Galaxy rotation curves with log-normal density distribution

TL;DR

This paper proposes a log-normal density distribution model for galactic disks that fits observed rotation curves without invoking dark matter or MOND, suggesting an alternative explanation for galaxy dynamics.

Contribution

The study introduces a modified log-normal density distribution model that accurately fits galaxy rotation curves, challenging dark matter halo assumptions.

Findings

Model fits 37 galaxy rotation curves across different types.

Total disk masses align with the baryonic Tully-Fisher relation.

Suggests mass distribution confined to a thin plane without dark matter.

Abstract

The log-normal distribution represents the probability of finding randomly distributed particles in a micro canonical ensemble with high entropy. To a first approximation, a modified form of this distribution with a truncated termination may represent an isolated galactic disk, and this disk density distribution model was therefore run to give the best fit to the observational rotation curves for 37 representative galaxies. The resultant curves closely matched the observational data for a wide range of velocity profiles and galaxy types with rising, flat or descending curves in agreement with Verheijen's classification of 'R', 'F' and 'D' type curves, and the corresponding theoretical total disk masses could be fitted to a baryonic Tully Fisher relation (bTFR). Nine of the galaxies were matched to galaxies with previously published masses, suggesting a mean excess dynamic disk mass of dex0.61+/-0.26 over the baryonic masses. Although questionable with regard to other measurements of the shape of disk galaxy gravitational potentials, this model can accommodate a scenario in which the gravitational mass distribution, as measured via the rotation curve, is confined to a thin plane without requiring a dark-matter halo or the use of MOND.