Investigating the Redshift Evolution of Lensing Galaxy Density Slopes via Model-Independent Distance Ratios

TL;DR

This study introduces a model-independent method using artificial neural networks to analyze the redshift evolution of galaxy density slopes in strong lensing systems, providing insights into galaxy evolution and cosmology.

Contribution

The paper presents a novel, dark energy-model-independent approach employing ANNs and an extended power-law model to study the evolution of lensing galaxy density slopes.

Findings

Negative trend in density slope with redshift ($eta = -0.20 \

Robust estimates achieved through multi-level analysis.

Forecasts suggest high precision in constraining slope evolution with upcoming surveys.

Abstract

Strong lensing systems, expected to be abundantly discovered by next-generation surveys, offer a powerful tool for studying cosmology and galaxy evolution. The connection between galaxy structure and cosmology through distance ratios highlights the need to examine the evolution of lensing galaxy mass density profiles. We propose a novel, dark energy-model-independent method to investigate the mass density slopes of lensing galaxies and their redshift evolution using an extended power-law (EPL) model. We employ a non-parametric approach based on Artificial Neural Networks (ANNs) trained on Type Ia Supernovae (SNIa) data to reconstruct distance ratios of strong lensing systems. These ratios are compared with theoretical predictions to estimate the evolution of EPL model parameters. Analyses conducted at three levels, including the combined sample, individual lenses, and binned groups, ensure robust and reliable estimates. A negative trend in the mass density slope with redshift is observed, quantified as $\partial\gamma/\partial z = -0.20 \pm 0.12$ under a triangular prior for anisotropy. This study demonstrates that the redshift evolution of density slopes in lensing galaxies can be determined independently of dark energy models. Simulations based on LSST Rubin Observatory forecasts, which anticipate 100,000 strong lenses, show that spectroscopic follow-up of just 10 percent of these systems can constrain the redshift evolution coefficient with uncertainty ($\Delta\partial\gamma/\partial z$) to 0.021. This precision distinguishes evolving and non-evolving density slopes, providing new insights into galaxy evolution and cosmology.