Mock Catalogue Simulation

This module simulates a Stage IV-like weak lensing observation and generate mock galaxy shear catalogues. The catalogue simulation is executed by running run_cat_sim.sh in bash.

To set up the simulation we need to define the survey parameters in set_variables_cat.ini config file, and direct the pipeline path in run_cat_sim.sh. The simulated catalogues will be saved on disk in a location specified in the config file. The config file contains detailed information on setup parameters, but to note specifically, in set_variables_cat.ini:

• Change the PIPELINE_DIR to the root directory where the package is installed, i.e.

PIPELINE_DIR=/path-in-system/SWEPT/

• Change the redshift distribution parameters in redshift_distribution. Here ZMIN, ZMAX, DZ are the minimum redshift, maximum redshift, and resolution to characterise the n(z) redshift distribution for the sample. The parameters Z0, BETA describe the functional form of the n(z) distribution (see also Eq. 44 in Wong+24). Finally, NGAL is the number of galaxies to include in the mock sample, expressed in scientific form, i.e. ‘1e6’ for 1m galaxies.

• In [create_nz], NZ_TABLE_NAME does not need to be changed. However, we need to specify the number of bins in redshift space to use to generate maps at. Generally, we want the number of bins to match the number of sample points, i.e. N_ZBIN=(ZMAX-ZMIN)/DZ. We recommend that for a full 3x2pt analysis you used DZ``=0.1. However,  if the number of sample points exceeds the number of points at which we generate maps to sample the redshift distribution, the code will interpolate field values per pixel, to 'fill in' the missing information in redshift. We recommend that no interpolation should be used for a full 3x2pt cosmological analysis, as the interpolation can introduce correlations that may contaminate precision cosmological constraints. For shear-only, you can get away with using a smaller ``DZ, but the number of bins may not be able to match the number of sample points (e.g. due to numerical errors if fields in each bin) are generated very close together. In this shear only case, the effects of interpolation will not be as significant as a full 3x2pt analysis (since the shear signal is reasonably well described by a cumulative sum/interpolation along the line of sight)

• In simulation set up, change the SIMULATION_SAVE_DIR to the path where you want the catalogues to be saved. Also change the NSIDE, ELL range, and number of REALISATIONS as required. The mock observation will be generated over a given survey mask. This mask must be saved, in HEALPIX format on your local machine. The PATH_TO_MASK is the path to where your survey mask is saved on disk. Note that the NSIDE of the mask must match the NSIDE specified in the parameter space otherwise the code will have unexpected behaviour!

• In [compile_cat], change the errors injected into the redshift photo-z estimates and galaxy/shear shapes.

• Change the COSMOSIS_ROOT_DIR to the directory where CosmoSIS is installed on disk.

And in run_cat_sim.sh, change the PIPELINE_VARIABLES_PATH to the path where the set_variables_cat.ini file is located, i.e. PIPELINE_VARIABLES_PATH=/path-in-system/SWEPT/catalogue_sim/set_variables_cat.ini

• clean_products script
• compile_cat module
  • compile_cat_config()
  • execute_cat_compilation()
  • generate_cat_err_sig()
  • split_z_chunks()
• conv_fields_cosmosis_flask module
  • conversion_config()
  • execute()
  • main()
  • normalise_power()
  • open_data()
• create_nz module
  • create_nz()
  • create_zbin_boundaries()
  • main()
  • nz_config()
• init_rand_sample module
  • init_nz()
  • main()
  • pz()
  • pz_config()
• interp_maps module
  • execute_interpolation()
  • interp_config()
  • load_map_slices()
  • main()
  • save_interp_map()
  • setup_interpolation()
• poisson_sample_gal_position module
  • execute_poisson_sampling()
  • poisson_sample_masked_map()
• run_cat_sim bash script
• run_flask module
  • flask_config()
  • main()
• set_variables_cat config setup