ADDGALS: Simulated Sky Catalogs for Wide Field Galaxy Surveys

Abstract

We present a method for creating simulated galaxy catalogs with realistic galaxy luminosities, broad-band colors, and projected clustering over large cosmic volumes. The technique, denoted ADDGALS (Adding Density Dependent GAlaxies to Lightcone Simulations), uses an empirical approach to place galaxies within lightcone outputs of cosmological simulations. It can be applied to significantly lower-resolution simulations than those required for commonly used methods such as halo occupation distributions, subhalo abundance matching, and semi-analytic models, while still accurately reproducing projected galaxy clustering statistics down to scales of r ∼ 100 h −1 kpc . We show that ADDGALS catalogs reproduce several statistical properties of the galaxy distribution as measured by the Sloan Digital Sky Survey (SDSS) main galaxy sample, including galaxy number densities, observed magnitude and color distributions, as well as luminosity-and color-dependent clustering. We also compare to cluster-galaxy cross correlations, where we find significant discrepancies with measurements from SDSS that are likely linked to artificial subhalo disruption in the simulations. Applications of this model to simulations of deep wide-area photometric surveys, including modeling weak-lensing statistics, photometric redshifts, and galaxy cluster finding are presented in DeRose et al. (2019a), and an application to a full cosmology analysis of Dark Energy Survey (DES) Year 3 like data is presented in DeRose et al. (2021a). We plan to publicly release a 10,313 square degree catalog constructed using ADDGALS with magnitudes appropriate for several existing and planned surveys, including SDSS, DES, VISTA, WISE, and LSST.

Superclustering with the Atacama Cosmology Telescope and Dark Energy Survey: I. Evidence for thermal energy anisotropy using oriented stacking

“…In Buzzard, the number of identified redMaPPer clusters is a factor of 3-5 below the number of real redMaPPer clusters for the redshifts and richnesses used in our work. This deficit is likely due to a reduced number of galaxies in the central regions of galaxy clusters and a reduced number of red galaxies in dense regions, both of which result in fewer richness selected clusters (D19, Wechsler et al 2021). Despite the lower cluster number density, the number of Buzzard clusters available to use for this work is ∼ 5 times larger than it is for DES.…”

“…The Buzzard galaxy and cluster catalogs were explicitly designed to provide a comparison with DES by replicating many of the survey's selection effects; therefore this simulation suite is the most straightforward choice for direct comparison with our ACT×DES results. Buzzard assigns realistic galaxies to dark matter halos in N -body dark-matter only simulations using the ADDGALS method (Wechsler et al 2021). The implemented cosmology has Ω m = 0.286, h = 0.7, σ 8 = 0.82.…”

The scatter in the galaxy-halo connection: a machine learning analysis

“…The former is useful for making mock universes from cheap DM-only simulations-which can then be used either for forecasting upcoming cosmological galaxy surveys (e.g. Reddick et al 2014;Zhang et al 2019;Kasmanoff et al 2020;Wechsler et al 2021) or for validating and developing analysis pipelines for these surveys (e.g. DeRose et al 2019)-while the latter is useful for estimating the distribution of DM associated with the observed distribution of light.…”

Galaxy blending effects in deep imaging cosmic shear probes of cosmology

“…Buzzard is a set of synthetic galaxy catalogues tuned for the Dark Energy Survey (DES) but applicable to a variety of large-area photometric and spectroscopic surveys. The simulation employs a set of dark matter-only simulations and then utilizes the ADDGALS algorithm (Wechsler et al 2021) to paint baryonic galaxies on these dark matter simulations. This simulation is constructed from a set of three dark matter N-body simulations run using L-GADGET2, a modified version of GADGET2 7 with box lengths ranging from 1-4 ℎ −1 Gpc from which light-cones were constructed.…”