Source code for lenstronomy.Cosmo.background

from __future__ import print_function, division, absolute_import, unicode_literals
__author__ = 'sibirrer'

import numpy as np
import lenstronomy.Util.constants as const
from lenstronomy.Cosmo.cosmo_interp import CosmoInterp

__all__ = ['Background']


[docs]class Background(object): """ class to compute cosmological distances """ def __init__(self, cosmo=None, interp=False, **kwargs_interp): """ :param cosmo: instance of astropy.cosmology :param interp: boolean, if True, uses interpolated cosmology to evaluate specific redshifts :param kwargs_interp: keyword arguments of CosmoInterp specifying the interpolation interval and maximum redshift :return: Background class with instance of astropy.cosmology """ if cosmo is None: from astropy.cosmology import default_cosmology cosmo = default_cosmology.get() if interp: self.cosmo = CosmoInterp(cosmo, **kwargs_interp) else: self.cosmo = cosmo
[docs] def a_z(self, z): """ returns scale factor (a_0 = 1) for given redshift :param z: redshift :return: scale factor """ return 1./(1+z)
[docs] def d_xy(self, z_observer, z_source): """ :param z_observer: observer redshift :param z_source: source redshift :return: angular diameter distance in units of Mpc """ D_xy = self.cosmo.angular_diameter_distance_z1z2(z_observer, z_source) return D_xy.value
[docs] def ddt(self, z_lens, z_source): """ time-delay distance :param z_lens: redshift of lens :param z_source: redshift of source :return: time-delay distance in units of proper Mpc """ return self.d_xy(0, z_lens) * self.d_xy(0, z_source) / self.d_xy(z_lens, z_source) * (1 + z_lens)
[docs] def T_xy(self, z_observer, z_source): """ :param z_observer: observer :param z_source: source :return: transverse comoving distance in units of Mpc """ D_xy = self.d_xy(z_observer, z_source) T_xy = D_xy * (1 + z_source) return T_xy
@property def rho_crit(self): """ critical density :return: value in M_sol/Mpc^3 """ h = self.cosmo.H(0).value / 100. return 3 * h ** 2 / (8 * np.pi * const.G) * 10 ** 10 * const.Mpc / const.M_sun