scholarly journals A Derivation of Flat Rotation Curve of Spiral Galaxies and Baryonic Tully-Fisher Relation

2020 ◽  
Author(s):  
Swagatam Sen
Keyword(s):  
Laplace Equation ◽  
Spiral Galaxy ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Rotation Velocity ◽  
Alternative Solution ◽  
The Galaxy ◽  
Flat Rotation Curve ◽  
Disc Region ◽  
Fisher Relation

Fundamentally for the extended disc region of a spiral galaxy, an alternative solution to Laplace equation has been presented for a potential that is radially symmetric on the disc plane. This potential, unlike newtonian one, is shown to be logarithmic in distance from the centre, which allows for the rotation velocity to be constant along the disc radius.It is also shown that this potential easily manifests into a relationship between inner mass of the galaxy and terminal rotation velocity, which has been empirically observed and known as Baryonic Tully-Fisher relations.

scholarly journals On Non-Spherical Models for Spiral Galaxy Gravitation Potential Yielding Flat Rotation Curve

2021 ◽  
Author(s):  
Swagatam Sen
Keyword(s):  
Spiral Galaxies ◽  
Galactic Plane ◽  
Rotation Velocity ◽  
Radial Symmetry ◽  
Galactic Centre ◽  
Spherically Symmetric ◽  
Annular Disk ◽  
Spherical Models ◽  
The Galaxy ◽  
Flat Rotation Curve

Abstract A two component model of gravitation potential for spiral galaxies has been proposed which couples a spherically symmetric component with a second component that observes planar radial symmetry on the galactic plane and vanishes outside an annular disk beyond the edge of galaxy's effective radius. It is shown that such a model for potential satisfying Poisson Equation would produce rotation velocity curve towards the edge of the galaxy which is flat over distance from the galactic centre. This relationship, which is experimentally observed in many spiral galaxies, is shown as a consequence of classical understanding of gravity and specific symmetry of the gravitational potential without any extrinsic requirement of dark matter. It is also demonstrated that this potential directly yields a relationship between inner mass of the galaxy and terminal rotation velocity, which has been empirically observed and known as Baryonic Tully-Fisher relations. Furthermore a direct test has been proposed for experimental verification of the proposed theory.

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 Simple models of galactic bulges

1993 ◽  
Vol 153 ◽  
pp. 361-362
Author(s):  
N.W. Evans
Keyword(s):  
Distribution Function ◽  
Gravity Field ◽  
Rotation Curve ◽  
Logarithmic Potential ◽  
Axisymmetric Model ◽  
The Galaxy ◽  
Flat Rotation Curve ◽  
Simple Models

We present a simple axisymmetric model with an elementary distribution function capable of representing galactic bulges. The gravity field of the galaxy is based on the axisymmetric logarithmic potential, which has a flat rotation curve. Bulges are built as isothermal distributions of stars embedded within the potential.

scholarly journals The Tully-Fisher relation: evolution with redshift and environment

2006 ◽  
Vol 2 (S235) ◽  
pp. 8-11 ◽  
Author(s):  
Alfonso Aragón-Salamanca
Keyword(s):  
Spiral Galaxies ◽  
Rotation Velocity ◽  
Disk Galaxies ◽  
Cluster Galaxies ◽  
Fundamental Properties ◽  
Look Back ◽  
Formation And Evolution ◽  
Fisher Relation

AbstractThe Tully-Fisher Relation (TFR) links two fundamental properties of disk galaxies: their luminosity and their rotation velocity (mass). The pioneering work of Vogt et al. in the 1990's showed that it is possible to study the TFR for spiral galaxies at considerable look-back-times, and use it as a powerful probe of their evolution. In recent years, several groups have studied the TFR for galaxies in different environments reaching redshifts beyond one. In this brief review I summarise the main results of some of these studies and their consequences for our understanding of the formation and evolution of disk galaxies. Particular emphasis is placed on the possible environment-driven differences in the behaviour of the TFR for field and cluster galaxies.

scholarly journals The dual origin of the Galactic thick disc and halo from the gas-rich Gaia–Enceladus Sausage merger

2020 ◽  
Vol 497 (2) ◽  
pp. 1603-1618 ◽  
Author(s):  
Robert J J Grand ◽  
Daisuke Kawata ◽  
Vasily Belokurov ◽  
Alis J Deason ◽  
Azadeh Fattahi ◽  
...  
Keyword(s):  
Rotation Velocity ◽  
Orbital Eccentricity ◽  
Chemical Abundance ◽  
Thick Disc ◽  
Rapid Formation ◽  
The Galaxy ◽  
Stellar Halo ◽  
Disc Region ◽  
Magnetohydrodynamic Simulations ◽  
Dual Origin

ABSTRACT We analyse a set of cosmological magnetohydrodynamic simulations of the formation of Milky Way-mass galaxies identified to have a prominent radially anisotropic stellar halo component similar to the so-called ‘Gaia Sausage’ found in the Gaia data. We examine the effects of the progenitor of the Sausage (the Gaia–Enceladus Sausage, GES) on the formation of major galactic components analogous to the Galactic thick disc and inner stellar halo. We find that the GES merger is likely to have been gas-rich and contribute 10–50 ${{\ \rm per\ cent}}$ of gas to a merger-induced centrally concentrated starburst that results in the rapid formation of a compact, rotationally supported thick disc that occupies the typical chemical thick disc region of chemical abundance space. We find evidence that gas-rich mergers heated the proto-disc of the Galaxy, scattering stars on to less-circular orbits such that their rotation velocity and metallicity positively correlate, thus contributing an additional component that connects the Galactic thick disc to the inner stellar halo. We demonstrate that the level of kinematic heating of the proto-galaxy correlates with the kinematic state of the population before the merger, the progenitor mass, and orbital eccentricity of the merger. Furthermore, we show that the mass and time of the merger can be accurately inferred from local stars on counter-rotating orbits.

