Investigating Dark Matter and MOND Models with Galactic Rotation Curve Data: Analysing the Gas-Dominated Galaxies

TL;DR

This study analyzes gas-dominated galaxies in the SPARC database within a normalized acceleration space to understand their geometry, providing insights into dark matter and MOND models while reducing uncertainties and mass-to-light ratio effects.

Contribution

It introduces a normalized $g2$-space analysis of gas-dominated galaxies, revealing their geometry and implications for dark matter and modified gravity theories.

Findings

Gas-dominated galaxies exhibit a rightward curving geometry in normalized $g2$-space.

Overall galaxy geometry in SPARC is nearly linear with a slight rightward curvature.

Geometry differences suggest radial dependence of disk mass-to-light ratio.

Abstract

In this study the geometry of gas dominated galaxies in the SPARC database is analyzed in a normalized $(g_{bar},g_{obs})$-space ($g2$-space), where $g_{obs}$ is the observed centripetal acceleration and $g_{bar}$ is the centripetal acceleration as obtained from the observed baryonic matter via Newtonian dynamics. The normalization of $g2$-space significantly reduce the effect of both random and systematic uncertainties as well as enable a comparison of the geometries of different galaxies. Analyzing the gas-dominated galaxies (as opposed to other galaxies) further suppress the impact of the mass to light ratios. It is found that the overall geometry of the gas dominated galaxies in SPARC is consistent with a rightward curving geometry in the normalized $g2$-space (characterized by $r_{obs}>r_{bar}$, where $r_{bar}=\arg \max_r[g_{bar}(r)]$ and $r_{obs}=\arg \max_r[g_{obs}(r)]$). This is in contrast to the overall geometry of all galaxies in SPARC which best approximates a geometry curing nowhere in normalized $g2$-space (characterized by $r_{obs}=r_{bar}$) with a slight inclination toward a rightward curving geometry. The geometry of the gas dominated galaxies not only indicate the true (independent of mass to light ratios to leading order) geometry of data in $g2$-space (which can be used to infer properties on the solution to the missing mass problem) but also - when compared to the geometry of all galaxies - indicate the underlying radial dependence of the disk mass to light ratio.