# pyccl.core module¶

The core functionality of ccl, including the core data types. This includes the cosmology and parameters objects used to instantiate a model from which one can compute a set of theoretical predictions.

The classes in this module accept strings indicating which model to use for various physical quantities (e.g., the transfer function). The various options are as follows.

transfer_function options
• ‘emulator’: the transfer function defined by the Comsic Emu
• ‘fitting_function’: the Eisenstein and Hu (1998) fitting function
• ‘eisenstein_hu’: the Eisenstein and Hu (1998) fitting function
• ‘bbks’: the BBKS approximation
• ‘boltzmann’: use CLASS to compute the transfer function
• ‘boltzmann_class’: use CLASS to compute the transfer function
• ‘class’: use CLASS to compute the transfer function
• ‘boltzmann_camb’: not implemented
• ‘camb’: not implemented
matter_power_spectrum options
• ‘halo_model’: use a halo model
• ‘halofit’: use HALOFIT
• ‘linear’: neglect non-linear power spectrum contributions
• ‘emu’: use the Cosmic Emu
baryons_power_spectrum options
• ‘nobaryons’: neglect baryonic contributions to the power spectrum
• ‘bcm’: use the baryonic correction model
mass_function options
• ‘tinker’: the Tinker et al. (2008) mass function
• ‘tinker10’: the Tinker et al. (2010) mass function
• ‘watson’: the Watson et al. mass function
• ‘angulo’: the Angulo et al. mass function
• ‘shethtormen’: the Sheth and Tormen mass function
halo_concentration options
• ‘bhattacharya2011’: Bhattacharya et al. (2011) relation
• ‘duffy2008’: Duffy et al. (2008) relation
• ‘constant_concentration’: use a constant concentration
mnu_type options

This parameter specifies the model for massive neutrinos.

• ‘list’: specify each mass yourself in eV
• ‘sum’: use the normal hierarchy to convert total mass to individual masses
• ‘sum_inverted’: use the inverted hierarchy to convert total mass to individual masses
• ‘sum_equal’: assume equal masses when converting the total mass to individual masses
emulator_neutrinos options

This parameter specifies how to handle inconsistencies in the treatment of neutrinos between the Cosmic Emu (equal masses) and other models.

• ‘strict’: fail unless things are absolutely consistent
• ‘equalize’: redistribute the total mass equaly before using the Cosmic Emu. This option may result in slight internal inconsistencies in the physical model assumed for neutrinos.
class pyccl.core.Cosmology(Omega_c=None, Omega_b=None, h=None, n_s=None, sigma8=None, A_s=None, Omega_k=0.0, Omega_g=None, Neff=3.046, m_nu=0.0, mnu_type=None, w0=-1.0, wa=0.0, bcm_log10Mc=14.079181246047625, bcm_etab=0.5, bcm_ks=55.0, z_mg=None, df_mg=None, transfer_function='boltzmann_class', matter_power_spectrum='halofit', baryons_power_spectrum='nobaryons', mass_function='tinker10', halo_concentration='duffy2008', emulator_neutrinos='strict')[source]

Bases: object

A cosmology including parameters and associated data.

Note

Although some arguments default to None, they will raise a ValueError inside this function if not specified, so they are not optional.

Note

The parameter Omega_g can be used to set the radiation density (not including relativistic neutrinos) to zero. Doing this will give you a model that is physically inconsistent since the temperature of the CMB will still be non-zero. Note however that this approximation is common for late-time LSS computations.

Note

BCM stands for the “baryonic correction model” of Schneider & Teyssier (2015; https://arxiv.org/abs/1510.06034). See the DESC Note for details.

Parameters: Omega_c (float) – Cold dark matter density fraction. Omega_b (float) – Baryonic matter density fraction. h (float) – Hubble constant divided by 100 km/s/Mpc; unitless. A_s (float) – Power spectrum normalization. Exactly one of A_s and sigma_8 is required. sigma8 (float) – Variance of matter density perturbations at an 8 Mpc/h scale. Exactly one of A_s and sigma_8 is required. n_s (float) – Primordial scalar perturbation spectral index. Omega_k (float, optional) – Curvature density fraction. Defaults to 0. Omega_g (float, optional) – Density in relativistic species except massless neutrinos. The default of None corresponds to setting this from the CMB temperature. Note that if a non-None value is given, this may result in a physically inconsistent model because the CMB temperature will still be non-zero in the parameters. Neff (float, optional) – Effective number of massless neutrinos present. Defaults to 3.046. m_nu (float, optional) – Total mass in eV of the massive neutrinos present. Defaults to 0. mnu_type (str, optional) – The type of massive neutrinos. w0 (float, optional) – First order term of dark energy equation of state. Defaults to -1. wa (float, optional) – Second order term of dark energy equation of state. Defaults to 0. bcm_log10Mc (float, optional) – One of the parameters of the BCM model. Defaults to np.log10(1.2e14). bcm_etab (float, optional) – One of the parameters of the BCM model. Defaults to 0.5. bcm_ks (float, optional) – One of the parameters of the BCM model. Defaults to 55.0. df_mg (array_like, optional) – Perturbations to the GR growth rate as a function of redshift $$\Delta f$$. Used to implement simple modified growth scenarios. z_mg (array_like, optional) – Array of redshifts corresponding to df_mg. transfer_function (str, optional) – The transfer function to use. Defaults to ‘boltzmann_class’. matter_power_spectrum (str, optional) – The matter power spectrum to use. Defaults to ‘halofit’. baryons_power_spectrum (str, optional) – The correction from baryonic effects to be implemented. Defaults to ‘nobaryons’. mass_function (str, optional) – The mass function to use. Defaults to ‘tinker10’ (2010). halo_concentration (str, optional) – The halo concentration relation to use. Defaults to Duffy et al. (2008) ‘duffy2008’. emulator_neutrinos – str, optional): If using the emulator for the power spectrum, specified treatment of unequal neutrinos. Options are ‘strict’, which will raise an error and quit if the user fails to pass either a set of three equal masses or a sum with mnu_type = ‘sum_equal’, and ‘equalize’, which will redistribute masses to be equal right before calling the emualtor but results in internal inconsistencies. Defaults to ‘strict’.
compute_distances()[source]

Compute the distance splines.

compute_growth()[source]

Compute the growth function.

compute_power()[source]

Compute the power spectrum.

has_distances()[source]

Checks if the distances have been precomputed.

Returns: True if precomputed, False otherwise. bool
has_growth()[source]

Checks if the growth function has been precomputed.

Returns: True if precomputed, False otherwise. bool
has_power()[source]

Checks if the power spectra have been precomputed.

Returns: True if precomputed, False otherwise. bool
has_sigma()[source]

Checks if sigma8 has been computed.

Returns: True if precomputed, False otherwise. bool
classmethod read_yaml(filename)[source]

Read the parameters from a YAML file.

Parameters: filename (str) –
status()[source]

Get error status of the ccl_cosmology object.

Note

error statuses are currently under development.

Returns: str containing the status message.
write_yaml(filename)[source]

Write a YAML representation of the parameters to file.

Parameters: filename (str) –
pyccl.core.check(status, cosmo=None)[source]

Check the status returned by a ccllib function.

Parameters: status (int or core.error_types) – Flag or error describing the success of a function.