Overview of the modules¶
COLIBRÌ consists of simple Python files. One, named constants.py is just a collection of physical constants, useful numbers and conversion factors between different units of measurement. A second one, useful_functions.py contains some routines of everyday life for a cosmologist. The file fourier.py contains routines to perform Fourier and Hankel transforms. The remaining ones each contain one or more Python classes. Moreover two folders cotaining tests and Python notebooks are provided with the code.
In the following sections we briefly present the codes. The documentation for both classes and built-in methods is inside the code as well as on ReadTheDocs .
cosmology module¶
The main file of COLIBRÌ is without doubt the cosmology.py file.
This file contains one Python class, named colibri.cosmology.cosmo(), in whose initialization the cosmological parameters must be provided (otherwise the default values will be loaded).
This class has all the routines necessary to compute distances, ages, density parameters, halo mass functions, void size functions and power spectra.
For the latter, both Boltzmann solvers CAMB and Class can be used, provided their Python wrapper is correclty compiled (see Prerequisites), as well as the Eisenstein-Hu formula (see arXiv:9710252).
nonlinear module¶
Included here are several different ways to compute the non-linear matter power spectrum from a linear one.
These methods include HMcode2016 by Mead et al. (see arXiv:1505.07833 ), HMcode2020 by Mead et al. (see arXiv:2009.01858 ) Takahashi and Bird following the prescription by Takahashi et al. for the former (see arXiv:1208.2701 ) and the correction for the presence of massive neutrinos by Bird et al. for the latter (see arXiv:1109.4416 ).
limber module¶
The colibri.limber.limber() class inside this file is finalized to compute angular power spectra and correlation functions in the flat sky and Limber’s approximations. In this file are provided the routines to compute example functions for galaxy distributions (although different ones can be defined by the user outside the class) and window functions.
halo, galaxy, RSD¶
This three files are linked with each other. The basis is halo.py : it contains the class colibri.halo.halo() which computes the non-linear matter power spectrum according to the pure halo model (see for instance arXiv:0206508).
While this is known to return a poor description of the matter clustering, the class has routines able to compute properly halo mass functions and halo biases.
In the file galaxy.py the class colibri.galaxy.galaxy() is implemented, which uses the Halo Occupation Distribution (see e.g. arXiv:0408564) prescription to predict the galaxy power spectrum in real space.
Conversely, the redshift-space power spectrum is provided by the class colibri.RSD.RSD() in the file RSD.py: currently the dispersion model is implemented (with both Gaussian and Lorentzian dampings) as well as a halo model based prescription.
fourier module¶
This file contains routines to compute Fourier and Hankel Transforms. They employ the NumPy FFT libraries as well as FFTlog in some cases. They return sorted frequencies for an immediate interpretation of the outcomes. In particular, these routines can be useful to compute two-point correlation functions starting from a power spectrum.
constants module¶
This file is just a compilation of physical constants and does not contain any class or method. While typing help(constants) will provide the list of quantities, it will not be documented. To obtain a full description of the quantities, type in a Python session or program:
import constants
constants.explanatory()
useful_functions module¶
The file contains (as is obvious) useful functions such as extrapolation of arrays and top-hat window functions.
Tests¶
Together with the files, two folders containing some useful and explanatory tests and Python example notebooks are provided. Each of them is adequately commented, so check them out and run them!
Otherwise, you may want to go the Basic usage of cosmological functions section.