2021MNRAS.503.4147P

We present a new suite of mock galaxy catalogues mimicking the low-redshift Universe, based on an updated halo occupation distribution (HOD) model and a scaling relation between optical properties and the neutral hydrogen (H I) content of galaxies. Our algorithm is constrained by observations of the luminosity function and luminosity- and colour-dependent clustering of Sloan Digital Sky Survey (SDSS) galaxies, as well as the H I mass function and H I-dependent clustering of massive H I-selected galaxies in the Arecibo Legacy Fast ALFA (ALFALFA) survey. Mock central and satellite galaxies with realistic values of r-band luminosity, g - r and u - r colour, stellar mass and H I mass are populated in an N-body simulation, inheriting a number of properties of the density and tidal environment of their host haloes. The host halo of each central galaxy is also 'baryonified' with realistic spatial distributions of stars as well as hot and cold gas, along with the corresponding rotation curve. Our default HOD assumes that galaxy properties are a function of group halo mass alone, and can optionally include effects such as galactic conformity and colour-dependent galaxy assembly bias. The mocks predict the relation between the stellar mass and H I mass of massive H I galaxies, as well as the 2-point cross-correlation function of spatially co-located optical and H I-selected samples. They enable novel null tests for galaxy assembly bias, provide predictions for the H I velocity width function, and clarify the origin and universality of the radial acceleration relation in the Lambda cold dark matter framework.