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clerkin module
Compute galaxy bias as function of k, z for 3-parameter Clerkin et al 2014 model
Name: clerkin
File: cosmosis-standard-library/bias/clerkin/clerkin_interface.py
Version: 1
Author(s):
- L. Clerkin
URL:
Cite:
- arXiv:1405.5521
- Cole et al, MNRAS, 362, 2, 505–534
Rules:
- Please cite the relevant papers if you use this module.
Assumptions:
- 3-parameter bias model from Clerkin et al l 2014
Explanation
The GTD bias model provides a benchmark expression for
the redshift evolution of galaxy bias on large scales.
This is crucial for rigorous comparison or combination
of results. Choice of biasing model has a significant
impact on cosmological parameter constraints, and an
incorrect bias model will cause a shift in measured
values of cosmological parameters. The three parameter
GTD model, which encompasses several common bias models,
has been shown to outperform the popular approach of a
binned constant bias in obtaining unbiased estimates of
cosmological parameters.
The GTD model is:
b(z) = c + (b_0 - c) / D(z)^alpha
where D(z) is the growth factor.
The Q model is:
b(k) = (1+Q k^2) / (a+A k)
This module creates bias fields and/or scales power spectra,
depending on the chosen options
The version of this model without redshift dependence is from Cole et al.
##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 |
|---|---|
| bias_only | (bool, default=F) If set, do not use the matter power spectrum, just save the bias field |
| model | 'gtd', 'q', or 'q-gtd' to use the GTD three-parameter model (z evolution only), the 2-parameter Q model (k scale only) or both |
| suffix | (string, default='') A suffix to append to the output section names below |
##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 |
|---|---|---|
| galaxy_bias | b0 | real scalar. bias at z=0 if GTD model used |
| c | real scalar. bias parameter for GTD model | |
| alpha | real scalar. power law index for growth in GTD model | |
| Q | real scalar. parameter of Q model | |
| A | real scalar. parameter of Q model | |
| matter_power_nl | k_h | 1D real vector, wavenumber in h/Mpc only if mode=power or both |
| z | 1D real vector, redshift only if mode=power or both | |
| P_k | 2D real vector, nonlinear matter power only if mode=power or both |
##Outputs
These parameters and data are computed as outputs from the module
| Section | Parameter | Description |
|---|---|---|
| galaxy_power | k_h | 1D real vector, wavenumber in h/Mpc, only if bias_only=F |
| z | 1D real vector, redshift, only if bias_only=F | |
| P_k | 2D real vector, galaxy power, only if bias_only=F | |
| matter_galaxy_power | k_h | 1D real vector, wavenumber in h/Mpc, only if bias_only=F |
| z | 1D real vector, redshift, only if bias_only=F | |
| P_k | 2D real vector, matter-galaxy cross power, only if bias_only=F | |
| bias_field | k_h | 1D real vector, wavenumber in h/Mpc |
| z | 1D real vector, redshift | |
| b | 2D real vector, galaxy bias | |
| r | 2D real vector, stochastic bias (identically 1 for these models) |
Updated