[Paper Review] Newtonian explanation of galaxy rotation curves based on distribution of baryonic matter

Konstantin Pavlovich, Alex Pavlovich+1 more|arXiv (Cornell University)|Jun 10, 2014

Galaxies: Formation, Evolution, Phenomena16 references3 citations

TL;DR

This paper proposes that galaxy rotation curves can be fully explained by Newtonian gravity using only the distribution of baryonic matter, without requiring dark matter or modified gravity. By modeling realistic mass distributions, the authors show that rotation curves are naturally flat or rising, achieving a correlation >0.995 between predicted and observed velocities across 47 galaxies.

ABSTRACT

Circular velocities of stars and gas in galaxies generally do not decline in accordance with widely expected Keplerian fall-off in velocities further from the galactic nucleus. Two main groups of theories were proposed to explain the supposed discrepancy--first, the most commonly accepted, is the suggestion of the existence of large non-baryonic dark matter halo, and, second are theories advocating some modification to the law of gravity. So far however, there is no empirical evidence for either dark matter or modified gravity. Here we show that a broad range of galaxy rotation curves can be explained solely in accordance with Newton's law of gravity by modeling the distribution of baryonic matter in a galaxy. We demonstrate that the expectation of Keplerian fall-off is incorrect, and that a large number of likely galaxy mass distribution profiles should in fact produce flat or accelerating rotation curves similar to those observed in reality. We further support our theoretical findings with the model fit of 47 rotation curves of real galaxies, representing a broad range of galactic types and sizes, and achieving correlation of expected and observed velocities of over 0.995 for all cases. Our results make theories of exotic dark matter or modified gravity unnecessary for the explanation of galaxy rotation curves.

Motivation & Objective

• To challenge the widely accepted need for dark matter or modified gravity in explaining flat galaxy rotation curves.
• To investigate whether Newtonian gravity applied to baryonic mass distributions can reproduce observed rotation curves.
• To test if the assumption of Keplerian velocity decline is incorrect for realistic galactic mass profiles.
• To provide a unified explanation for diverse galaxy types using only baryonic matter and standard gravity.
• To demonstrate that observed rotation curves are consistent with Newtonian dynamics when proper mass distributions are modeled.

Proposed method

• Modeling galactic mass distributions using realistic, non-uniform baryonic matter profiles derived from observed luminosity and density distributions.
• Applying Newton's law of universal gravitation to compute circular velocities at various radii from the galactic center.
• Using analytical and numerical integration to compute gravitational potential and orbital velocities from the mass distribution.
• Fitting the model to observed rotation curves of 47 galaxies across different morphological types and sizes.
• Comparing predicted rotation velocities with observed data using correlation coefficients to assess model accuracy.
• Analyzing the shape of rotation curves under different mass distribution assumptions to show non-Keplerian behavior is expected.

Experimental results

Research questions

• RQ1 Can Newtonian gravity alone explain the flat or rising rotation curves of galaxies without invoking dark matter?
• RQ2 Is the assumption of Keplerian velocity decline valid for realistic galactic mass distributions?
• RQ3 What is the degree of agreement between predicted and observed rotation velocities when only baryonic matter is considered?
• RQ4 Do different galaxy types (e.g., spiral, dwarf) require different mass distribution models to reproduce their rotation curves?
• RQ5 Can a single Newtonian framework with baryonic matter account for the full range of observed rotation curve shapes?

Key findings

• A broad range of realistic baryonic mass distributions produce flat or accelerating rotation curves, contradicting the expectation of Keplerian decline.
• The model achieves a correlation of over 0.995 between predicted and observed rotation velocities across 47 galaxies of diverse types and sizes.
• The observed rotation curves are consistent with Newtonian gravity when the full three-dimensional distribution of baryonic matter is properly accounted for.
• The need for non-baryonic dark matter or modifications to gravity is not supported by the data when proper mass modeling is applied.
• Theoretical analysis shows that the Keplerian fall-off is an oversimplification that does not hold for extended, non-uniform mass distributions.
• The results demonstrate that the observed rotation curve behavior is a natural consequence of Newtonian dynamics applied to realistic galactic mass profiles.