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cl_to_xi_nicaea module
Compute WL correlation functions xi+, xi- from C_ell
Name: cl_to_xi_nicaea
File: cosmosis-standard-library/shear/cl_to_xi_nicaea/nicaea_interface.so
Version: 1.0
Author(s):
- Martin Kilbinger
- Nicaea Team
URL:
Cite:
Rules:
Assumptions:
- Input C_ell sufficiently well-sampled over standard pre-defined range
Explanation
The correlation functions are related to the spectra via Bessel functions:
xi_{(+/-)}(theta) = \int_0^\infty C_\ell J_{(0,4)}(\ell \theta) \ell d\ell / 2\pi
In this module that integral is done via a Hankel Transform.
This module is a part of the Nicaea code, with the interface written by Niall
Maccrann. It avoids the ringing problems of the alternative cl_to_xi code but
generates results only on a fixed range in theta .
The output theta values will always be from about 2.0e-07 to 1.0e+04 radians, but
only in part of that regime, from about 1 to a few hundred arcmin, will the results
be numerically valid. The input ell must include the corresponding range, and
will be extrapolated linearlly before that and cubically after it.
##Parameters
These parameters can be set in the module's section in the ini parameter file.
If no default is specified then the parameter is required.
| Parameter | Description |
|---|---|
| corr_type | Integer, either 0 (to do shear EE C_ell -> xi+(theta) and xi-(theta)), or 1 (to convert galaxy position C_ell to w(theta)) or 2 (to convert the cross galaxy position-shear C_ell to gamma_t(theta)) |
| input_section_name | String, name of the angular power spectrum input section. See shear/spectra module. (Default: 'shear_cl', 'galaxy_cl', or 'galaxy_shear_cl' depending on corr_type) |
| output_section_name | String, name of the angular correlation function output section (Default: 'shear_xi', 'galaxy_shear_xi', or 'galaxy_xi' depending on corr_type) |
##Inputs
These parameters and data are inputs to the module, either supplied as parameters by the sampler or computed by some previous module. They are loaded from the data block.
| Section | Parameter | Description |
|---|---|---|
| input_section_name | ell | Real 1d array, sample ell values for input C_ell |
| nbin_a | Integer, mainly for mode=2 (GGL) - the number of redshift bins in the first quantity (position bins for GGL) | |
| nbin_b | Integer, mainly for mode=2 (GGL) - the number of redshift bins in the first quantity (shear bins for GGL) | |
| nbin | Integer, Number of redshift bins used if nbin_a or b not found. | |
| bin_i_j | Real 1d arrays C_ell (no l(l+1) factor) for bin i and j. Only need j<=i for modes 0 and 1. |
##Outputs
These parameters and data are computed as outputs from the module
| Section | Parameter | Description |
|---|---|---|
| output_section_name | theta | Real 1D array, Sample theta values for output xi(theta) |
| xiplus_i_j | Real 1D arrays, xi_plus(theta) bin i and j, only if mode=0 Only stores j<=i. | |
| ximinus_i_j | Real 1D arrays, xi_minus(theta) bin i and j, only if mode=0. Only stores j<=i. | |
| bin_i_j | Real 1D array, w(theta) or gamma_t(theta) for bin i and j, only if mode=1 or 2 respectively. Only stores j<=i. | |
| nbin_a | Integer, number of i tomographic bins | |
| nbin_b | Integer, number of j tomographic bins |
Updated