LambdaCDM¶

class
astropy.cosmology.
LambdaCDM
(H0, Om0, Ode0, Tcmb0=0, Neff=3.04, m_nu=<Quantity 0. eV>, Ob0=None, name=None)[source] [edit on github]¶ Bases:
astropy.cosmology.FLRW
FLRW cosmology with a cosmological constant and 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 nonrelativistic matter in units of the critical density at z=0.
 Ode0 : float
Omega dark energy: density of the cosmological constant 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 LambdaCDM >>> cosmo = LambdaCDM(H0=70, Om0=0.3, Ode0=0.7)
The comoving distance in Mpc at redshift z:
>>> z = 0.5 >>> dc = cosmo.comoving_distance(z)
Methods Summary
de_density_scale
(z)Evaluates the redshift dependence of the dark energy density. efunc
(z)Function used to calculate H(z), the Hubble parameter. inv_efunc
(z)Function used to calculate \(\frac{1}{H_z}\). w
(z)Returns dark energy equation of state at redshift z
.Methods Documentation

de_density_scale
(z)[source] [edit on github]¶ Evaluates the redshift dependence of the dark energy density.
Parameters:  z : arraylike
Input redshifts.
Returns:  I : ndarray, or float if input scalar
The scaling of the energy density of dark energy with redshift.
Notes
The scaling factor, I, is defined by \(\rho(z) = \rho_0 I\), and in this case is given by \(I = 1\).

efunc
(z)[source] [edit on github]¶ Function used to calculate H(z), the Hubble parameter.
Parameters:  z : arraylike
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)[source] [edit on github]¶ Function used to calculate \(\frac{1}{H_z}\).
Parameters:  z : arraylike
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 \(H_z = H_0 / E\).

w
(z)[source] [edit on github]¶ Returns dark energy equation of state at redshift
z
.Parameters:  z : arraylike
Input redshifts.
Returns:  w : ndarray, or float if input scalar
The dark energy equation of state
Notes
The dark energy equation of state is defined as \(w(z) = P(z)/\rho(z)\), where \(P(z)\) is the pressure at redshift z and \(\rho(z)\) is the density at redshift z, both in units where c=1. Here this is \(w(z) = 1\).
 H0 : float or