Dark Energy Survey Year 3 results: Galaxy-halo connection from galaxy-galaxy lensing

TL;DR

This paper analyzes the galaxy-halo connection using galaxy-galaxy lensing data from DES Year 3, extending measurements to small scales and improving constraints on halo masses, galaxy bias, and satellite fractions for different galaxy samples.

Contribution

It introduces an extended galaxy-galaxy lensing measurement on nonlinear scales and refines constraints on galaxy-halo properties, enhancing understanding of galaxy evolution and cosmology.

Findings

Halo masses are approximately constant over redshift for both galaxy samples.

Constraints on halo masses are improved by about 15% over previous work.

Galaxy bias is constrained more than five times better than large-scale only estimates.

Abstract

Galaxy-galaxy lensing is a powerful probe of the connection between galaxies and their host dark matter halos, which is important both for galaxy evolution and cosmology. We extend the measurement and modeling of the galaxy-galaxy lensing signal in the recent Dark Energy Survey Year 3 cosmology analysis to the highly nonlinear scales ($\sim 100$ kpc). This extension enables us to study the galaxy-halo connection via a Halo Occupation Distribution (HOD) framework for the two lens samples used in the cosmology analysis: a luminous red galaxy sample (redMaGiC) and a magnitude-limited galaxy sample (MagLim). We find that redMaGiC (MagLim) galaxies typically live in dark matter halos of mass $\log_{10}(M_{h}/M_{\odot}) \approx 13.7$ which is roughly constant over redshift ($13.3-13.5$ depending on redshift). We constrain these masses to $\sim 15\%$, approximately $1.5$ times improvement over previous work. We also constrain the linear galaxy bias more than 5 times better than what is inferred by the cosmological scales only. We find the satellite fraction for redMaGiC (MagLim) to be $\sim 0.1-0.2$ ($0.1-0.3$) with no clear trend in redshift. Our constraints on these halo properties are broadly consistent with other available estimates from previous work, large-scale constraints and simulations. The framework built in this paper will be used for future HOD studies with other galaxy samples and extensions for cosmological analyses.