scholarly journals A fundamental test for MOND

2020 ◽  
Vol 494 (2) ◽  
pp. 2875-2885 ◽  
Author(s):  
Valerio Marra ◽  
Davi C Rodrigues ◽  
Álefe O F de Almeida
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Basic Assumption ◽  
Robust Method ◽  
Rotation Curves ◽  
Radial Acceleration ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Credible Intervals ◽  
Galaxy Rotation Curves

ABSTRACT The radial acceleration relation (RAR) shows a strong correlation between two accelerations associated with galaxy rotation curves. The relation between these accelerations is given by a non-linear function that depends on an acceleration scale a†. Some have interpreted this as an evidence for a gravity model, such as modified Newtonian dynamics (MOND), which posits a fundamental acceleration scale a0 common to all the galaxies. However, it was later shown, using Bayesian inference, that this seems not to be the case: the a0 credible intervals for individual galaxies were not found to be compatible among themselves. A test like the latter is a fundamental test for MOND as a theory for gravity, since it directly evaluates its basic assumption and this using the data that most favour MOND: galaxy rotation curves. Here we improve upon the previous analyses by introducing a more robust method to assess the compatibility between the credible intervals, in particular without Gaussian approximations. We directly estimate, using a Monte Carlo simulation, that the existence of a fundamental acceleration is incompatible with the data at more than 5σ. We also consider quality cuts in order to show that our results are robust against outliers. In conclusion, the new analysis further supports the claim that the acceleration scale found in the RAR is an emergent quantity.

scholarly journals Halo acceleration relation

2019 ◽  
Vol 488 (1) ◽  
pp. L41-L46 ◽  
Author(s):  
Yong Tian (田雍) ◽  
Chung-Ming Ko (高仲明)
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Rotation Curves ◽  
Radial Acceleration ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Total Acceleration

ABSTRACT Recently, from the new Spitzer Photometry and Accurate Rotation Curves data, McGaugh, Lelli & Schombert reported a tight radial acceleration relation between the observed total acceleration and the acceleration produced by baryons in spiral galaxies. The relation can be fitted by different functions. However, these functions can be discerned if we express the data in the form of a halo acceleration relation. The data reveals a maximum in the halo acceleration. We examined the NFW (cusp) and Burkert (core) profiles in the context of dark matter and different parameter families of the interpolating function in the framework of modified Newtonian dynamics.

scholarly journals Fitting the radial acceleration relation to individual SPARC galaxies

2018 ◽  
Vol 615 ◽  
pp. A3 ◽  
Author(s):  
Pengfei Li ◽  
Federico Lelli ◽  
Stacy McGaugh ◽  
James Schombert
Keyword(s):  
Monte Carlo ◽  
Markov Chain ◽  
Markov Chain Monte Carlo ◽  
Monte Carlo Method ◽  
Stellar Mass ◽  
Radial Acceleration ◽  
Critical Acceleration ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
The Mean

Galaxies follow a tight radial acceleration relation (RAR): the acceleration observed at every radius correlates with that expected from the distribution of baryons. We use the Markov chain Monte Carlo method to fit the mean RAR to 175 individual galaxies in the SPARC database, marginalizing over stellar mass-to-light ratio (ϒ⋆), galaxy distance, and disk inclination. Acceptable fits with astrophysically reasonable parameters are found for the vast majority of galaxies. The residuals around these fits have an rms scatter of only 0.057 dex (~13%). This is in agreement with the predictions of modified Newtonian dynamics (MOND). We further consider a generalized version of the RAR that, unlike MOND, permits galaxy-to-galaxy variation in the critical acceleration scale. The fits are not improved with this additional freedom: there is no credible indication of variation in the critical acceleration scale. The data are consistent with the action of a single effective force law. The apparent universality of the acceleration scale and the small residual scatter are key to understanding galaxies.

scholarly journals Newtonian Fractional-dimension Gravity and Rotationally Supported Galaxies

