Nature and distribution of dark matter: 2. binaries,groups and clusters |
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| Authors: | M M Vasanthi T Padmanabhan |
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| Institution: | (1) 705, ‘Raman’,TIFR HousingColony, Homi Bhabha Road, 400005 Bombay;(2) Astrophysics Group, Tata Institute of Fundamental Research, Homi Bhabha Road, 400005 Bombay |
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| Abstract: | We study the mass-radius relationship for aggregates of galaxies, viz. binaries, small groups and clusters. The data are subjected
to a simple best-fit analysis similar to the one carried out earlier for individual field galaxies. The analysis shows that:
(i) The data on binary galaxies are consistent with the assumption that binaries are just two galaxies, each with an individual
isothermal (M ∫R) dark matter halo, moving under the mutual gravitational attraction, (ii) The data on the groups of galaxies are too scattered
to obey a single power-law relation of the formM = kR
n
with any degree of reliability, (iii) The data on groups and clusters fit better with a law of the formM = AR
3
+BR. This form suggests the existence of two components in dark matter—one which is clustered around the galaxies (M ∫R) and another which is distributed smoothly (M ∫R
3
). The smooth distributions becomes significant only at scales ≥ 1 Mpc and hence does not affect binaries significantly. We
briefly discuss the theoretical implications of this analysis |
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| Keywords: | galaxies dark matter galaxies binary galaxies clusters |
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