The (dark) halo-to-stellar mass ratio in the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G)

TL;DR

This study estimates the halo-to-stellar mass ratio in 1154 disk galaxies using infrared photometry and rotation curves, finding consistency with cosmological models and revealing a constant fraction of dark matter within the optical disk.

Contribution

It provides the first large-scale empirical measurement of the halo-to-stellar mass ratio within the optical disks of galaxies, aligning observations with ΛCDM simulations.

Findings

The halo-to-stellar mass ratio correlates with stellar mass.

Within the optical disk, dark matter constitutes about 4% of the total halo mass.

Results agree with ΛCDM model predictions at z≈0.

Abstract

We use 3.6 $\mu$m photometry for 1154 disk galaxies ($i<65^{\circ}$) in the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G, Sheth et al. 2010) to obtain the stellar component of the circular velocity. By combining the disk+bulge rotation curves with HI line width measurements from the literature, we estimate the ratio of the halo-to-stellar mass ($M_{\rm halo}/M_{\ast}$) within the optical disk, and compare it to the total stellar mass ($M_{\ast}$). We find the $M_{\rm halo}/M_{\ast}$-$M_{\ast}$ relation in good agreement with the best-fit model at z$\approx$0 in $\Lambda$CDM cosmological simulations (e.g. Moster et al. 2010), assuming that the dark matter halo within the optical radius comprises a constant fraction ($\sim4\%$) of its total mass.