GGCorrelation: Shear-Shear Correlations

The GGCorrelation class computes the two-point correlation of spin-2 fields.

Example

import orpheus

cat = orpheus.SpinTracerCatalog(
    spin=2, pos1=x, pos2=y, tracer_1=g1, tracer_2=g2)
gg = orpheus.GGCorrelation(
    min_sep=1., max_sep=128., binsize=0.1, nthreads=nthreads)
gg.process(cat)      # Compute 2pcf
class orpheus.GGCorrelation(min_sep, max_sep, **kwargs)[source]

Bases: BinnedNPCF

Compute second-order correlation functions of spin-2 fields.

Parameters

  • min_sep (float) – The smallest distance of each vertex for which the NPCF is computed.

  • max_sep (float) – The largest distance of each vertex for which the NPCF is computed.

xip

The ξ₊ correlation function.

Type

numpy.ndarray

xim

The ξ₋ correlation function.

Type

numpy.ndarray

norm

The number of weighted pairs.

Type

numpy.ndarray

npair

The number of unweighted pairs.

Type

numpy.ndarray

Notes

Inherits all other parameters and attributes from BinnedNPCF. Additional child-specific parameters can be passed via kwargs. Either nbinsr or binsize has to be provided to fix the binning scheme.

saveinst(path_save, fname)[source]
__process_patches(cat, dotomo=True, do_dc=False, rotsignflip=False, apply_edge_correction=False, adjust_tree=False, save_patchres=False, save_filebase='', keep_patchres=False)
process(cat, dotomo=True, do_dc=False, rotsignflip=False, adjust_tree=False, save_patchres=False, save_filebase='', keep_patchres=False)[source]

Compute a shear 2PCF given a shape catalog

Parameters

  • cat (orpheus.SpinTracerCatalog) – The shape catalog to process.

  • dotomo (bool) – Flag that decides whether the tomographic information in the shape catalog should be used. Defaults to True.

  • do_dc (bool) – Whether to double-count pair counts. This will have no impact on \(\xi_\pm\), but can significantly reduce the amplitude of \(\xi_\times\). Defaults to False.

  • rotsignflip (bool) – If the shape catalog has been decomposed in patches, choose whether the rotation angle should be flipped. For simulated data this was always ok to set to False. Defaults to False.

  • adjust_tree (bool) – Overrides the original setup of the tree-approximations in the instance based on the nbar of the shape catalog. Not implemented yet; has no effect. Defaults to False.

  • save_patchres (bool or str) – If the shape catalog has been decomposed in patches, flag whether to save the GG measurements on the individual patches. Note that the path needs to exist, otherwise a ValueError is raised. For a flat-sky catalog this parameter has no effect. Defaults to False.

  • save_filebase (str) – Base of the filenames in which the patches are saved. The full filename will be <save_patchres>/<save_filebase>_patchxx.npz. Only has an effect if the shape catalog consists of multiple patches and save_patchres is not False.

  • keep_patchres (bool) – If the catalog consists of multiple patches, returns all measurements on the patches. Defaults to False.

computeMap2(radii, tofile=False)[source]

Computes second-order aperture mass statistics given the shear correlation functions. Uses the Crittenden 2002 filter.

_checkcats(cats, spins)
_initprojections(child)
_print_npcfprojections_avail(child)
_projectnpcf(child, projection)

Projects npcf to a new basis.

_updatetree(new_resos, include_shifts=True)
autoset_tree(cat, dpix_grid=2.0, nside_grid=2048)