Special Issue "Debate on the Physics of Galactic Rotation and the Existence of Dark Matter"

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (15 February 2020).

Special Issue Editors

Prof. Dr. Anne M. Hofmeister
E-Mail Website
Guest Editor
Department of Earth and Planetary Sciences, Washington University in Saint Louis, Louis, MO 63130, USA
Interests: heat transport; spectroscopy; classical physics; thermodynamics; inverse problems
Prof. Robert E. Criss
E-Mail Website
Guest Editor
Department of Earth and Planetary Sciences, Washington University in Saint Louis, Louis, MO 63130, USA
Interests: heat transport; spectroscopy; classical physics; thermodynamics; inverse problems

Special Issue Information

Dear Colleague,

We invite you to contribute to this Special Issue in Galaxies, the ‘’Debate on the Physics of Galactic Rotation and the Existence of Dark Matter.” Currently, two main philosophical camps exist. The main camp is based on models of Newtonian forces governing the orbits of stars, which requires copious amounts of dark matter to explain observed rotation curves. A competing view called MOND offered “modified Newtonian dynamics” to explain galactic rotation without dark matter. These ideas are irreconcilable and consensus does not exist. Consequently, a few additional individuals and small research groups have pursued Newtonian force models, disc models, and a spin model, all of which purportedly explain galactic rotation without invoking either dark matter or non-Newtonian forces.

This Issue has two goals. One is to provide a collection of brief reviews from prominent representatives of the above, diverse viewpoints that summarize their preferred model and provide cogent criticisms of other models. This effort will provide informed views on the strengths and weaknesses of competing models and foster both balance and communication between their various proponents. The second goal includes original papers on galactic rotation and is linked to dark matter, which may either diverge from the above approaches or offer new evidence not previously considered but which sheds light on the various possibilities. The overarching purpose is to stimulate discussion and/or provide alternative ideas, as a step towards an improved understanding.

Here is a video introduction of the Special Issue: https://wustl.app.box.com/s/tgquekywgtpcm5jawu99z78bmhfipnup

Prof. Dr. Anne M. Hofmeister
Prof. Robert E. Criss

Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • galactic rotation
  • dark matter
  • alternative models

Published Papers (10 papers)

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Editorial

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Open AccessEditorial
Debate on the Physics of Galactic Rotation and the Existence of Dark Matter
Galaxies 2020, 8(3), 54; https://doi.org/10.3390/galaxies8030054 - 15 Jul 2020
Viewed by 967
Abstract
This Special Issue was motivated by the disparate explanations of galactic dynamics promulgated by different philosophical camps [...] Full article

