nbodykit.cosmology.power.linear¶
Functions
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Classes
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An object to compute the linear power spectrum and related quantities, using a transfer function from the CLASS code or the analytic Eisenstein & Hu approximation. |
- class nbodykit.cosmology.power.linear.LinearPower(cosmo, redshift, transfer='CLASS')[source]¶
An object to compute the linear power spectrum and related quantities, using a transfer function from the CLASS code or the analytic Eisenstein & Hu approximation.
- Parameters
cosmo (
Cosmology
, astropy.cosmology.FLRW) – the cosmology instance; astropy cosmology objects are automatically converted to the proper typeredshift (float) – the redshift of the power spectrum
transfer (str, optional) – string specifying the transfer function to use; one of ‘CLASS’, ‘EisensteinHu’, ‘NoWiggleEisensteinHu’
- cosmo¶
the object giving the cosmological parameters
- Type
class:Cosmology
- Attributes
Methods
__call__
(k)Return the linear power spectrum in units of \(h^{-3} \mathrm{Mpc}^3\) at the redshift specified by
redshift
.sigma_r
(r[, kmin, kmax])The mass fluctuation within a sphere of radius
r
, in units of \(h^{-1} Mpc\) atredshift
.velocity_dispersion
([kmin, kmax])The velocity dispersion in units of of \(\mathrm{Mpc/h}\) at
redshift
.- __call__(k)[source]¶
Return the linear power spectrum in units of \(h^{-3} \mathrm{Mpc}^3\) at the redshift specified by
redshift
.The transfer function used to evaluate the power spectrum is specified by the
transfer
attribute.
- property attrs¶
The meta-data dictionary
- property redshift¶
The redshift of the power spectrum
- property sigma8¶
The present day value of
sigma_r(r=8 Mpc/h)
, used to normalize the power spectrum, which is proportional to the square of this value.The power spectrum can re-normalized by setting a different value for this parameter
- sigma_r(r, kmin=1e-05, kmax=10.0)[source]¶
The mass fluctuation within a sphere of radius
r
, in units of \(h^{-1} Mpc\) atredshift
.This returns \(\sigma\), where
\[\sigma^2 = \int_0^\infty \frac{k^3 P(k,z)}{2\pi^2} W^2_T(kr) \frac{dk}{k},\]where \(W_T(x) = 3/x^3 (\mathrm{sin}x - x\mathrm{cos}x)\) is a top-hat filter in Fourier space.
The value of this function with
r=8
returnssigma8
, within numerical precision.