CosmoFit.cosmology.SoundHorizon

class CosmoFit.cosmology.SoundHorizon(cosmology)

Bases: object

The sound horizon at the drag epoch for a given cosmology.

Parameters:

cosmology (Cosmology) – Reads Omega_m, Omega_b, H0, N_eff and m_nu. Nothing else – r_d is blind to the dark-energy model and to curvature (see the module docstring).

Notes

rd returns the free parameter unless the cosmology has compute_rd set, in which case it returns rd_computed(). rd_computed() is always available regardless, so the computed value can be compared against a fitted one without changing how a fit behaves.

Results are cached on the physical densities they depend on, so the BAO likelihoods – which ask for rd once per data point – pay for the integral once per MCMC step rather than thirteen times.

__init__(cosmology)

Methods

__init__(cosmology)
hubble_over_h100(a)	H(a) / (100 km/s/Mpc) in the pre-recombination universe: photons, neutrinos and cold matter.
omega_nu_of_a(a)	Total neutrino density (massless plus massive) at scale factor a, as it enters H(a)^2 / H_100^2.
rd_computed()	The sound horizon at the drag epoch [Mpc], computed from the physical densities.
sound_horizon([z, n_grid, decades])	Comoving sound horizon [Mpc] at redshift z,
sound_speed(a)	Baryon-photon sound speed [km/s],
summary()	z_drag, r_d, and the densities they came from, in one dict -- for checking a fit's early-universe sector without reconstructing the calculation by hand.
z_drag()	Redshift of the baryon drag epoch, from a fit calibrated against CAMB (see _ZDRAG_COEF).
z_drag_eh98()	Drag-epoch redshift from the Eisenstein & Hu (1998) Eq.

Attributes

h	Reduced Hubble constant, H0 / 100.
n_massive	one carrying the whole of Sum m_nu (CAMB's degenerate default), or zero when m_nu = 0.
omega_b	Physical baryon density, Omega_b h^2.
omega_cb	Physical cold-matter density, (Omega_c + Omega_b) h^2.
omega_gamma	Physical photon density, from T_CMB.
omega_nu	Present-day massive-neutrino density, Omega_nu h^2.
rd	the free rd parameter by default, or rd_computed() when the cosmology has compute_rd set.