def setCosmology(self, cosmodef):
if type(cosmodef) is dict:
self.cosmo = cosmology.FlatLambdaCDM(**cosmodef)
elif isinstance(cosmodef, basestring):
self.cosmo = cosmology.FlatLambdaCDM(**eval(cosmodef))
elif isinstance(cosmodef, cosmology.FLRW):
self.cosmo = cosmodef
elif cosmodef is None:
self.cosmo = cosmology.get_current()
else:
raise ValueError
def deltavir(redshift, cosmo=None):
""" The virial overdensity as a function redshift.
This is an approximation parameterized by Bryan & Norman 98, ApJ,
495, 80. Good to 1% for omega(z) = 0.1-1, requires either omega =
1 (flat universe) or omega_lambda = 0.
This is given by dissipationless spherical top-hat models of
gravitational collapse (Peebles 1990 'The Large Scale structure of
the Universe', Eke et al. 1996 MNRAS, 282, 263).
"""
if cosmo is None:
cosmo = cosmology.get_current()
if cosmo.Ok0 != 0:
if cosmo.Ode0 == 0:
x = cosmo.Om(redshift) - 1
return 18 * np.pi**2 + 60 * x - 32 * x**2
else:
raise ValueError("Can't compute deltavir for a non-flat cosmology "
"with a cosmological constant")
else:
x = cosmo.Om(redshift) - 1
return 18 * np.pi**2 + 82 * x - 39 * x**2
def deltavir(redshift, cosmo=None):
""" The virial overdensity as a function redshift.
This is an approximation parameterized by Bryan & Norman 98, ApJ,
495, 80. Good to 1% for omega(z) = 0.1-1, requires either omega =
1 (flat universe) or omega_lambda = 0.
This is given by dissipationless spherical top-hat models of
gravitational collapse (Peebles 1990 'The Large Scale structure of
the Universe', Eke et al. 1996 MNRAS, 282, 263).
"""
if cosmo is None:
cosmo = cosmology.get_current()
if cosmo.Ok0 != 0:
if cosmo.Ode0 == 0:
x = cosmo.Om(redshift) - 1
return 18*pi**2 + 60*x - 32*x**2
else:
raise ValueError("Can't compute deltavir for a non-flat cosmology "
"with a cosmological constant")
else:
x = cosmo.Om(redshift) - 1
return 18*pi**2 + 82*x - 39*x**2
def redshifted_to(self, z, adjust_flux=False, dist=None, cosmo=None):
"""Return a new Spectrum object at a new redshift.
The current redshift must be defined (self.z cannot be `None`).
A factor of (1 + z) / (1 + self.z) is applied to the wavelength.
The inverse factor is applied to the flux so that the bolometric
flux (e.g., erg/s/cm^2) remains constant.
.. note:: Currently this only works for units in ergs.
Parameters
----------
z : float
Target redshift.
adjust_flux : bool, optional
If True, the bolometric flux is adjusted by
``F_out = F_in * (D_in / D_out) ** 2``, where ``D_in`` and
``D_out`` are current and target luminosity distances,
respectively. ``D_in`` is self.dist. If self.dist is ``None``,
the distance is calculated from the current redshift and
given cosmology.
dist : float, optional
Output distance in Mpc. Used to adjust bolometric flux if
``adjust_flux`` is ``True``. Default is ``None`` which means
that the distance is calculated from the redshift and the
cosmology.
cosmo : `~astropy.cosmology.Cosmology` instance, optional
The cosmology used to estimate distances if dist is not given.
Default is ``None``, which results in using the default
cosmology.
Returns
-------
spec : Spectrum object
A new spectrum object at redshift z.
"""
if self._z is None:
raise ValueError('Must set current redshift in order to redshift'
' spectrum')
if self._wunit.physical_type == u.m.physical_type:
factor = (1. + z) / (1. + self._z)
elif self._wunit.physical_type == u.Hz.physical_type:
factor = (1. + self._z) / (1. + z)
else:
raise ValueError('wavelength must be in wavelength or frequency')
d = self._wave * factor
f = self._flux / factor
if self._error is not None:
e = self._error / factor
else:
e = None
if adjust_flux:
if self._dist is None and self._z == 0.:
raise ValueError("When current redshift is 0 and adjust_flux "
"is requested, current distance must be "
"defined")
if dist is None and z == 0.:
raise ValueError("When redshift is 0 and adjust_flux "
"is requested, dist must be defined")
if cosmo is None:
cosmo = cosmology.get_current()
if self._dist is None:
dist_in = cosmo.luminosity_distance(self._z)
else:
dist_in = self._dist
if dist is None:
dist = cosmo.luminosity_distance(z)
if dist_in <= 0. or dist <= 0.:
raise ValueError("Distances must be greater than 0.")
