CosmoDC2 python package

This python package generates the cosmoDC2 synthetic galaxy catalog used by LSST-DESC for Data Challenge 2.

Code Overview

Here we provide the locations of the most important functions used to generate the cosmoDC2 synthetic galaxy catalog. Undocumented modules and notebooks are not intended to provide user-facing functionality.

Mock production scripts

The scripts driving the generation of the cosmoDC2 catalog are contained in the cosmodc2/scripts directory. In particular:

• run_cosmoDC2_healpix_production.pyproduces the synthetic lightcones. This script primarily functions as a wrapper around the write_umachine_healpix_mock_to_disk.py module in the top-level of the package.
• run_cosmoDC2_snapshot_production.py produces synthetic catalogs at a single redshift. This script primarily functions as a wrapper around the write_umachine_snapshot_mock_to_disk.py module in the top-level of the package.

Models for the galaxy-halo connection

Stellar mass

Code implementing the model used in cosmoDC2 for stellar mass is located in the stellar_mass_remapping directory. The primary callable of interest is the remap_stellar_mass_in_snapshot function defined in the remap_high_mass_smhm.py module.

Restframe optical color

Code implementing the model used in cosmoDC2 for broadband optical color is located in the sdss_colors directory. The primary callable of interest is the assign_restframe_sdss_gri function defined in the v4_sdss_assign_gri.py module.

Black holes

Code implementing the model used in cosmoDC2 for black hole mass and accretion rate is located in the black_hole_modeling directory. The primary callables of interest are:

• The monte_carlo_black_hole_mass function models black hole mass and is located in the black_hole_mass.py module.
• The monte_carlo_bh_acc_rate function models black hole accretion rate and is located in the black_hole_accretion_rate.py module.

Sizes

Code implementing the model used in cosmoDC2 to map half-light radii onto the galaxy's bulge and disk component is located in the size_modeling directory. The primary callables of interest are the mc_size_vs_luminosity_early_type function and the mc_size_vs_luminosity_late_type function in the zhang_yang17.py module.

Ultra-faint population

Code implementing the model used in cosmoDC2 to extend the resolution limits of the Outer Rim simulation to capture the ultra-faint galaxy population is located in the synthetic_subhalos directory. The primary callables of interest are:

• The model_extended_mpeak function located in the extend_subhalo_mpeak_range.py module.
• The create_synthetic_lowmass_mock_with_centrals function located in the extend_subhalo_mpeak_range.py module.

Code versions

The following git tags can be used to check out various versions of the code:

• v1.1.4 - This version of the code generated the ~440 deg**2 extragalactic catalog for the DC2 image simulation.