Map transform (map_transform)

Transform discrete catalogues to Fourier-space map data.

SphericalMap(catalogues, disc[, initialise])

Discretised spherical Fourier map from catalogue sources.

CartesianMap(catalogues, orders[, kmin, ...])

Compressed Cartesian Fourier-space map from catalogue sources.

class harmonia.mapper.map_transform.SphericalMap(catalogues, disc, initialise=True)[source]

Discretised spherical Fourier map from catalogue sources.

Parameters:

  • catalogues (SphericalFKPCatalogue) – FKP-style paired catalogues in a spherical domain.

  • disc (DiscreteSpectrum) – Discrete spectrum for the map.

  • initialise (bool, optional) – If True (default), map transform is performed upon creation.

Variables:

  • catalogues (SphericalFKPCatalogue) – FKP-style paired catalogues associated with the map.

  • disc (DiscreteSpectrum) – Discrete spectrum associated with the map.

  • attrs (dict) – Attributes inherited upon creation.

property density_contrast

Spherical Fourier coefficients for the density contrast between data and random catalogues.

Notes

When the spherical map is initialsed upon creation or this is directly or indirectly accessed without initialising the spherical map upon creation, discrete spherical Fourier transform is performed by direct summation over all selected objects in the paired catalogues.

Calling this method stores the transformed number densities of data and random catalogues internally for further processing, e.g. for mode_power(). Computational redundancy is reduced by employing parity relations between spherical harmonics of the same degree but opposite orders.

Returns:

Density contrast coefficients of the spherical map.

Return type:

SphericalArray

property mode_power

Spherical Fourier mode power suitably normalised.

In the simplest case of a full-sky statistically isotropic map without any mode coupling, this is equivalent to the Cartesian power spectrum at the same wavenumbers.

Returns:

Spherical mode power at discrete mode wavenumbers with mode counts and indices.

Return type:

dict

class harmonia.mapper.map_transform.CartesianMap(catalogues, orders, kmin=None, kmax=None, dk=None, num_mesh=256, resampler='tsc', interlaced=True)[source]

Compressed Cartesian Fourier-space map from catalogue sources.

Parameters:

  • catalogues (SphericalFKPCatalogue or FKPCatalog) – FKP-style paired catalogues in a spherical domain.

  • orders (sequence of int) – Orders of the power spectrum multipoles.

  • kmin (float, optional) – Minimum wavenumber of the compressed map (in \(h\)/Mpc) (default is None).

  • kmax (float or None, optional) – Maximum wavenumber of the compressed map (in \(h\)/Mpc) (default is None).

  • dk (float or None, optional) – Wavenumber bin width (in \(h\)/Mpc) (default is None).

  • num_mesh (int, optional) – Mesh number per dimension for interpolating the discrete catalogues on a grid.

  • resampler ({‘cic’, ‘tsc’, ‘pcs’}, optional) – Grid assignment scheme (default is ‘tsc’) for catalogue interpolation.

  • interlaced (bool, optional) – If True (default), use interlacing for aliasing mitigation.

Variables: