Source code for astropy.cosmology.flrw.w0cdm

# Licensed under a 3-clause BSD style license - see LICENSE.rst

import numpy as np
from numpy import sqrt

import astropy.units as u
from astropy.cosmology.parameter import Parameter
from astropy.cosmology.utils import aszarr

from . import scalar_inv_efuncs
from .base import FLRW, FlatFLRWMixin

__all__ = ["wCDM", "FlatwCDM"]

__doctest_requires__ = {'*': ['scipy']}


[docs]class wCDM(FLRW): """ FLRW cosmology with a constant dark energy equation of state and curvature. This has one additional attribute beyond those of FLRW. Parameters ---------- H0 : float or scalar quantity-like ['frequency'] 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. Ode0 : float Omega dark energy: density of dark energy in units of the critical density at z=0. w0 : float, optional Dark energy equation of state at all redshifts. This is pressure/density for dark energy in units where c=1. A cosmological constant has w0=-1.0. Tcmb0 : float or scalar quantity-like ['temperature'], 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-like ['energy', 'mass'] or array-like, optional Mass of each neutrino species in [eV] (mass-energy equivalency enabled). 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 or None (optional, keyword-only) Name for this cosmological object. meta : mapping or None (optional, keyword-only) Metadata for the cosmology, e.g., a reference. Examples -------- >>> from astropy.cosmology import wCDM >>> cosmo = wCDM(H0=70, Om0=0.3, Ode0=0.7, w0=-0.9) The comoving distance in Mpc at redshift z: >>> z = 0.5 >>> dc = cosmo.comoving_distance(z) """ w0 = Parameter(doc="Dark energy equation of state.", fvalidate="float") def __init__(self, H0, Om0, Ode0, w0=-1.0, Tcmb0=0.0*u.K, Neff=3.04, m_nu=0.0*u.eV, Ob0=None, *, name=None, meta=None): super().__init__(H0=H0, Om0=Om0, Ode0=Ode0, Tcmb0=Tcmb0, Neff=Neff, m_nu=m_nu, Ob0=Ob0, name=name, meta=meta) self.w0 = w0 # Please see :ref:`astropy-cosmology-fast-integrals` for discussion # about what is being done here. if self._Tcmb0.value == 0: self._inv_efunc_scalar = scalar_inv_efuncs.wcdm_inv_efunc_norel self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._Ok0, self._w0) elif not self._massivenu: self._inv_efunc_scalar = scalar_inv_efuncs.wcdm_inv_efunc_nomnu self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._Ok0, self._Ogamma0 + self._Onu0, self._w0) else: self._inv_efunc_scalar = scalar_inv_efuncs.wcdm_inv_efunc self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._Ok0, self._Ogamma0, self._neff_per_nu, self._nmasslessnu, self._nu_y_list, self._w0)
[docs] def w(self, z): r"""Returns dark energy equation of state at redshift ``z``. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- w : ndarray or float The dark energy equation of state Returns `float` if the input is scalar. Notes ----- The dark energy equation of state is defined as :math:`w(z) = P(z)/\rho(z)`, where :math:`P(z)` is the pressure at redshift z and :math:`\rho(z)` is the density at redshift z, both in units where c=1. Here this is :math:`w(z) = w_0`. """ z = aszarr(z) return self._w0 * (np.ones(z.shape) if hasattr(z, "shape") else 1.0)
[docs] def de_density_scale(self, z): r"""Evaluates the redshift dependence of the dark energy density. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- I : ndarray or float The scaling of the energy density of dark energy with redshift. Returns `float` if the input is scalar. Notes ----- The scaling factor, I, is defined by :math:`\rho(z) = \rho_0 I`, and in this case is given by :math:`I = \left(1 + z\right)^{3\left(1 + w_0\right)}` """ return (aszarr(z) + 1.0) ** (3.0 * (1. + self._w0))
[docs] def efunc(self, z): """Function used to calculate H(z), the Hubble parameter. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- E : ndarray or float The redshift scaling of the Hubble constant. Returns `float` if the input is scalar. Defined such that :math:`H(z) = H_0 E(z)`. """ Or = self._Ogamma0 + (self._Onu0 if not self._massivenu else self._Ogamma0 * self.nu_relative_density(z)) zp1 = aszarr(z) + 1.0 # (converts z [unit] -> z [dimensionless]) return sqrt(zp1 ** 2 * ((Or * zp1 + self._Om0) * zp1 + self._Ok0) + self._Ode0 * zp1 ** (3. * (1. + self._w0)))
