The dynamics of galaxies and the 'missing mass' problem

1980 ◽  
Vol 296 (1419) ◽  
pp. 313-318 ◽  
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Simple Theory ◽  
Missing Mass ◽  
Mass Problem ◽  
The Galaxy ◽  
Dynamics Of Galaxies ◽  
New Evidence

I review the observational situation concerning the existence of dark matter in the outer parts of galaxies. Observation now leaves little doubt of its presence, and both observation and simple theory suggest that the dark matter is probably bound to galaxies, and furthermore is present around both spirals and ellipticals. New evidence concerning the rotation curve of the Galaxy shows that the distribution of the halo stuff in our own system is roughly spherical, as seems natural from existing dynamical data on the nature of the halo material.

scholarly journals Some Regularities in the Missing Mass Problem

1987 ◽  
Vol 117 ◽  
pp. 136-136
Author(s):  
S. Casertano ◽  
J. N. Bahcall
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Full Description ◽  
Mass Model ◽  
Missing Mass ◽  
Mass Problem ◽  
Available Information ◽  
Optical Radius

We discuss available information on the distribution of luminous and dark matter in eight galaxies. The galaxies have been chosen according to the following criteria: 1) existence of a good rotation curve, extending well beyond the optical radius; 2) a mass model has been published; 3) valuable constraints can be put on the amount of dark matter inside the optical radius. A full description of the data and reduction procedures is in Bahcall and Casertano (1985).

DARK GEOMETRY

2004 ◽  
Vol 13 (10) ◽  
pp. 2275-2279 ◽  
Author(s):  
J. A. R. CEMBRANOS ◽  
A. DOBADO ◽  
A. L. MAROTO
Keyword(s):  
Dark Matter ◽  
Extra Dimensions ◽  
Degrees Of Freedom ◽  
Planck Scale ◽  
Point Of View ◽  
Missing Mass ◽  
Brane Worlds ◽  
Mass Problem ◽  
Extra Space ◽  
The Universe

Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space–time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.

Electromagnetic gravitational shielding to explain dark matter

2020 ◽  
Author(s):  
Matheus Pereira Lobo
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Electromagnetic Theory ◽  
Electromagnetic Interactions ◽  
The Galaxy

There is only one of two possibilities: (i) either dark matter exists or dark matter does not exist. We consider one single conjecture, valid in both cases. If it doesn’t exist, then huge quantum electromagnetic interactions might account for the galaxy rotation curve. If it exists, then there might be a “dark charge” associated with dark matter. The dark charge would then be governed by an alternative “dark electromagnetic” theory, which can be totally independent or perhaps a generalization of the ordinary electromagnetism. This proposal is highly speculative and it needs both mathematical and experimental further investigation in order to be proved or disproved.

scholarly journals The ‘Missing Mass Problem’ in Astronomy and the Need for a Modified Law of Gravity

2014 ◽  
Vol 69 (3-4) ◽  
pp. 173-187 ◽  
Author(s):  
Sascha Trippe
Keyword(s):  
Dark Matter ◽  
Stellar Dynamics ◽  
Stellar Systems ◽  
Gravitational Acceleration ◽  
Missing Mass ◽  
Astronomical Observations ◽  
Groups Of Galaxies ◽  
Mass Problem ◽  
Multiple Observations ◽  
Law Of Gravity

Since the 1930s, astronomical observations have accumulated evidence that our understanding of the dynamics of galaxies and groups of galaxies is grossly incomplete: assuming the validity of Newton’s law of gravity on astronomical scales, the observed mass (stored in stars and interstellar gas) of stellar systems can account only for roughly 10% of the dynamical (gravitating) mass required to explain the high velocities of stars in those systems. The standard approach to this ‘missing mass problem’ has been the postulate of ‘dark matter’, meaning an additional, electromagnetically dark, matter component that provides the missing mass. However, direct observational evidence for dark matter has not been found to date. More importantly, astronomical observations obtained during the last decade indicate that dark matter cannot explain the kinematics of galaxies. Multiple observations show that the discrepancy between observed and dynamical mass is a function of gravitational acceleration (or field strength) but not of other parameters (size, rotation speed, etc.) of a galaxy; the mass discrepancy appears below a characteristic and universal acceleration aM = (1:1±0:1) · 10-10 ms-2 (Milgrom’s constant). Consequently, the idea of a modified law of gravity, specifically the ansatz of modified Newtonian dynamics (MOND), is becoming increasingly important in astrophysics. MOND has successfully predicted various important empirical relations of galaxy dynamics, including the famous Tully-Fisher and Faber-Jackson relations. MOND is found to be consistent with stellar dynamics from binary stars to clusters of galaxies, thus covering stellar systems spanning eight orders of magnitude in size and 14 orders of magnitude in mass. These developments have the potential to initiate a paradigm shift from dark matter to a modified law of gravity as the physical mechanism behind the missing mass problem.