# Adjust the flux
factor = (dist_in / dist) ** 2
f *= factor
if e is not None:
e *= factor
return Spectrum(d, f, error=e, z=z, dist=dist, meta=self.meta,
unit=self._unit, wave_unit=self._wunit)
def find_rvT(M, z, cosmo=None, mu=0.59):
""" Find the virial radius, circular velocity and temperature for
a dark matter halo at a given mass and redshift.
Parameters
----------
mass : array_like, shape N
Total halo mass (including dark matter) in solar masses.
z : array_like, shape M
Redshift.
cosmo : cosmology (optional)
The cosmology to use.
mu : float (optional)
The mean molecular weight. The virial temperature is
proportional to mu.
Returns
-------
vir : named tuple of ndarrays with shape (N, M)
The virial radius (proper kpc), circular velocity (km/s) and
temperature (K). If N or M is 1, that dimension is suppressed.
Notes
-----
The value of mu depends on the ionization fraction of the gas; mu
= 0.59 for a fully ionized primordial gas (the default), mu = 0.61
for a gas with ionized hydrogen but only singly ionized helium,
and mu = 1.22 for neutral primordial gas.
Examples
--------
>>> vir = find_rvT(1e12, 0)
>>> print vir.r, vir.v, vir.T
261.195728743 128.338776885 588643.476006
>>> r,v,T = find_rvT(1e12, [0.5, 1, 1.5, 2])
>>> r
array([ 198.57846074, 156.44358398, 127.91018732, 107.74327378])
>>> v
array([ 147.1888328 , 165.82959995, 183.39536858, 199.82317152])
>>> T
array([ 774259.0063081 , 982789.81965216, 1202024.36495813,
1427014.0148491 ])
"""
if isiterable(M):
M = np.asarray(M)
if cosmo is None:
cosmo = cosmology.get_current()
# convert to cgs
M_g = M * Msun
crit_dens = cosmo.critical_density(z)
if astropy.__version__ >= '0.3':
crit_dens = crit_dens.value#to('g/cm^3').value
rho_virial = deltavir(z, cosmo=cosmo) * crit_dens
# deal with cases where we have two input arrays
if isiterable(M) and isiterable(rho_virial):
M_g = np.atleast_2d(M_g).T
rho_virial = np.atleast_2d(rho_virial)
rvir, vcirc, Tvir = _calc_rvT(M_g, rho_virial, mu=mu)
return find_rvT_output(r=rvir/kpc, v=vcirc/km, T=Tvir)
def find_rvT(M, z, cosmo=None, mu=0.59):
""" Find the virial radius, circular velocity and temperature for
a dark matter halo at a given mass and redshift.
Parameters
----------
mass : array_like, shape N
Total halo mass (including dark matter) in solar masses.
z : array_like, shape M
Redshift.
cosmo : cosmology (optional)
The cosmology to use.
mu : float (optional)
The mean molecular weight. The virial temperature is
proportional to mu.
Returns
-------
vir : named tuple of ndarrays with shape (N, M)
The virial radius (proper kpc), circular velocity (km/s) and
temperature (K). If N or M is 1, that dimension is suppressed.
Notes
-----
The value of mu depends on the ionization fraction of the gas; mu
= 0.59 for a fully ionized primordial gas (the default), mu = 0.61
for a gas with ionized hydrogen but only singly ionized helium,
and mu = 1.22 for neutral primordial gas.
Examples
--------
>>> vir = find_rvT(1e12, 0)
>>> print vir.r, vir.v, vir.T
261.195728743 128.338776885 588643.476006
>>> r,v,T = find_rvT(1e12, [0.5, 1, 1.5, 2])
>>> r
array([ 198.57846074, 156.44358398, 127.91018732, 107.74327378])
>>> v
array([ 147.1888328 , 165.82959995, 183.39536858, 199.82317152])
>>> T
array([ 774259.0063081 , 982789.81965216, 1202024.36495813,
1427014.0148491 ])
"""
if isiterable(M):
M = np.asarray(M)
if cosmo is None:
cosmo = cosmology.get_current()
# convert to cgs
M_g = M * Msun
crit_dens = cosmo.critical_density(z)
if astropy.__version__ >= '0.3':
crit_dens = crit_dens.value #to('g/cm^3').value
rho_virial = deltavir(z, cosmo=cosmo) * crit_dens
# deal with cases where we have two input arrays
if isiterable(M) and isiterable(rho_virial):
M_g = np.atleast_2d(M_g).T
rho_virial = np.atleast_2d(rho_virial)
rvir, vcirc, Tvir = _calc_rvT(M_g, rho_virial, mu=mu)
return find_rvT_output(r=rvir / kpc, v=vcirc / km, T=Tvir)
