Dark Matter: Could It Be Vacuum Viscosity?

2020 ◽  
Vol 13 (1) ◽  
pp. 47-57
Keyword(s):  
Dark Matter ◽  
Simple Model ◽  
Drag Force ◽  
Spiral Galaxies ◽  
Viscous Drag ◽  
Rotation Curves ◽  
The Galaxy ◽  
Viscous Drag Force ◽  
Matter Effect ◽  
Good Agreement

We test a hypothesis that stars located away from the center of the galaxy, moving under the effect of an emergent viscous drag force perpendicular to their velocities, might exhibit the behavior observed in the rotation curves of the spiral galaxies. We construct a simple model for such an assumption, then by using simple fitting technique, we are able to produce the rotation curves for a sample of 18 spiral galaxies. Results show good agreement with the observed rotation curves. The applicability of our hypothesis suggests that an emergent drag force perpendicular to the velocity of the stars might be the cause of the apparent dark matter effect.

scholarly journals Newtonian and modified newtonian gravitational simulation of spiral galaxies

2019 ◽  
Vol 11 (21) ◽  
pp. 20-27
Author(s):  
Bushra A. Ahmed
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Stellar Dynamics ◽  
Gravitational Attraction ◽  
Rotation Curves ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Rotational Curve ◽  
Good Agreement

One of the most powerful tools for any stellar dynamics is the N-body simulation. In an N-body simulation the motion of N particles is followed under their mutual gravitational attraction. In this paper the gravitational N-body simulation is described to investigate Newtonian and non- Newtonian (modified Newtonian dynamics) interaction between the stars of spiral galaxies. It is shown that standard Newtonian interaction requires dark matter to produce the flat rotational curves of the systems under consideration, while modified Newtonian dynamics (MOND) theorem provides a flat rotational curve and gives a good agreement with the observed rotation curve; MOND was tested as an alternative to the dark matter hypothesis. So that MOND hypothesis has generated better rotation curves than Newtonian theorem.

scholarly journals The Massive Dark Corona Of Our Galaxy

1996 ◽  
Vol 173 ◽  
pp. 175-176
Author(s):  
K.C. Freeman
Keyword(s):  
Rotation Curve ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Disk ◽  
Galactic Rotation ◽  
Rotation Curves ◽  
Stellar Component ◽  
The Galaxy ◽  
Galactic Rotation Curve

From their rotation curves, most spiral galaxies appear to have massive dark coronas. The inferred masses of these dark coronas are typically 5 to 10 times the mass of the underlying stellar component. I will review the evidence that our Galaxy also has a dark corona. Our position in the galactic disk makes it difficult to measure the galactic rotation curve beyond about 20 kpc from the galactic center. However it does allow several other indicators of the total galactic mass out to very large distances. It seems clear that the Galaxy does indeed have a massive dark corona. The data indicate that the enclosed mass within radius R increases like M(R) ≈ R(kpc) × 1010M⊙, out to a radius of more than 100 kpc. The total galactic mass is at least 12 × 1011M⊙.

Studying the Patterns of the Universe

2011 ◽  
Vol 20 (2) ◽  
Author(s):  
T. Sepp ◽  
E. Tempel ◽  
M. Gramann ◽  
P. Nurmi ◽  
M. Haupt
Keyword(s):  
Dark Matter ◽  
Galaxy Cluster ◽  
Analytical Models ◽  
Matter Distribution ◽  
Galaxy Groups ◽  
The Galaxy ◽  
Dark Matter Distribution ◽  
Distribution Studies ◽  
The Universe ◽  
Good Agreement

AbstractThe SDSS galaxy catalog is one of the best databases for galaxy distribution studies. The SDSS DR8 data is used to construct the galaxy cluster catalog. We construct the clusters from the calculated luminosity density field and identify denser regions. Around these peak regions we construct galaxy clusters. Another interesting question in cosmology is how observable galaxy structures are connected to underlying dark matter distribution. To study this we compare the SDSS DR7 galaxy group catalog with galaxy groups obtained from the semi-analytical Millennium N-Body simulation. Specifically, we compare the group richness, virial radius, maximum separation and velocity dispersion distributions and find a relatively good agreement between the mock catalog and observations. This strongly supports the idea that the dark matter distribution and galaxies in the semi-analytical models and observations are very closely linked.

The numerical study of viscous drag force influence on low-frequency surge motion of a semi-submersible in storm sea states

2020 ◽  
Vol 213 ◽  
pp. 107511 ◽  
Author(s):  
Shan Ma ◽  
De-kang Xu ◽  
Wen-yang Duan ◽  
Ji-kang Chen ◽  
Kang-ping Liao ◽  
...  
Keyword(s):  
Drag Force ◽  
Numerical Study ◽  
Low Frequency ◽  
Viscous Drag ◽  
Viscous Drag Force

scholarly journals Galaxy rotation curves using a non-parametric regression method: core, cuspy and fuzzy scalar field dark matter models