2021 ◽  
Author(s):  
Gabriele U Varieschi
Keyword(s):  
Fractional Dimension ◽  
Newtonian Gravity ◽  
Axially Symmetric ◽  
Local Dimension ◽  
Radial Acceleration ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
The Subject ◽  
Symmetric Structures ◽  
Natural Scale

Abstract We continue our analysis of Newtonian Fractional-Dimension Gravity, an extension of the standard laws of Newtonian gravity to lower dimensional spaces including those with fractional (i.e., non-integer) dimension. We apply our model to three rotationally supported galaxies: NGC 7814 (Bulge-Dominated Spiral), NGC 6503 (Disk-Dominated Spiral), and NGC 3741 (Gas-Dominated Dwarf). As was done in the general cases of spherically-symmetric and axially-symmetric structures, which were studied in previous work on the subject, we examine a possible connection between our model and Modified Newtonian Dynamics, a leading alternative gravity model which explains the observed properties of these galaxies without requiring the Dark Matter hypothesis. In our model, the MOND acceleration constant a0 ≃ 1.2 × 10−10m s−2 can be related to a natural scale length l0, namely $a_{0} \approx GM/l_{0}^{2}$ for a galaxy of mass M. Also, the empirical Radial Acceleration Relation, connecting the observed radial acceleration gobs with the baryonic one gbar, can be explained in terms of a variable local dimension D. As an example of this methodology, we provide detailed rotation curve fits for the three galaxies mentioned above.

Rotation Curves of Ursa Major Galaxies in the Context of Modified Newtonian Dynamics

1998 ◽  
Vol 503 (1) ◽  
pp. 97-108 ◽  
Author(s):  
R. H. Sanders ◽  
M. A. W. Verheijen
Keyword(s):  
Rotation Curves ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics

scholarly journals The Effects of Inertial Forces on the Dynamics of Disk Galaxies

2021 ◽  
Author(s):  
Tomer Zimmerman ◽  
Roy Gomel
Keyword(s):  
Basic Assumption ◽  
Large Range ◽  
Galactic Rotation ◽  
Disk Galaxies ◽  
Dark Halo ◽  
Inertial Forces ◽  
Inertial Effects ◽  
Rotation Curves ◽  
New Model ◽  
Galaxy Rotation Curves

When dealing with galactic dynamics, or more specifically, with galactic rotation curves, one basic assumption is always taken: the frame of reference relative to which the rotational velocities are given is assumed to be inertial. In other words, fictitious forces are assumed to vanish relative to the observational frame of a given galaxy. It might be interesting, however, to explore the outcomes of dropping that assumption; that is, to search for signatures of non-inertial behavior in the observed data. In this work, we show that the very discrepancy in galaxy rotation curves could be attributed to non-inertial effects. We derive a model for spiral galaxies that takes into account the possible influence of fictitious forces and find that the additional terms in the new model, due to fictitious forces, closely resemble dark halo profiles. Following this result, we apply the new model to a wide sample of galaxies, spanning a large range of luminosities and radii. It turns out that the new model accurately reproduces the structures of the rotation curves and provides very good fittings to the data.

scholarly journals Modelling the Rising Tails of Galaxy Rotation Curves

2019 ◽  
Author(s):  
Fan Zhang
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Weak Field ◽  
Rotation Curves ◽  
Gravitational Fields ◽  
Modified Newtonian Dynamics ◽  
Rotation Periods ◽  
Weak Field Limit ◽  
Modified Gravity Theories ◽  
Galaxy Rotation Curves