Research

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Open AccessArticle
Surface Brightness Plateau in S4G Galaxies
Galaxies 2020, 8(2), 48; https://doi.org/10.3390/galaxies8020048 - 06 Jun 2020
Cited by 1 | Viewed by 1698
Abstract
Using 3.6-μm data from 2112 galaxies, we show that, contrary to widely held expectations of a continuous steep decline, radial surface brightness profiles of galaxies tend to flatten and form extended plateaus beyond 27–28 magAB/arcsec2. This phenomenon could be [...] Read more.
Using 3.6-μm data from 2112 galaxies, we show that, contrary to widely held expectations of a continuous steep decline, radial surface brightness profiles of galaxies tend to flatten and form extended plateaus beyond 27–28 magAB/arcsec2. This phenomenon could be explained by the presence of extended stellar populations dominated by low-mass stars in galactic outskirts. The flattening of radial brightness profiles questions the artificial exponential extrapolations of brightness data and the automatic assumption that light always declines considerably faster than mass density, presenting an empirical challenge for the dark matter hypothesis. Full article
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Open AccessArticle
Gravitational Focusing of Low-Velocity Dark Matter on the Earth’s Surface
Galaxies 2020, 8(2), 42; https://doi.org/10.3390/galaxies8020042 - 16 May 2020
Cited by 2 | Viewed by 917
Abstract
We show that the Earth acts as a high-efficiency gravitational collector of low-velocity flow of dark matter (DM). The focal point appears on the Earth’s surface, when the DM flow speed is about 17 km/s with respect to the geo-center. We discuss diurnal [...] Read more.
We show that the Earth acts as a high-efficiency gravitational collector of low-velocity flow of dark matter (DM). The focal point appears on the Earth’s surface, when the DM flow speed is about 17 km/s with respect to the geo-center. We discuss diurnal modulation of the local DM density influenced by the Earth’s gravity. We also touch upon similar effects on galactic and solar system objects. Full article
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Open AccessArticle
Dark Matter Dogma: A Study of 214 Galaxies
Galaxies 2020, 8(2), 36; https://doi.org/10.3390/galaxies8020036 - 28 Apr 2020
Cited by 3 | Viewed by 3536
Abstract
The aim of this paper is to test the need for non-baryonic dark matter in the context of galactic rotation and the apparent difference between distributions of galactic mass and luminosity. We present a set of rotation curves and 3.6 μm surface brightness [...] Read more.
The aim of this paper is to test the need for non-baryonic dark matter in the context of galactic rotation and the apparent difference between distributions of galactic mass and luminosity. We present a set of rotation curves and 3.6 μm surface brightness profiles for a diverse sample of 214 galaxies. Using rotation curves as the sole input into our Newtonian disk model, we compute non-parametric radial profiles of surface mass density. All profiles exhibit lower density than parametric models with dark halos and provide a superior fit with observed rotation curves. Assuming all dynamical mass is in main-sequence stars, we estimate radial distributions of characteristic star mass implied by the corresponding pairs of density and brightness profiles. We find that for 132 galaxies or 62% of the sample, the relation between density and brightness can be fully explained by a radially declining stellar mass gradient. Such idealized stellar population fitting can also largely address density and brightness distributions of the remaining 82 galaxies, but their periphery shows, on average, 14 M/pc2 difference between total density and light-constrained stellar density. We discuss how this density gap can be interpreted, by considering a low-luminosity baryonic matter, observational uncertainties, and visibility cutoffs for red dwarf populations. Lastly, we report tight correlation between radial density and brightness trends, and the discovered flattening of surface brightness profiles—both being evidence against dark matter. Our findings make non-baryonic dark matter unnecessary in the context of galactic rotation. Full article
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Open AccessArticle
Density Profiles of 51 Galaxies from Parameter-Free Inverse Models of Their Measured Rotation Curves
Galaxies 2020, 8(1), 19; https://doi.org/10.3390/galaxies8010019 - 26 Feb 2020
Cited by 2 | Viewed by 803
Abstract
Spiral galaxies and their rotation curves have key characteristics of differentially spinning objects. Oblate spheroid shapes are a consequence of spin and reasonably describe galaxies, indicating that their matter is distributed in gravitationally interacting homeoidal shells. Here, previously published equations describing differentially spinning [...] Read more.
Spiral galaxies and their rotation curves have key characteristics of differentially spinning objects. Oblate spheroid shapes are a consequence of spin and reasonably describe galaxies, indicating that their matter is distributed in gravitationally interacting homeoidal shells. Here, previously published equations describing differentially spinning oblate spheroids with radially varying density are applied to 51 galaxies, mostly spirals. A constant volumetric density (ρ, kg m−3) is assumed for each thin homeoid in these formulae, after Newton, which is consistent with RCs being reported simply as a function of equatorial radius r. We construct parameter-free inverse models that uniquely specify mass inside any given r, and thus directly constrain ρ vs. r solely from velocity v (r) and galactic aspect ratios (assumed as 1:10 for spirals when data are unavailable). Except for their innermost zones, ρ is proven to be closely proportional to rn, where the statistical average of n for all 36 spirals studied is −1.80 ± 0.40. Our values for interior densities compare closely with independently measured baryon density in appropriate astronomical environments: for example, calculated ρ at galactic edges agrees with independently estimated ρ of intergalactic media (IGM). Our finding that central densities increase with galaxy size is consistent with behavior exhibited by diverse self-gravitating entities. Our calculated mass distributions are consistent with visible luminosity and require no non-baryonic component. Full article
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Open AccessArticle
Entropy and Mass Distribution in Disc Galaxies
Galaxies 2020, 8(1), 12; https://doi.org/10.3390/galaxies8010012 - 08 Feb 2020
Cited by 4 | Viewed by 766
Abstract
The relaxed motion of stars and gas in galactic discs is well approximated by a rotational velocity that is a function of radial position only, implying that individual components have lost any information about their prior states. Thermodynamically, such an equilibrium state is [...] Read more.
The relaxed motion of stars and gas in galactic discs is well approximated by a rotational velocity that is a function of radial position only, implying that individual components have lost any information about their prior states. Thermodynamically, such an equilibrium state is a microcanonical ensemble with maximum entropy, characterised by a lognormal probability distribution. Assuming this for the surface density distribution yields rotation curves that closely match observational data across a wide range of disc masses and galaxy types and provides a useful tool for modelling the theoretical density distribution in the disc. A universal disc spin parameter emerges from the model, giving a tight virial mass estimator with strong correlation between angular momentum and disc mass, suggesting a mechanism by which the proto-disc developed by dumping excess mass to the core or excess angular momentum to a satellite galaxy. The baryonic-to-dynamic mass ratio for the model approaches unity for high mass galaxies, but is generally <1 for low mass discs, and this discrepancy appears to follow a similar relationship to that shown in recent work on the Radial Acceleration Relation (RAR). Although this may support Modified Newtonian Dynamics (MOND) in preference to a Dark Matter (DM) halo, it does not exclude undetected baryonic mass or a gravitational DM component in the disc. Full article
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Review