[docs] def inv_efunc(self, z): r"""Function used to calculate :math:`\frac{1}{H_z}`. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- E : ndarray or float The inverse redshift scaling of the Hubble constant. Returns `float` if the input is scalar. Defined such that :math:`H_z = H_0 / E`. """ Or = self._Ogamma0 + (self._Onu0 if not self._massivenu else self._Ogamma0 * self.nu_relative_density(z)) zp1 = aszarr(z) + 1.0 # (converts z [unit] -> z [dimensionless]) return (zp1 ** 2 * ((Or * zp1 + self._Om0) * zp1 + self._Ok0) + self._Ode0 * zp1 ** (3. * (1. + self._w0)))**(-0.5)
[docs]class FlatwCDM(FlatFLRWMixin, wCDM): """ FLRW cosmology with a constant dark energy equation of state and no spatial curvature. This has one additional attribute beyond those of FLRW. Parameters ---------- H0 : float or scalar quantity-like ['frequency'] 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. w0 : float, optional Dark energy equation of state at all redshifts. This is pressure/density for dark energy in units where c=1. A cosmological constant has w0=-1.0. Tcmb0 : float or scalar quantity-like ['temperature'], 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-like ['energy', 'mass'] or array-like, optional Mass of each neutrino species in [eV] (mass-energy equivalency enabled). 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 or None (optional, keyword-only) Name for this cosmological object. meta : mapping or None (optional, keyword-only) Metadata for the cosmology, e.g., a reference. Examples -------- >>> from astropy.cosmology import FlatwCDM >>> cosmo = FlatwCDM(H0=70, Om0=0.3, w0=-0.9) The comoving distance in Mpc at redshift z: >>> z = 0.5 >>> dc = cosmo.comoving_distance(z) To get an equivalent cosmology, but of type `astropy.cosmology.wCDM`, use :attr:`astropy.cosmology.FlatFLRWMixin.nonflat`. >>> cosmo.nonflat wCDM(H0=70.0 km / (Mpc s), Om0=0.3, ... """ def __init__(self, H0, Om0, w0=-1.0, Tcmb0=0.0*u.K, Neff=3.04, m_nu=0.0*u.eV, Ob0=None, *, name=None, meta=None): super().__init__(H0=H0, Om0=Om0, Ode0=0.0, w0=w0, Tcmb0=Tcmb0, Neff=Neff, m_nu=m_nu, Ob0=Ob0, name=name, meta=meta) # Please see :ref:`astropy-cosmology-fast-integrals` for discussion # about what is being done here. if self._Tcmb0.value == 0: self._inv_efunc_scalar = scalar_inv_efuncs.fwcdm_inv_efunc_norel self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._w0) elif not self._massivenu: self._inv_efunc_scalar = scalar_inv_efuncs.fwcdm_inv_efunc_nomnu self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._Ogamma0 + self._Onu0, self._w0) else: self._inv_efunc_scalar = scalar_inv_efuncs.fwcdm_inv_efunc self._inv_efunc_scalar_args = (self._Om0, self._Ode0, self._Ogamma0, self._neff_per_nu, self._nmasslessnu, self._nu_y_list, self._w0)
[docs] def efunc(self, z): """Function used to calculate H(z), the Hubble parameter. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- E : ndarray or float The redshift scaling of the Hubble constant. Returns `float` if the input is scalar. Defined such that :math:`H(z) = H_0 E(z)`. """ Or = self._Ogamma0 + (self._Onu0 if not self._massivenu else self._Ogamma0 * self.nu_relative_density(z)) zp1 = aszarr(z) + 1.0 # (converts z [unit] -> z [dimensionless]) return sqrt(zp1 ** 3 * (Or * zp1 + self._Om0) + self._Ode0 * zp1 ** (3.0 * (1 + self._w0)))
[docs] def inv_efunc(self, z): r"""Function used to calculate :math:`\frac{1}{H_z}`. Parameters ---------- z : Quantity-like ['redshift'], array-like, or `~numbers.Number` Input redshift. Returns ------- E : ndarray or float The inverse redshift scaling of the Hubble constant. Returns `float` if the input is scalar. Defined such that :math:`H(z) = H_0 E(z)`. """ Or = self._Ogamma0 + (self._Onu0 if not self._massivenu else self._Ogamma0 * self.nu_relative_density(z)) zp1 = aszarr(z) + 1.0 # (converts z [unit] -> z [dimensionless]) return (zp1 ** 3 * (Or * zp1 + self._Om0) + self._Ode0 * zp1 ** (3. * (1. + self._w0)))**(-0.5)