It is well known but under-appreciated in astrophysical applications, that it is possible for gravity to take on a life of its own in the form of Weyl-curvature-only metrics (note we are referring to the Weyl-only solutions of ordinary General Relativity, we are not considering Weyl conformal gravity or any other modified gravity theories), as numerous examples demonstrate the existence of gravitational fields not being sourced by any matter. In the weak field limit, such autonomous gravitational contents of our universe manifest as solutions to the homogeneous Poisson's equation. In this note, we tentatively explore the possibility that they may perhaps account for some phenomenologies commonly attributed to dark matter. Specifically, we show that a very simple solution of this kind exists that can be utilized to describe the rising tails seen in many galaxy rotation curves, which had been difficult to reconcile within the cold dark matter or modified Newtonian dynamics frameworks. This solution may also help explain the universal $\sim 1$Gyr rotation periods of galaxies in the local universe.

scholarly journals Modelling the Rising Tails of Galaxy Rotation Curves

2018 ◽  
Author(s):  
Fan Zhang
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Weak Field ◽  
Rotation Curves ◽  
Gravitational Fields ◽  
Modified Newtonian Dynamics ◽  
Rotation Periods ◽  
Weak Field Limit ◽  
Modified Gravity Theories ◽  
Galaxy Rotation Curves

It is well known but under-appreciated in astrophysical applications, that it is possible for gravity to take on a life of its own in the form of Weyl-curvature-only metrics (note we are referring to the Weyl-only solutions of ordinary General Relativity, we are not considering Weyl conformal gravity or any other modified gravity theories), as numerous examples demonstrate the existence of gravitational fields not being sourced by any matter. In the weak field limit, such autonomous gravitational contents of our universe manifest as solutions to the homogeneous Poisson's equation. In this note, we tentatively explore the possibility that they may perhaps account for some phenomenologies commonly attributed to dark matter. Specifically, we show that a very simple solution of this kind exists that can be utilized to describe the rising tails seen in many galaxy rotation curves, which had been difficult to reconcile within the cold dark matter or modified Newtonian dynamics frameworks. This solution may also help explain the universal $\sim 1$Gyr rotation periods of galaxies in the local universe.

Modified Newtonian Dynamics Rotation Curves of Very Low Mass Spiral Galaxies

2007 ◽  
Vol 658 (1) ◽  
pp. L17-L20 ◽  
Author(s):  
Mordehai Milgrom ◽  
Robert H. Sanders
Keyword(s):  
Spiral Galaxies ◽  
Rotation Curves ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Low Mass

scholarly journals A method for discriminating between dark matter models and MOND modified inertia via galactic rotation curves

2020 ◽  
Vol 496 (2) ◽  
pp. 1077-1091
Author(s):  
Jonas Petersen ◽  
Mads T Frandsen
Keyword(s):  
Dark Matter ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Baryonic Matter ◽  
Rotation Curves ◽  
Density Profiles ◽  
Closed Curves ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Systematic Uncertainties

ABSTRACT Dark matter (DM) and modified Newtonian dynamics (MOND) models of rotationally supported galaxies lead to curves with different geometries in (gN, gtot)-space (g2-space). Here, gtot is the total acceleration and gN is the acceleration as obtained from the baryonic matter via Newtonian dynamics. In MOND modified inertia (MI) models, the curves in g2-space are closed with zero area and so curve segments at radii r ≥ rN (large radii) and r < rN (small radii) coincide, where rN is the radius where gN is greatest. In DM models with cored density profiles where gtot is also zero at the Galactic Centre, the curves are again closed, but the area of the closed curves are in general non-zero because the curve segments at radii r ≥ rN and r < rN do not coincide. Finally in DM models with cuspy density profiles such as the NFW profile where gtot is formally non-zero at the galactic origin the curves are open, and again the curve segments at radii r ≥ rN and r < rN do not coincide. We develop a test of whether data at small and large radii coincide and investigate rotation curves from the SPARC data base in order to discriminate between the above geometries. Due to loosely quantified systematic uncertainties, we do not underline the result of the test, but instead conclude that the test illustrates the relevance of this type of analysis and demonstrate the ability to discriminate between the considered DM and MI models in this way.

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