Quantifying the power spectrum of small-scale structure in semi-analytic galaxies

TL;DR

This paper analyzes the small-scale structure in simulated galaxies' dark matter distribution using power spectrum analysis, aiming to differentiate between cold and warm dark matter models through gravitational lensing observations.

Contribution

It introduces a method to quantify the power spectrum of small-scale structures in simulated galaxies, providing a basis for testing dark matter models with lensing data.

Findings

Power spectrum slope and amplitude can distinguish CDM from warm dark matter.

Measurement of the power spectrum on galaxy lensing scales is feasible.

Detection of massive subhalos enhances model discrimination.

Abstract

In the cold dark matter (CDM) picture of structure formation, galaxy mass distributions are predicted to have a considerable amount of structure on small scales. Strong gravitational lensing has proven to be a useful tool for studying this small-scale structure. Much of the attention has been given to detecting individual dark matter subhalos through lens modeling, but recent work has suggested that the full population of subhalos could be probed using a power spectrum analysis. In this paper we quantify the power spectrum of small-scale structure in simulated galaxies, with the goal of understanding theoretical predictions and setting the stage for using measurements of the power spectrum to test dark matter models. We use a sample of simulated galaxies generated from the \texttt{Galacticus} semi-analytic model to determine the power spectrum distribution first in the CDM paradigm and then in a warm dark matter scenario. We find that a measurement of the slope and amplitude of the power spectrum on galaxy strong lensing scales ($k\sim 1$ kpc$^{-1}$) could be used to distinguish between CDM and alternate dark matter models, especially if the most massive subhalos can be directly detected via gravitational imaging.