Rosella: A mock catalogue from the P-Millennium simulation

TL;DR

This paper presents a high-fidelity mock galaxy catalogue based on the P-Millennium simulation, designed to closely mimic DESI BGS galaxy properties for survey analysis and systematics testing.

Contribution

It introduces a detailed mock catalogue using subhalo abundance matching with scatter, incorporating galaxy colors, magnitudes, and host halo information at the DESI BGS redshift.

Findings

Provides a complete galaxy sample with positions, velocities, and properties.

Enables testing of analysis pipelines and systematic effects.

Supports interpretation of DESI BGS data.

Abstract

The scientific exploitation of the Dark Energy Spectroscopic Instrument Bright Galaxy Survey (DESI BGS) data requires the construction of mocks with galaxy population properties closely mimicking those of the actual DESI BGS targets. We create a high fidelity mock galaxy catalogue, including information about galaxies and their host dark matter subhaloes. The mock catalogue uses subhalo abundance matching (SHAM) with scatter to populate the P-Millennium N-body simulation with galaxies at the median BGS redshift of ~ 0.2, using formation redshift information to assign (g-r) rest-frame colours. The mock provides information about r-band absolute magnitudes, (g-r) rest-frame colours, 3D positions and velocities of a complete sample of DESI BGS galaxies in a volume of (542 Mpc/h)^3, as well as the masses of host dark matter haloes. This P-Millennium DESI BGS mock catalogue is ideally suited for the tuning of approximate mocks unable to resolve subhaloes that DESI BGS galaxies reside in, to test for systematics in analysis pipelines and to interpret (non-cosmological focused) DESI BGS analysis.