scholarly journals A 5° × 5° deep H i survey of the M81 group − II. H i distribution and kinematics of IC 2574 and HIJASS J1021+68

2020 ◽  
Vol 493 (2) ◽  
pp. 2618-2631
Author(s):  
A Sorgho ◽  
L Chemin ◽  
Z S Kam ◽  
T Foster ◽  
C Carignan
Keyword(s):  
Dark Matter ◽  
Velocity Distribution ◽  
Rotation Curve ◽  
Dwarf Galaxy ◽  
Dark Matter Halo ◽  
Eastern Region ◽  
Ring Model ◽  
The Galaxy ◽  
Group Ii

ABSTRACT We analyse the eastern region of a 5° × 5° deep H i survey of the M81 group containing the dwarf galaxy IC 2574 and the H i complex HIJASS J1021+68, located between the dwarf and the M81 system. The data show that IC 2574 has an extended H i envelope that connects to HIJASS J1021+68 in the form of a collection of small clouds, but no evident connection has been found between IC 2574 and the central members of the M81 group. We argue, based on the morphology of the clouds forming HIJASS J1021+68 and its velocity distribution, that the complex is not a dark galaxy as previously suggested, but is instead a complex of clouds either stripped from, or falling on to the primordial H i envelope of IC 2574. We also use the deep H i observations to map the extended H i envelope around IC 2574 and, using a 3D tilted-ring model, we derive the rotation curve of the galaxy to a larger extent than has been done before. Combining the obtained rotation curve to higher resolution curves from the literature, we constrain the galaxy’s dark matter halo parameters.

scholarly journals Cluster Swapping

1988 ◽  
Vol 126 ◽  
pp. 297-309
Author(s):  
Juan C. Muzzio
Keyword(s):  
Gravitational Field ◽  
Numerical Simulations ◽  
Globular Cluster ◽  
Total Mass ◽  
Dynamical Evolution ◽  
Clusters Of Galaxies ◽  
Missing Mass ◽  
Mass Problem ◽  
Test Particles ◽  
The Galaxy

The investigation of globular cluster swapping in clusters of galaxies has resulted in some interesting theoretical findings and, at the same time, it offers a promising field for observers. Numerical simulations of galaxy clusters where the galaxies have swarms of test particles around them showed that, in addition to tidal stripping, tidal accretion plays an important role in the dynamical evolution of clusters of galaxies; it also turns out that, even in clusters where the gravitational field is dominated by a massive background, the galaxy-galaxy attraction cannot be ignored when estimating the outcome of collisions. Cluster swapping is just an example of tidal accretion and, taking the globulars as probes of halo material, it might offer an opportunity to observe some consequences of that effect; besides, although the difficulties look formidable at present, the study of globulars lost through tidal stripping is a possibility that should not be neglected. Tidal stripping and accretion processes are very sensitive to the ratio of galactic mass to total mass, so that observations related to the cluster swapping phenomena may provide a new means to investigate the missing mass problem.

scholarly journals The Modification of Newton's Gravitational Law and its Application in the Study of Dark Matter and Black Hole

2021 ◽  
Author(s):  
Jian'an Wang
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Field Intensity ◽  
Space Time ◽  
Missing Mass ◽  
Energy Field ◽  
Supermassive Black Hole ◽  
The Galaxy