2019 ◽  
Vol 488 (4) ◽  
pp. 5127-5144 ◽  
Author(s):  
Lizbeth M Fernández-Hernández ◽  
Ariadna Montiel ◽  
Mario A Rodríguez-Meza
Keyword(s):  
Dark Matter ◽  
Selection Criteria ◽  
Spiral Galaxies ◽  
Information Criterion ◽  
Volume Density ◽  
Rotation Curves ◽  
Fuzzy Models ◽  
Galaxy Rotation Curves ◽  
Statistical Criteria ◽  
Non Parametric

ABSTRACT We present a non-parametric reconstruction of the rotation curves (RCs) for 88 spiral galaxies using the LOESS (locally weighted scatterplot smoothing) + SIMEX (simulation and extrapolation) technique. In order to compare methods, we also use a parametric approach, assuming core and cuspy dark matter (DM) profiles: pseudo-isothermal (PISO), Navarro−Frenk–White (NFW), Burkert, Spano, the soliton, and two fuzzy soliton + NFW. As a result of these two approaches, a comparison of the RCs obtained is carried out by computing the distance between the central curves and the distance between the 1σ error bands. Furthermore, we perform a model selection according to two statistical criteria, the Bayesian information criterion and the value of $\chi ^2_{\rm red}$. We work with two groups. The first is a comparison between PISO, NFW, Spano and Burkert, showing that Spano is the most favoured model satisfying our selection criteria. For the second group, we select the soliton, NFW and fuzzy models, resulting in soliton as the best model. Moreover, according to the statistical tools and non-parametric reconstruction, we are able to classify galaxies as core or cuspy. Finally, using a Markov chain Monte Carlo method, for each of the DM models we compute the characteristic surface density, μDM = ρsrs, and the mass within 300 pc. We find that there is a common mass for spiral galaxies of the order of 107 M⊙, which is in agreement with results for dSph Milky Way satellites, independent of the model. This result is also consistent with our finding that there is a constant characteristic volume density of haloes. Finally, we also find that μDM is not constant, which is in tension with the literature.

scholarly journals Cores vs. Cusps: Dark Matter Density Profiles in Spirals

2004 ◽  
Vol 220 ◽  
pp. 311-312
Author(s):  
Gianfranco Gentile ◽  
Uli Klein ◽  
Paolo Salucci ◽  
Daniela Vergani
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Matter Density ◽  
Matter Distribution ◽  
Rotation Curves ◽  
Density Profiles ◽  
The Core ◽  
Dark Matter Distribution ◽  
A New Technique

We use photometric, Hα and Hi data to investigate the distribution of dark matter in spiral galaxies. A new technique for deriving the Hi rotation curve is presented. the final combined Hα+Hi rotation curves are symmetric, well resolved and extend to large radii. We perform the rotation curve decomposition into the luminous and dark matter contributions. the observations are confronted with different models of the dark matter distribution, including core-dominated and cusp-dominated halos as well as less conventional possibilities. the best agreement with the observations is found for the core-dominated halos.

scholarly journals Constraints on the Dark Matter from Optical Rotation Curves

1987 ◽  
Vol 117 ◽  
pp. 51-65 ◽  
Author(s):  
Vera C. Rubin
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Optical Rotation ◽  
Optical Image ◽  
Rotation Curves

From the observed rotation curves of Sa, Sb, and Sc spiral galaxies, it is possible to deduce a dozen constraints on the nonluminous matter in spirals. Within the optical image, the dark matter is less concentrated than the luminous, and contributes about 1/2 of the mass, for spirals of all Hubble types and luminosities.

scholarly journals Tidal Dwarf Galaxies and Missing Baryons

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Frederic Bournaud
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Rotation Curves ◽  
Cosmological Problem ◽  
Flat Rotation Curves ◽  
Mass Size ◽  
Merger Rate ◽  
The Universe

Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

THE GENERATION MODEL OF PARTICLE PHYSICS AND GALACTIC DARK MATTER

2013 ◽  
Vol 22 (09) ◽  
pp. 1350067 ◽  
Author(s):  
B. A. ROBSON
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Spiral Galaxies ◽  
Generation Model ◽  
Universal Gravitation ◽  
Strong Argument ◽  
Newton's Law ◽  
Newton’S Law ◽  
Galactic Dark Matter ◽  
The Galaxy

Galactic dark matter is matter hypothesized to account for the discrepancy of the mass of a galaxy determined from its gravitational effects, assuming the validity of Newton's law of universal gravitation, and the mass calculated from the "luminous matter", stars, gas, dust, etc. observed to be contained within the galaxy. The conclusive observation from the rotation curves of spiral galaxies that the mass discrepancy is greater, the larger the distance scales involved implies that either Newton's law of universal gravitation requires modification or considerably more mass (dark matter) is required to be present in each galaxy. Both the modification of Newton's law of gravitation and the hypothesis of the existence of considerable dark matter in a galaxy are discussed. It is shown that the Generation Model (GM) of particle physics, which leads to a modification of Newton's law of gravitation, is found to be essentially equivalent to that of Milgrom's modified Newtonian dynamics (MOND) theory, with the GM providing a physical understanding of the MOND theory. The continuing success of MOND theory in describing the extragalactic mass discrepancy problems constitutes a strong argument against the existence of undetected dark matter haloes, consisting of unknown nonbaryonic matter, surrounding spiral galaxies.

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