/usr/lib/python2.7/dist-packages/astroML/cosmology.py is in python-astroml 0.3-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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from scipy import integrate
class Cosmology(object):
"""Class to enable simple cosmological calculations.
For a more full-featured cosmology package, see CosmoloPy [1]_
Parameters
----------
omegaM : float
Matter Density. 0 <= omegaM <= 1
omegaL : float
Dark energy density. 0 <= omegaL <= 1
h : float
Hubble parameter, in units of 100 km/s/Mpc
References
----------
[1] http://roban.github.com/CosmoloPy/
"""
def __init__(self, omegaM=0.27, omegaL=0.73, h=0.71):
self.omegaM = omegaM
self.omegaL = omegaL
self.omegaK = 1. - omegaM - omegaL
self.h = h
# compute hubble distance in Mpc
self.Dh = 2.9979E5 / (100 * h)
def _hinv(self, z):
"""
dimensionless Hubble constant at redshift z
This is used in integration routines
Defined as in equation 14 from Hogg 1999, and modified
for non-constant w parameterized linearly with z ( w = w0 + w1*z )
"""
if np.isinf(z):
return np.inf
return np.sqrt(self.omegaM * (1. + z) ** 3
+ self.omegaK * (1. + z) ** 2
+ self.omegaL)
def Dc(self, z):
"""
Line of sight comoving distance at redshift z
Remains constant with epoch if objects are in the Hubble flow
"""
if z == 0:
return 0
else:
f = lambda z: 1.0 / self._hinv(z)
I = integrate.quad(f, 0, z)
return self.Dh * I[0]
def Dm(self, z):
"""
Transverse comoving distance at redshift z
At same redshift but separated by angle dtheta;
Dm * dtheta is transverse comoving distance
"""
sOk = np.sqrt(abs(self.omegaK))
if self.omegaK < 0.0:
return self.Dh * np.sin(sOk * self.Dc(z) / self.Dh) / sOk
elif self.omegaK == 0.0:
return self.Dc(z)
else:
return self.Dh * np.sinh(sOk * self.Dc(z) / self.Dh) / sOk
def Dl(self, z):
"""Luminosity distance (Mpc) at redshift z"""
return (1. + z) * self.Dm(z)
def mu(self, z):
"""Distance Modulus at redshift z"""
return 5. * np.log10(self.Dl(z) * 1E6) - 5.
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