Cosmology Module¶

cosmo is a cosmology module build on astropy.Cosmology object specifically for use with 21cm observations.

The default cosmology assumed for these calculations is Planck15.

Relevent Cosmology units and transforms for Power Spectrum estimation.

All cosmological calculations and converions follow from Liu et al 2014a Phys. Rev. D 90, 023018 or arXiv:1404.2596

simpleDS.cosmo.X2Y(z, cosmo=None)[source]¶

Convert units from interferometric delay power to comsological power.

Converts power spectrum from interferometric units of eta, u to cosmological k_par, k_perp.

Parameters

z (float) – redshift for cosmological conversion
cosmo (Astropy Cosmology Object) – The assumed cosmology of the universe. Defaults to WMAP9 year in “little h” units

Returns

X2Y – The power spectrum unit conversion factor

Return type

Astropy Quantity units of Mpc^3*s/sr

simpleDS.cosmo.calc_freq(redshift)[source]¶

Calculate the frequency or frequencies of a given 21cm redshift.

Parameters: redshift (float) – The redshift of the expected 21cm emission
Returns: freq – Frequency of the emission in the rest frame of emission
Return type: Astropy Quantity Object units equivalent to frequency

simpleDS.cosmo.calc_z(freq)[source]¶

Calculate the redshift from a given frequency or frequncies.

Parameters: freq (Astropy Quantity Object units equivalent to frequency) – The frequency to calculate the redshift of 21cm emission
Returns: redshift – The redshift consistent with 21cm observations of the input frequency.
Return type: float

simpleDS.cosmo.eta2kparr(eta, z, cosmo=None)[source]¶

Conver delay eta to k_parallel (comoving 1./Mpc along line of sight).

Parameters

eta (Astropy Quantity object with units equivalent to time.) – The inteferometric delay observed in units compatible with time.
z (float) – The redshift of the expected 21cm emission.
cosmo (Astropy Cosmology Object) – The assumed cosmology of the universe. Defaults to WMAP9 year in “little h” units

Returns

kparr – The spatial fluctuation scale parallel to the line of sight probed by the input delay (eta).

Return type

Astropy Quantity units equivalent to wavenumber

simpleDS.cosmo.kparr2eta(kparr, z, cosmo=None)[source]¶

Convert k_parallel (comoving 1/Mpc along line of sight) to delay eta.

Parameters

kparr (Astropy Quantity units equivalent to wavenumber) – The spatial fluctuation scale parallel to the line of sight
z (float) – The redshift of the expected 21cm emission.
cosmo (Astropy Cosmology Object) – The assumed cosmology of the universe. Defaults to WMAP9 year in “little h” units

Returns

eta – The inteferometric delay which probes the spatial scale given by kparr.

Return type

Astropy Quantity units equivalent to time

simpleDS.cosmo.kperp2u(kperp, z, cosmo=None)[source]¶

Convert comsological k_perpendicular to baseline length u.

Parameters

kperp (Astropy Quantity units equivalent to wavenumber) – The spatial fluctuation scale perpendicular to the line of sight.
z (float) – The redshift of the expected 21cm emission.
cosmo (Astropy Cosmology Object) – The assumed cosmology of the universe. Defaults to WMAP9 year in “little h” units

Returns

u – The baseline separation of two interferometric antennas in units of wavelength which probes the spatial scale given by kperp

Return type

float

simpleDS.cosmo.u2kperp(u, z, cosmo=None)[source]¶

Convert baseline length u to k_perpendicular.

Parameters

u (float) – The baseline separation of two interferometric antennas in units of wavelength
z (float) – The redshift of the expected 21cm emission.
cosmo (Astropy Cosmology Object) – The assumed cosmology of the universe. Defaults to WMAP9 year in “little h” units

Returns

kperp – The spatial fluctuation scale perpendicular to the line of sight probed by the baseline length u.

Return type

Astropy Quantity units equivalent to wavenumber