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photoz_bias module
Modify a set of loaded n(z) distributions with a multiplicative or additive bias
Name: photoz_bias
File: cosmosis-standard-library/number_density/photoz_bias/photoz_bias.py
Version: 1
Author(s):
- CosmoSIS Team
URL:
Cite:
Rules:
Assumptions:
- Simple photo-z bias models: n(z) -> n(z-b) or n(z*(1-b))
Explanation
Photometric redshift distributions can contain biases - the actual distribution
of galaxies in a survey can be different to the estimated one.
This bias can remain even after calibration with a spectroscopic sample, or by other methods.
This module models the simplest possible type of n(z) bias - a simple shift in z by a multiplicative
or additive factor. The idea is that the shift parameter should be marginalized in sampling over to
account for this bias. Note that this is not the same as simply widening the n(z).
Ranges or priors should be put on the size of the bias that reflect your knowledge of remaining
possible biases.
The mode is:
n(z) -> n(z-b) or n(z*(1-b))
##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 |
|---|---|
| mode | String; 'multiplicative' or 'additive', depending on what kind of bias model you want |
| sample | String, optional; If set, look for n(z) in the section called sample, and error parameters in sample_errors |
| bias_section | String, optional; If set, look for input parameters in this named section instead of wl_photoz_errors. If not set but sample is set, look in sample_errors |
| interpolation | String, default=cubic. Type of interpolation to use in scipy.interpolate.interp1d |
| per_bin | Bool, default=T. Use one value per bin, if False, one value for all bins |
##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 |
|---|---|---|
| wl_number_density | nbin | Integer; number of redshift bins |
| z | Real vector; redshift sample points of n(z) estimates | |
| bin_i | Real vectors; for i=1..nbin. n(z) estimates | |
| wl_photoz_errors | bias_i | Real; for i=1..nbin if per_bin=T or i=0 otherwise. Bias size for this bin. |
##Outputs
These parameters and data are computed as outputs from the module
| Section | Parameter | Description |
|---|---|---|
| wl_number_density | bin_i | Real vectors; for i=1..nbin. Modified n(z) estimates replaced old value |
Updated