Monday, April 03, 2017

Zwicky paradox and models of galactic dark matter

The anomalies of the halo model of dark matter have begun to accumulate rapidly. The problems of the halo model are discussed in detail in the blog "Dark matter crisis" of Prof. Pavel Kroupa and Marcel S. Pawlowski (see this). MOND is the most well-known competitor of the halo model for dark matter but has its own problems. TGD is less known alternative for the halo model. In the following brief comments about Zwicky paradox (see this) implying that neither cold nor warm dark matter particles in the usual sense (different from that in TGD based model) can play a significant role in cosmology.

The standard/concordance model of dark matter relies on two hypothesis formulated originally by Zwicky assuming that a) GRT is correct in all scales and b) all matter is created during Big Bang. Zwicky formulated two hypothesis (for references see the article) leading to the halo model of dark matter and also to Zwicky paradox.

  1. Zwicky noticed (1937) that galaxies must about 500 heavier in the Coma galaxy cluster than judged from their light emission: cold or hot dark matter halo must exist. Note that this does not actually require that the dark matter consists of some exotic particles or that the dark matter forms halos. To get historical perspective note that Vera Rubin published 1976 an article about the constancy of velocity curves for distant stars for Andromeda which is spiral galaxy.

  2. Zwicky noticed (1956) that when galaxies collide, the expelled matter can condense in new regions and form new smaller dwarf galaxies. These so called tidal galaxies are thus formed from the collisional debris of other galaxies.

From these observations one ends up with a computer model allowing to simulate the formation of galaxies (for a detailed discussion see this). The basic elements of the model are collisions of galaxies possibly leading to a fusion and formation of tidal galaxies. The model assumes a statistical distribution of dark matter lumps defining the halos of the dwarf galaxies formed in the process.

The model predicts a lot of dark matter dominated dwarf galaxies formed around the dark matter lumps: velocity spectrum should approach constant. There are also tidal dwarf galaxies formed from collision debris of other galaxies. Unless also now condensation around a dark matter lump is involved, these should not contain dark matter and velocity spectrum for tidal dwarfs should be declining. It turns out that tidal dwarfs alone are able to explain the observed dwarf galaxies, which are typically elliptic. Furthermore, there is no empirical manner to distinguish between tidal dwarfs and other dwarfs.

Do the elliptic galaxies contain dark matter? What does one know about the rotation curves of elliptic galaxies? There is an article "The rotation curves of elliptic galaxies" of J. Binney published around 1979 about the determination of the rotation curves of elliptic galaxies giving also some applications (see this). The velocity curves are declining as if no dark matter were present. Therefore dark matter would not be present in dwarf galaxies so that the prediction of the halo model would be wrong.

Could this finding be also a problem for MOND? Assuming that the laws governing gravitation are modified for small accelerations, shouldn't elliptic and spiral galaxies have similar velocity curves?

What about TGD?

  1. In TGD Universe dark energy and matter reside at flux tubes along which disk galaxies condense like pearls in string.

  2. The observation about velocity curves suggests a TGD based explanation for the difference between elliptic and spiral galaxies. Elliptic galaxies - in particular tidal dwarfs - are not associated with a flux tube containing dark matter. Spiral galaxy can form as elliptic galaxy if it becomes bound with flux tube as the recent finding about declining velocity curves for galaxies with age about 10 Gy suggest. Dark matter would not be present in dwarf galaxies so that the prediction of the halo model is wrong. This also conforms with the fact that the stars in elliptic galaxies are much older than in spiral galaxies (see this).

  3. Dwarf galaxies produced from the collision debris contain only ordinary matter. Elliptic galaxies can later condense around magnetic flux tubes so that velocity spectrum approaches constant at large distances. The breaking of spherical symmetry to cylindrical symmetry might allow to understand why the oblate spheroidal shape is flattened to that of disk.

For a summary of earlier postings see Latest progress in TGD.

Articles and other material related to TGD.


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