photoz_bias¶
Modify a set of loaded n(z) distributions with a multiplicative or additive bias
File |
number_density/photoz_bias/photoz_bias.py |
Attribution |
CosmoSIS Team |
URL |
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))
Assumptions¶
Simple photo-z bias models: n(z) -> n(z-b) or n(z*(1-b))
Setup Parameters¶
Name |
Type |
Default |
Description |
|---|---|---|---|
mode |
str |
‘multiplicative’ or ‘additive’, depending on what kind of bias model you want |
|
sample |
str |
If set, look for n(z) in the section called sample, and error parameters in sample_errors |
|
bias_section |
str |
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 |
str |
cubic |
Type of interpolation to use in scipy.interpolate.interp1d |
per_bin |
bool |
True |
Whether to use one value per bin, If False, use one value for all bins. |
output_deltaz_section_name |
string |
If set, compute the mean of the shifted n(z) and writes it to the specified section. |
Input values¶
Section |
Name |
Type |
Default |
Description |
|---|---|---|---|---|
wl_number_density |
nbin |
int |
Number of redshift bins |
|
z |
real 1d |
Redshift sample points of n(z) estimates |
||
bin_i |
real 1d |
n(z)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 delta-z for this bin. |
Output values¶
Section |
Name |
Type |
Description |
|---|---|---|---|
wl_number_density |
bin_i |
real 1d |
n(z) for i=1..nbin. Modified n(z) estimates replaced old value |
delta_z_out |
bin_i |
real 1d |
mean of the new n(z) for i=1..nbin. |