Next Article in Journal
Nonlocal General Relativity
Next Article in Special Issue
The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications
Previous Article in Journal / Special Issue
Astrophysical Tests of Kinematical Conformal Cosmology in Fourth-Order Conformal Weyl Gravity
Article Menu

Export Article

Open AccessReview
Galaxies 2014, 2(4), 601-622;

The Third Law of Galactic Rotation

Department of Astronomy, Case Western Reserve University, Cleveland, OH 44118, USA
Received: 6 October 2014 / Revised: 27 November 2014 / Accepted: 11 December 2014 / Published: 17 December 2014
(This article belongs to the Special Issue Beyond Standard Gravity and Cosmology)
Full-Text   |   PDF [899 KB, uploaded 17 December 2014]   |  


I review the connection between dynamics and the baryonic mass distribution in rotationally-supported galaxies. The enclosed dynamical mass-to-light ratio increases with decreasing galaxy luminosity and surface brightness. The correlation with surface brightness appears to be the more fundamental, with the dependence on luminosity following simply from the weaker correlation between luminosity and surface brightness. In addition to this global relation, there is also a local relation between the amplitude of the mass discrepancy and the acceleration predicted by the observed distribution of baryons. I provide an empirical calibration of this mass discrepancy-acceleration relation. The data are consistent with the operation of a singe effective force law in disk galaxies, making this relation tantamount to a natural law. I further provide formulae by which the radial dark matter distribution can be estimated from surface photometry. The form of the dark matter halo depends uniquely on the distribution of baryons in each galaxy and, in general, is neither a cusp nor a core. It remains difficult to see how galaxy formation models can reproduce the observed behavior, which is uniquely predicted by MOND. View Full-Text
Keywords: dark matter; galaxies: formation; galaxies: kinematics and dynamics; galaxies: structure dark matter; galaxies: formation; galaxies: kinematics and dynamics; galaxies: structure

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

McGaugh, S.S. The Third Law of Galactic Rotation. Galaxies 2014, 2, 601-622.

Show more citation formats Show less citations formats

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Galaxies EISSN 2075-4434 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top