 'make' should generate
the executables 'ForGet' and 'JoinT'. To run them just type
> ./<exec_name> <param_file>
where <exec_name> is either of the executables and <param_file> is the
path to their corresponding parameter file (see section 3).
3 Parameter file.
The behaviour of ForGet is mainly controlled by the input param file.
The param file is basically a set of name-value pairs. Any blank lines
and anything beyond a #-symbol will be ignored. We provide a sample
param file (param_ForGet_sample.ini) that includes all the input
parameters needed by ForGet. The comments included in this file
explain the meaning and functionality of these parameters.
4 Output.
The output of ForGet is a set of fits-files containing the HEALPix
maps corresponding to the foreground selected for the run in different
frequency bands. For instance, for the values used in param_ForGet_sample.ini,
the output maps would be stored in test_001.fits - test_150.fits. These
maps will be stored with RING ordering. If running with do_polarization= 1,
each output FITS file will contain the three Stokes parameters (I,Q,U).