Constraining cosmological parameters using density split lensing and the conditional stellar mass function

TL;DR

This work develops a simulation-based framework to constrain cosmological parameters via density split lensing (DSL) and the conditional stellar mass function (CSMF) HOD. By leveraging AbacusSummit N-body simulations and a CosmoPower emulator, the authors predict the excess surface mass density $ΔΣ(r_p)$ and the stellar mass function (SMF) across cosmologies, enabling a fast, environment-aware analysis for DESI and UNIONS. Key contributions include a detailed 11-parameter CSMF-HOD plus assembly-bias model, a covariance strategy combining Takahashi2017 mocks with emulator uncertainties, and a forecast showing Galaxy-DSL markedly improves constraints on $\sigma_8$ and $S_8$, especially when combined with all statistics. The framework demonstrates the practicality and impact of using environment-dependent lensing signals as cosmological probes for upcoming large surveys, providing a scalable path to jointly exploit spectroscopic and weak-lensing data.

Abstract

In this work, we develop a simulation-based model to predict the excess surface mass density (ESD) depending on the local density environment. Using a conditional stellar mass function, our foreground galaxies are tailored toward the bright galaxy sample of the early data release of the Dark Energy Spectroscopic Instrument (DESI). Due to the nature of the ESD measurement, our derived model is directly applicable to all DESI data. To build this model, we use the $\texttt{AbacusSummit}$ N-body simulation suite from which we measure all necessary statistics and train an emulator based on $\texttt{CosmoPower}$. Finally, we present a cosmological parameter forecast for a possible combined analysis of DESI and the Ultraviolet Near Infrared Optical Northern Survey.

Figures (16)

• Figure 1: Color versus stellar mass diagram. The solid line cuts right through the green valley, separating red and blue galaxies. To avoid interlopes, we shifted the cut criteria slightly upwards.
• Figure 2: Parameter distribution of all available AbacusSummit cosmologies.
• Figure 3: Dependence of the expectation value on the environment-based secondary bias parameters. In the upper panel, we show the dependence if we use the standard HOD description used, for instance, for luminous red galaxies Burger2024b. The lower panel shows that the modifications of the CSMF HOD described in this work result in similar effects.
• Figure 4: Stellar mass vs. spectroscopic distribution. The solid black line shows the derived stellar mass limit. The sample on the left side fulfills the stellar mass completeness criteria. The area enclosed by the red dashed line indicates the sample of galaxies used to build the model in Sect. \ref{['sec:summary_stat']}.
• Figure 5: SMF of the DESI-EDR described in Sect. \ref{['sec:prior']}, and the analytical predictions described in Sect. \ref{['sec:summary_stat']} for the first 200 points shown in Fig. \ref{['fig:paramerterspace_CSMF']}. The scaling by $1/0.8$ is explained in the main text due to possible incompleteness due to fibre magnitudes being too faint to measure redshifts.