Matter shell definition

This example demonstrates how matter shells are defined, and their angular power spectra computed.

The the angular power spectra are saved here, so that they can be reused in other examples without recomputing.

Compute

Here we define the shells for these examples, and use CAMB to compute the angular matter power spectra for the shell definitions.

import numpy as np
import camb
from cosmology import Cosmology

import glass.shells
import glass.ext.camb


# cosmology for the simulation
h = 0.7
Oc = 0.25
Ob = 0.05

# basic parameters of the simulation
lmax = 1000

# set up CAMB parameters for matter angular power spectrum
pars = camb.set_params(H0=100*h, omch2=Oc*h**2, ombh2=Ob*h**2,
                       NonLinear=camb.model.NonLinear_both)

# get the cosmology from CAMB
cosmo = Cosmology.from_camb(pars)

# shells of 200 Mpc in comoving distance spacing
zb = glass.shells.distance_grid(cosmo, 0., 1., dx=200.)

# uniform matter weight function
# CAMB requires linear ramp for low redshifts
ws = glass.shells.tophat_windows(zb, weight=glass.ext.camb.camb_tophat_weight)

# compute angular matter power spectra with CAMB
cls = glass.ext.camb.matter_cls(pars, lmax, ws)

Save

We save the shell definitions to file, for use in other examples.

np.save('cls.npy', cls)