Astrophysics

   

Spiral Galaxy Rotation Curves and Arm Formation Without Dark Matter or MOND

Authors: Tarun Biswas

Usual explanations of spiral galaxy rotation curves assume circular orbits of stars. The consequences of giving up this assumption were investigated through a couple of models in an earlier communication. Here, further investigations of one of these models (the spinner model) shows that it can explain the formation of the spiral arms as well. It is also shown that the behavior of the tail of the rotation curve is related to the age of the galaxy. The spinner model conjectures the existence of a spinning hot disk around a spherical galactic core. The disk is held together by local gravity and electromagnetic scattering forces. However, it disintegrates at the edge producing fragments that form stars. Once separated from the disk, the stars experience only the centrally directed gravitational force due to the massive core and remaining disk. A numerical simulation shows that a high enough angular velocity of the disk produces hyperbolic stellar trajectories that agree with the observed rotation curves. Besides the rotation curves, the simulation generates two other observable features of spiral galaxies. First, it shows the formation of spiral arms and their nearly equal angular separations. Second, it determines that, for large radial distances, younger galaxies have rotation curves that dip downwards and older galaxies have a rising trend. The strength of this model lies in the fact that it does not require the postulation of dark matter or MOND. This model also revisits the method of estimation of star age. As the stars are formed from an already hot disk, they do not start off as cold collections of dust and gas. Hence, their ages are expected to be significantly less than what current models estimate. This explains why they have not escaped the galaxy in spite of their hyperbolic trajectories.

Comments: 6 pages, 7 figures

Download: PDF

Submission history

[v1] 2018-11-04 21:28:47

Unique-IP document downloads: 15 times

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