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Open AccessReview
Debated Models for Galactic Rotation Curves: A Review and Mathematical Assessment
Galaxies 2020, 8(2), 47; https://doi.org/10.3390/galaxies8020047 - 01 Jun 2020
Cited by 2 | Viewed by 1959
Abstract
Proposed explanations of galactic rotation curves (RC = tangential velocity vs. equatorial radius, determined from Doppler measurements) involve dramatically different assumptions. A dominant, original camp invoked huge amounts of unknown, non-baryonic dark matter (NBDM) in surrounding haloes to reconcile RC simulated using their [...] Read more.
Proposed explanations of galactic rotation curves (RC = tangential velocity vs. equatorial radius, determined from Doppler measurements) involve dramatically different assumptions. A dominant, original camp invoked huge amounts of unknown, non-baryonic dark matter (NBDM) in surrounding haloes to reconcile RC simulated using their Newtonian orbital models (NOMs) for billions of stars in spiral galaxies with the familiar Keplerian orbital patterns of the few, tiny planets in our Solar System. A competing minority proposed that hypothetical, non-relativistic, non-Newtonian forces govern the internal motions of galaxies. More than 40 years of controversy has followed. Other smaller groups, unsatisfied by explanations rooted in unknown matter or undocumented forces, have variously employed force summations, spin models, or relativistic adaptations to explain galactic rotation curves. Some small groups have pursued inverse models and found no need for NBDM. The successes, failures, and underlying assumptions of the above models are reviewed in this paper, focusing on their mathematical underpinnings. We also show that extractions of RC from Doppler measurements need revising to account for the effect of galaxy shape on flux-velocity profiles and for the possible presence of a secondary spin axis. The latter is indicated by complex Doppler shift patterns. Our findings, combined with independent evidence such as hadron collider experiments failing to produce non-baryonic matter, suggest that a paradigm shift is unfolding. Full article
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Open AccessReview
Rotation Curve of the Milky Way and the Dark Matter Density
Galaxies 2020, 8(2), 37; https://doi.org/10.3390/galaxies8020037 - 29 Apr 2020
Cited by 20 | Viewed by 1810
Abstract
We review the current status of the study of rotation curve (RC) of the Milky Way, and present a unified RC from the Galactic Center to the galacto-centric distance of about 100 kpc. The RC is used to directly calculate the distribution of [...] Read more.
We review the current status of the study of rotation curve (RC) of the Milky Way, and present a unified RC from the Galactic Center to the galacto-centric distance of about 100 kpc. The RC is used to directly calculate the distribution of the surface mass density (SMD). We then propose a method to derive the distribution of dark matter (DM) density in the in the Milky Way using the SMD distribution. The best-fit dark halo profile yielded a local DM density of ρ = 0.36 ± 0.02 GeV cm 3 . We also review the estimations of the local DM density in the last decade, and show that the value is converging to a value at ρ = 0.39 ± 0.09 GeV cm 3 . Full article
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Open AccessReview
Predictions and Outcomes for the Dynamics of Rotating Galaxies
Galaxies 2020, 8(2), 35; https://doi.org/10.3390/galaxies8020035 - 24 Apr 2020
Cited by 13 | Viewed by 1315
Abstract
A review is given of a priori predictions made for the dynamics of rotating galaxies. One theory—MOND—has had many predictions corroborated by subsequent observations. While it is sometimes possible to offer post hoc explanations for these observations in terms of dark matter, it [...] Read more.
A review is given of a priori predictions made for the dynamics of rotating galaxies. One theory—MOND—has had many predictions corroborated by subsequent observations. While it is sometimes possible to offer post hoc explanations for these observations in terms of dark matter, it is seldom possible to use dark matter to predict the same phenomena. Full article
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Open AccessReview
Rotating Disk Galaxies without Dark Matter Based on Scientific Reasoning
Galaxies 2020, 8(1), 9; https://doi.org/10.3390/galaxies8010009 - 01 Feb 2020
Cited by 2 | Viewed by 1301
Abstract
The most cited evidence for (non-baryonic) dark matter has been an apparent lack of visible mass to gravitationally support the observed orbital velocity of matter in rotating disk galaxies, yet measurement of the mass of celestial objects cannot be straightforward, requiring theories derived [...] Read more.
The most cited evidence for (non-baryonic) dark matter has been an apparent lack of visible mass to gravitationally support the observed orbital velocity of matter in rotating disk galaxies, yet measurement of the mass of celestial objects cannot be straightforward, requiring theories derived from the known physical laws along with some empirically established semi-quantitative relationship. The most reliable means for determining the mass distribution in rotating disk galaxies is to solve a force balance equation according to Newton’s laws from measured rotation curves, similar to calculating the Sun’s mass from the Earth’s orbital velocity. Another common method to estimate galactic mass distribution is to convert measured brightness from surface photometry based on empirically established mass-to-light ratio. For convenience, most astronomers commonly assumed a constant mass-to-light ratio for estimation of the so-called “luminous” or “visible” mass, which would not likely be accurate. The mass determined from a rotation curve typically exhibits an exponential-like decline with galactrocentric distance, qualitatively consistent with observed surface brightness but often with a larger disk radial scale length. This fact scientifically suggests variable mass-to-light ratio of baryonic matter in galaxies without the need for dark matter. Full article
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