Abstract In this paper, Newton's gravitational formula is modified by the principle of spatial energy field superposition, and the problem of "missing mass " of galaxies is analyzed by this modified gravitational formula. It is concluded that the velocity of stars in the galaxy is too fast because the energy field intensity of the inner space of the galaxy or space-time curvature of the galaxy is seriously underestimated, and there is no dark matter and supermassive black hole in the galaxy.

scholarly journals Galactic Evolution Showing a Constant Circulating Speed of Stars in a Galactic Disc without Requiring Dark Matter

2020 ◽  
pp. 2050004
Author(s):  
Shigeto Nagao
Keyword(s):  
Dark Matter ◽  
Rotation Curve ◽  
Rotation Velocity ◽  
Initial Energy ◽  
Galactic Evolution ◽  
Initial Speed ◽  
Galactic Disc ◽  
The Galaxy ◽  
Space Expansion ◽  
Circulation Theory

It is an unsolved mystery that the rotation velocity of a galactic disc is same at any radial distances. The presence of dark matter is expected, but not observed. Here we propose a novel scheme for the evolution of the initial cosmic energy to current galaxies. According to the energy circulation theory, which we previously reported, the fundamental force works based on momentums. Antiparallel movements of energy pieces form a circulation. Due to the space expansion, the initial energy circulations separate and decompose to smaller level circulations; to galactic seeds, stellar seeds, and smallest energy circulations. The internal circulating velocity of a galactic seed is inherited to the circulating speed of stellar seeds in a ring. The intra-circulation interaction by the fundamental force keeps the stellar seeds to circulate at the initial speed, which does not alter by the space expansion. The new scheme meets the galaxy rotation curve without requiring dark matter.

scholarly journals Testing MOdified Gravity (MOG) theory and dark matter model in Milky Way using the local observables

2020 ◽  
Vol 496 (3) ◽  
pp. 3502-3511 ◽  
Author(s):  
Zahra Davari ◽  
Sohrab Rahvar
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Rotation Curve ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Curve Surface ◽  
Best Value ◽  
Matter Model ◽  
Dynamics Of Galaxies ◽  
Dark Matter Model

ABSTRACT In this paper, we have investigated one of the alternative theories to dark matter named MOdified Gravity (MOG) by testing its ability to describe the local dynamics of the Milky Way (MW) in vertical and transverse directions with the baryonic matter. MOG is designed to interpret the dynamics of galaxies and cluster of galaxies without the need for dark matter. We use local observational data such as the vertical dispersion, rotation curve, surface density, and number density of stars in the Milky Way to obtain the parameters of MOG and the baryonic component of MW by implementing a Bayesian approach to the parameter estimation based on a Markov Chain Monte Carlo method. We compare our results with the dark matter model of MW. The two models of MOG and cold dark matter are able to describe equally well the rotation curve and the vertical dynamics of stars in the local MW. The best values for the free parameters of MOG in this analysis are obtained as α = 8.99 ± 0.02 and μ = 0.054 ± 0.005 kpc−1. Also, we obtain the parameters of the generalized gNFW model in the dark matter model. Our best value of bulge mass from MOG is $(1.06 \pm 0.26)\times 10^{10}\, \rm M_{\odot }$, which is consistent with the estimations form the microlensing observations.

scholarly journals Detecting dark photons from atomic rearrangement in the galaxy

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
James Eiger ◽  
Michael Geller
Keyword(s):  
Dark Matter ◽  
Ground State ◽  
Bound State ◽  
Current Data ◽  
Dark Sector ◽  
Atomic Process ◽  
The Galaxy ◽  
Atomic States ◽  
Atomic Rearrangement

Abstract We study a new dark sector signature for an atomic process of “rearrangement” in the galaxy. In this process, a hydrogen-like atomic dark matter state together with its anti-particle can rearrange to form a highly-excited bound state. This bound state will then de-excite into the ground state emitting a large number of dark photons that can be measured in experiments on Earth through their kinetic mixing with the photon. We find that for DM masses in the GeV range, the dark photons have enough energy to pass the thresholds of neutrino observatories such as Borexino and Super-Kamiokande that can probe for our scenario even when our atomic states constitute a small fraction of the total DM abundance. We study the corresponding bounds on the parameters of our model from current data as well as the prospects for future detectors.

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