Document Type : Original Article
Authors
Faculty of Physics, Department of Fundamental Physics, University of Alzahra, Tehran, Iran
Abstract
A spherically symmetric matter collapses under its own gravity. For the Milky Way, the time scale of collapse for a spherical halo with NFW density is ∼ 26 My which is very small compared to the age of the Milky Way. The effect of a pressure, obeying a polytrope equation of state is investigated. It is shown that for p ∝ ρ9/8, the time scale would be of the order of 1 Gy. It is also argued that such a polytrope, if considered to be in equilibrium, could explain the rotation curve of the milky way.
Keywords
Main Subjects
- A Dekel, F Stoehr, G A Mamon, T J Cox, G S Novak, and J R Primack, Nature 437 (2005) 7059.
- B Famaey and SMcGaugh, Living Rev. 15 (2012) 10.
- L M Fern´andez -Hern´andez, M A Rodr´ıgues -Meza, and T Matos, Phys. Conf. Ser. 1010 (2018) 12005.
- Christian Knobel,. arXiv, 1208 (2013) 5931v2.
- E L Lokas and G A Mamon. Monthly Notices of the Royal Astronomical Society 343 (2003) 2.
- R Massey, T Kitching and J Richard, The dark matter of gravitational lensing. Reports on Progress in Physics 73 (2010) 086901.
- Eckehard W Mielke and Franz E Schunck, Rev. D 66 (2002) 023503.
- J F Navarro, C S Frenk, and S D M White. The Astrophysical Journal 462 (1996) 563.
- Y Sofue, “Rotation and mass in the Milky Way and spiral galaxies”. Publications of the Astronomical Society of Japan, 69 1 (2017).
- Y Sofue, Galaxies 8 (2020) 2.
- A M Wazwas, Mathematics and Computation 118 (2001) 287.
- S Weinberg, Gravitation and Cosmology: “Principles and applications of the general theory of relativity”, John Wiley & Sons (1972).
- S Weinberg, “Cosmology”, Oxford Unversity Press (2008).
)