Source code for hierarc.Likelihood.LensLikelihood.ddt_gauss_likelihood
[docs]
class DdtGaussianLikelihood(object):
"""Class to handle cosmographic likelihood coming from modeling lenses with imaging
and kinematic data but no time delays. Thus Ddt is not constrained but the
kinematics can constrain Ds/Dds.
The current version includes a Gaussian in Ds/Dds but can be extended.
"""
def __init__(self, z_lens, z_source, ddt_mean, ddt_sigma):
"""
:param z_lens: lens redshift
:param z_source: source redshift
:param ddt_mean: mean of Ddt distance
:param ddt_sigma: 1-sigma uncertainty in the Ddt distance
"""
self._z_lens = z_lens
self._ddt_mean = ddt_mean
self._ddt_sigma = ddt_sigma
self._ddt_sigma2 = ddt_sigma**2
self.num_data = 1
[docs]
def log_likelihood(self, ddt, dd=None):
"""
:param ddt: time-delay distance
:param dd: angular diameter distance to the deflector
:return: log likelihood given the single lens analysis
"""
return -((ddt - self._ddt_mean) ** 2) / self._ddt_sigma2 / 2
[docs]
def ddt_measurement(self):
"""
:return: mean, 1-sigma of the ddt inference/model measurement
"""
return self._ddt_mean, self._ddt_sigma