Testing MONDian Dark Matter with Galactic Rotation Curves

TL;DR

This study tests MONDian dark matter (MDM) against galactic rotation curves, finding it fits observations as well as MOND and CDM, and reveals unique density profile features near galaxy centers.

Contribution

First observational test of MDM using galaxy rotation curves, demonstrating its compatibility with data and distinguishing it from MOND near galaxy centers.

Findings

MDM fits rotation curves as well as MOND and CDM.

MDM and MOND predictions are nearly indistinguishable over observed radii.

MDM density profile shows a turnover and decrease near galaxy centers.

Abstract

MONDian dark matter (MDM) is a new form of dark matter quantum that naturally accounts for Milgrom's scaling, usually associated with modified Newtonian dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at cluster and cosmic scales. In this paper, we provide the first observational test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies (z approximately 0.003). For comparison, we also fit the galactic rotation curves using MOND, and CDM. We find that all three models fit the data well. The rotation curves predicted by MDM and MOND are virtually indistinguishable over the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM density profiles are compared. We also compare with MDM the dark matter density profiles arising from MOND if Milgrom's formula is interpreted as Newtonian gravity with an extra source term instead of as a modification of inertia. We find that discrepancies between MDM and MOND will occur near the center of a typical spiral galaxy. In these regions, instead of continuing to rise sharply, the MDM mass density turns over and drops as we approach the center of the galaxy. Our results show that MDM, which restricts the nature of the dark matter quantum by accounting for Milgrom's scaling, accurately reproduces observed rotation curves.