Investigating the Correlation between Dark Matter Content, Ages and Mass-to-Light Ratios in Spiral Galaxies

TL;DR

This study empirically links galactic age with dark matter content, mass-to-light ratios, and density in spiral galaxies, supporting theories of dark matter assembly over cosmic time.

Contribution

It provides observational evidence connecting galaxy age to dark matter accumulation, using detailed rotation curve modeling and extensive literature data.

Findings

Strong positive correlation between galaxy age and dark matter mass

Significant relationship between age and mass-to-light ratios

Results align with cosmological simulations of dark matter assembly

Abstract

We present an empirical investigation into the relationship between galactic age and dark matter content across a sample of 16 nearby, well-resolved spiral galaxies. Using raw rotation curve data from IOA Tokyo's publicly available repository, we model each galaxy's mass distribution via a three-component decomposition (Hernquist bulge, exponential disk, and a Navarro-Frenk-White (NFW) dark matter halo) fit using Monte Carlo simulations. The onset of dark matter dominance was identified using the NFW scale radius, beyond which we computed the total enclosed mass via Keplerian dynamics. I-band luminosities for these regions were estimated using a calibrated Tully-Fisher relation, yielding precise mass-to-light (M/L) ratios. We further calculated dark matter mass and density using NFW profile equations, and galaxy ages were retrieved through an extensive literature survey of stellar population studies. Our analysis reveals strong positive correlations between galactic age and both dark matter mass (Pearson $r \approx 0.91$; Spearman $\rho \approx 0.93$) and density (Pearson $r \approx 0.91$; Spearman $\rho \approx 0.91$), as well as M/L ratios, suggesting a robust link between evolutionary history and dark matter build-up. These findings are in quantitative agreement with predictions from large-scale cosmological simulations that incorporate assembly bias and smooth accretion-dominated growth, reinforcing the view that older galaxies, having formed earlier in high-density peaks, have accumulated significantly more dark matter over cosmic time. Our results offer observational evidence for time-dependent dark matter assembly and establish galactic age as a meaningful tracer of halo evolution.