The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

TL;DR

This study reveals a tight correlation between stellar and dynamical surface densities in the central regions of disk galaxies, with deviations indicating dark matter influence, using a large galaxy sample from the SPARC database.

Contribution

It establishes a detailed relation between stellar and dynamical densities across diverse galaxy types, highlighting the role of dark matter in low surface brightness galaxies.

Findings

High surface brightness galaxies are baryon dominated and follow a 1:1 relation.

Low surface brightness galaxies deviate from the 1:1 line, indicating increasing dark matter influence.

The relation is tight with small scatter (~0.2 dex), unaffected by other galaxy properties.

Abstract

We use the SPARC (Spitzer Photometry & Accurate Rotation Curves) database to study the relation between the central surface density of stars Sstar and dynamical mass Sdyn in 135 disk galaxies (S0 to dIrr). We find that Sdyn correlates tightly with Sstar over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.