scholarly journals On the plausible origins of the spiral character of galaxies

2021 ◽  
Vol 30 (1) ◽  
pp. 1-11
Author(s):  
Golden Gadzirayi Nyambuya
Keyword(s):  
Spiral Galaxies ◽  
Galactic Disk ◽  
Free Fall ◽  
Rotation Curves ◽  
Flat Rotation Curves ◽  
Central Bulge ◽  
Dark Force ◽  
Train Of Thought

Abstract We here-in demonstrate that the proposed hitherto unknown gravitomagnetic dark-force that hypothetically explains the Flat Rotation Curves of Spiral Galaxies — this same force, explains very well, the logarithmic and as-well, the barred spiral shapes of spiral galaxies. That is, much in line with Edward Arthur Milne (1896-1950)’s 1946 ideas — albeit, on a radically and asymptotically different philosophical train of thought, the galactic disk is here assumed to be in a state of free-fall around the central bulge with the hypothetical gravitomagnetic dark-force being the dominant force determining all gravity-related dynamics of the disk, thus leading to logarithmic and barred spiral orbits, hence the shape of spiral galaxies.

scholarly journals Rotation Curves in the Outer Parts of Galaxies from HI Observations

1978 ◽  
Vol 77 ◽  
pp. 23-31 ◽  
Author(s):  
Edwin E. Salpeter
Keyword(s):  
Spiral Galaxies ◽  
Rotation Curves ◽  
Flat Rotation Curves ◽  
Arecibo Observatory

21cm observations at the Arecibo Observatory for 9 edge-on spiral galaxies are described. Flat rotation curves are found in most cases.

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⊙.

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”.

scholarly journals Vertical Motion and the Thickness of Hi Disks: Implications for Galactic Mass Models

1983 ◽  
Vol 100 ◽  
pp. 69-76
Author(s):  
P. C. van der Kruit ◽  
G. S. Shostak
Keyword(s):  
Dark Matter ◽  
Mass Distribution ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Galactic Plane ◽  
Vertical Motion ◽  
Late Type ◽  
Rotation Curves ◽  
Central Bulge ◽  
Local Value

Most studies of the mass distribution in spiral galaxies have been based on the observed rotation curves. A serious ambiguity in this approach has always been that the rotation curve contains in itself no information on the mass distribution in the direction perpendicular to the galactic plane. The usual assumption has been that the mass in late type galaxies is distributed as the light, namely outside the central bulge in a highly flattened disk. In recent years it has been found that the rotation curves decline little or not at all, indicating large increases in the local value of M/L with increasing galactocentric radius (e.g. Bosma and van der Kruit, 1979). On the basis of dynamical arguments involving stability it has been suspected that the material giving rise to the large values of M/L - the “dark matter” - is distributed in the halos of these galaxies, so that the assumption of a flat mass distribution would have to be wrong.

scholarly journals Does Our Galaxy have a Massive Dark Corona?

1996 ◽  
Vol 169 ◽  
pp. 645-650
Author(s):  
K.C. Freeman
Keyword(s):  
Rotation Curve ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Disk ◽  
Galactic Rotation ◽  
Rotation Curves ◽  
The Galaxy ◽  
Galactic Rotation Curve

The rotation curves of spiral galaxies indicate that most of them have massive dark coronas, and it seems likely 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, but it does allow us to use several other indicators of the total galactic mass out to very large distances. I will review some of these indicators. The conclusion is that the Galaxy does indeed have a massive dark corona: the data are consistent with the enclosed mass within radius R increasing like M(R) ≈ R(kpc) × 1010M⊙, out to a radius of more than 100 kpc, and a total galactic mass of at least 12 × 1011M⊙.

scholarly journals Do All Spiral Galaxies Have a Massive Dark Halo?

1999 ◽  
Vol 183 ◽  
pp. 157-157 ◽  
Author(s):  
M. Honma ◽  
Y. Sofue
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
The Other ◽  
Dark Halo ◽  
Rotation Curves ◽  
Other Hand ◽  
Flat Rotation Curves ◽  
The Masses ◽  
Scale Length

We have investigated the masses and extents of dark halos of spiral galaxies by two methods. First, we have reanalyzed HI outer rotation curves so far obtained considering the velocity uncertainties. We confirmed that many HI rotation curves indicate the existence of dark matter to some extent. However, we also found that only few rotation curves provide direct evidences for halos extended beyond 10 disk scale length. On the other hand, recent HI observations revealed that several galaxies have declining rotation curves that are approximated by Keplerian in the outermost regions. Considering the velocity uncertainties in the outer rotation curves, we found that these declining rotation curves are not rare compared to flat rotation curves. If these declining rotation curves indeed trace the mass truncation, these results indicate that some dark halos have moderate masses that are comparable or slightly larger than disk masses.

Dark matter particles and the flat rotation curves of spiral galaxies

1995 ◽  
Vol 234 (1) ◽  
pp. 69-83 ◽  
Author(s):  
H. Dehnen ◽  
B. Rose ◽  
K. Amer
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Rotation Curves ◽  
Flat Rotation Curves
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