FlatLambdaCDM

class astropy.cosmology.FlatLambdaCDM(H0, Om0, Tcmb0=0, Neff=3.04, m_nu=<Quantity 0. eV>, Ob0=None, name=None)

Bases: astropy.cosmology.LambdaCDM

FLRW cosmology with a cosmological constant and no curvature.

This has no additional attributes beyond those of FLRW.

Parameters:

H0 : float or Quantity

Hubble constant at z = 0. If a float, must be in [km/sec/Mpc]

Om0 : float

Omega matter: density of non-relativistic matter in units of the critical density at z=0.

Tcmb0 : float or scalar Quantity, optional

Temperature of the CMB z=0. If a float, must be in [K]. Default: 0 [K]. Setting this to zero will turn off both photons and neutrinos (even massive ones).

Neff : float, optional

Effective number of Neutrino species. Default 3.04.

m_nu : Quantity, optional

Mass of each neutrino species. If this is a scalar Quantity, then all neutrino species are assumed to have that mass. Otherwise, the mass of each species. The actual number of neutrino species (and hence the number of elements of m_nu if it is not scalar) must be the floor of Neff. Typically this means you should provide three neutrino masses unless you are considering something like a sterile neutrino.

Ob0 : float or None, optional

Omega baryons: density of baryonic matter in units of the critical density at z=0. If this is set to None (the default), any computation that requires its value will raise an exception.

name : str, optional

Name for this cosmological object.

Examples

>>> from astropy.cosmology import FlatLambdaCDM
>>> cosmo = FlatLambdaCDM(H0=70, Om0=0.3)

The comoving distance in Mpc at redshift z:

>>> z = 0.5
>>> dc = cosmo.comoving_distance(z)

Methods Summary

efunc(z)	Function used to calculate H(z), the Hubble parameter.
inv_efunc(z)	Function used to calculate \(\frac{1}{H_z}\).

Methods Documentation

efunc(z)

Function used to calculate H(z), the Hubble parameter.

Parameters:

z : array-like

Input redshifts.

Returns:

E : ndarray, or float if input scalar

The redshift scaling of the Hubble constant.

Notes

The return value, E, is defined such that \(H(z) = H_0 E\).

inv_efunc(z)

Function used to calculate \(\frac{1}{H_z}\).

Parameters:

z : array-like

Input redshifts.

Returns:

E : ndarray, or float if input scalar

The inverse redshift scaling of the Hubble constant.

Notes

The return value, E, is defined such that \(H_z = H_0 / E\).