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 A Unified Electro-Gravity Theory to Model Spiral Galaxies without Dark Matter

2019 ◽  
Author(s):  
Nirod K. Das
Keyword(s):  
Elementary Particle ◽  
Dark Matter ◽  
Spiral Galaxy ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Rotation Speed ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
The Galaxy ◽  
Flat Rotation Curves

A unified electro-gravity (UEG) theory, which has been successfully used for modeling an elementary particle, is applied in this paper to model gravitation in spiral galaxies. The new UEG model would explain the “flat rotation curves” commonly observed in the spiral galaxies, without need for any hypothetical dark matter. The UEG theory is implemented in a somewhat different manner for a spiral galaxy, as compared to the simple application of the UEG theory to an elementary particle. This is because the spiral galaxy, unlike the elementary particle, is not spherically symmetric. The UEG constant $\gamma$, required in the new model to support the galaxies' flat rotation speeds, is estimated using measured data from a galaxy survey, as well as for a selected galaxy for illustration. The estimates are compared with the $\gamma$ derived from the UEG model of an elementary particle. The UEG model for the galaxy is shown to explain the empirical Tully-Fisher Relationship (TFR), is consistent with the Modified Newtonian Dynamics (MOND), and is also independently supported by measured trends of galaxy thickness with surface brightness and rotation speed.

scholarly journals Theoretical Considerations on the Dynamics of Normal Galactic Nuclei

1980 ◽  
Vol 5 ◽  
pp. 197-204
Author(s):  
Robert H. Sanders
Keyword(s):  
Spatial Distribution ◽  
Gravitational Field ◽  
Mass Distribution ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Neutral Hydrogen ◽  
Galactic Nuclei ◽  
The Galaxy ◽  
Theoretical Considerations ◽  
Normal Spiral

I want to discuss the origin of non-circular gas motions observed in the nuclei of normal spiral galaxies and the possibility that recurring violent activity in normal nuclei excites such motion. But first, let us review several basic aspects of the nearest normal galactic nucleus — the nucleus of our own Galaxy.The rotation curve as observed in the 21-cm line of neutral hydrogen gives some indication of the form of the gravitational field in the central region of the Galaxy. Figure 1 is a smooth fit to the rotation curve in the inner few kiloparsecs (solid line) taken essentially from the data of Rougoor and Oort (1960) and Simonson and Mader (1973). This rotation curve, within 1 kpc of the centre, is completely accounted for by the mass distribution implied by the extended 2.2-μ emission (Becklin and Neugebauer 1968, Oort 1971). Moreover, there is little doubt that this centrally condensed mass distribution should be identified with the bulge or spheroidal component of the Galaxy, because the spatial distribution of the 2.2-μ intensity is practically identical to the distribution of visible starlight in the bulge of M31 (Sandage, Becklin, and Neugebauer 1969). The conclusion is that the bulge overwhelmingly dominates the gravitational field inside of 1 kpc.

scholarly journals DARK MATTER AND DARK ENERGY AS EFFECTS OF MODIFIED GRAVITY

2007 ◽  
Vol 04 (01) ◽  
pp. 183-196 ◽  
Author(s):  
ANDRZEJ BOROWIEC ◽  
WŁODZIMIERZ GODŁOWSKI ◽  
MAREK SZYDŁOWSKI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Information Criteria ◽  
Einstein's Equation ◽  
Flat Rotation Curve ◽  
Nonlinear Lagrangian ◽  
As Effects ◽  
Good Agreement

We explain the effect of dark matter (flat rotation curve) using modified gravitational dynamics. We investigate in this context a low energy limit of generalized general relativity with a nonlinear Lagrangian [Formula: see text], where R is the (generalized) Ricci scalar and n is parameter estimated from SNIa data. We estimate parameter β in modified gravitational potential [Formula: see text]. Then we compare value of β obtained from SNIa data with β parameter evaluated from the best fitted rotation curve. We find β ≃ 0.7 which becomes in good agreement with an observation of spiral galaxies rotation curve. We also find preferred value of Ωm,0 from the combined analysis of supernovae data and baryon oscillation peak. We argue that although amount of "dark energy" (of non-substantial origin) is consistent with SNIa data and flat curves of spiral galaxies are reproduces in the framework of modified Einstein's equation we still need substantial dark matter. For comparison predictions of the model with predictions of the ΛCDM concordance model we apply the Akaike and Bayesian information criteria of model selection.

scholarly journals Rotation curves of high-luminosity spiral galaxies and the rotation curve of our galaxy

1979 ◽  
Vol 84 ◽  
pp. 211-220 ◽  
Author(s):  
Vera C. Rubin
Keyword(s):  
Rotation Curve ◽  
Spiral Galaxies ◽  
Rotational Velocity ◽  
Density Wave ◽  
Wave Theory ◽  
High Luminosity ◽  
Rotation Curves ◽  
Flat Rotation Curve ◽  
Density Wave Theory ◽  
Spiral Arm

Rotation curves of high luminosity spiral galaxies are flat, to distances as great as r=49 kpc. This implies a significant mass at large r. Rotational velocities increase about 20 km/s across a spiral arm, as predicted by the density wave theory. By analogy, it is suggested that our Galaxy has a flat rotation curve out to r∼60 kpc, with V ∼ constant at near the solar rotational velocity, and m ∼7×1011 m⊙. Values of A and B imply that the sun is not located in a spiral arm.

Sign in / Sign up

Export Citation Format

Share Document