Wednesday, April 05, 2017

Missing dark matter

One problem of ΛCDM scenario is missing of matter and dark matter in some places (see this). There missing dark matter in the scale of R=.2 Gy and also in the vicinity of solar system in the scale 1.5-4 kpc.

In the work titled "Missing Dark Matter in the Local Universe", Igor D. Karachentsev studied a sample of 11,000 galaxies in the local Universe around the MW (see this). He summed up the masses of individual galaxies and galaxy-groups and used this to test a very fundamental prediction of ΛCDM.

  1. Standard cosmology predicts the average fraction of matter density to be Ωm,glob=28+/- 3 per cent of critical mass density (83 percent of this would be dark and 17 per cent visible matter). 72 per cent would be dark energy, 28 per cent dark matter, and 4.8 per cent visible matter.

    To test this one can simply sum up all the galactic masses in some volume Karachentsev chose the volume to be a sphere of radius R= .2 Gy surrounding Milky Way and containing 11,000 galaxies. In this scale the density is expected to fluctuate only 10 per cent. Note that horizon radius is estimated to be about RH=14 Gly giving RH= 70 R.

  2. The visible galactic mass in certain large enough volume of space was estimated as also the sum of galactic dark masses estimated as so called virial mass (see this). The sum of these masses gave the estimate for the total mass.

  3. The estimate for the total mass (dark matter plus visible matter assuming halo model) in a volume of radius .2 Gy gives Ωm,glob=8+/- 3 per cent, which is only 28 per cent of the predicted fraction. The predicted fraction of visible matter is 4.8 per cent and marginally consistent with 8+/- 3 per cent but it seems plausible that also dark matter is present although its amount is much smaller than expected. The total contribution to the dark matter could be at most of the same size as that of visible matter.

  4. One explanation is that all matter has not been included. Second not very plausible explanation is that the measurement region corresponds to a region with abnormally low density.

Can on understand the finding in TGD framework?
  1. In TGD based model part of dark energy/matter would reside at the long flux tubes with which galaxies form bound states. Constraints come from accelerated expansion and galactic velocity curves allowing to determine string tension for given galaxy. Let us assume that the GRT limit of TGD and its predictions hold true.

    The estimate for the virial mass assumes that galaxy's dark mass forms a halo. The basic observation is that in TGD flux tubes give the dark energy and mass and virial mass would underestimate the the dark mass of the galaxy.

  2. How long length of the flux tube effectively corresponds to the dark and visible mass of disk galaxy? This length should be roughly the length containing the dark mass and energy estimated from cosmology: L=Mdark/T. If GRT limit of TGD makes sense, one has Mdark =xMvis/T, where Mdark is the amount of dark energy + matter associated with the flux tube, Mvis is visible mass, x≈ ρdarkvis≈ 83/17 , and T is string tension deduced from the asymptotic rotation velocity.

    If these segments do not cover the entire flux tubes containing the galaxies along it, the amount of dark matter and energy will be underestimated. By the above argument elliptic galaxies would not have considerable amount of dark matter and energy so that only disk galaxies should contribute unless there are flux tubes in shorter scales inside elliptic galaxies.

    Also larger and smaller scale flux tube structures contribute to the dark energy + dark matter. Fractality suggests the presence of both larger and smaller flux tube structures than those associated with spiral galaxies (even stars couldbe associated with flux tubes).

    One should have estimates for the lengths of various flux tubes involved. Unfortunately this kind of estimate is not available.

  3. If GRT limit makes sense then the total dark mass then the dark energy and matter obtained in this manner should give 95 per cent of critical mass density. The fraction of dark matter included would be at most a fraction 5/28≈ 18 per cent of the total dark matter. 82 per cent of dark matter and energy would be missed in the estimate. This could allow to get some idea about the lengths of flux tubes and density of galaxies along flux tubes.

The amount of dark matter in the solar neighborhood was investigated in the work "Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood" by Christian Moni Bidin and collaborators (see this). Moni Bidin et al have studied as sample of 400 red giants in the vicinity of solar system at vertical distances 1.5 to 4 kpc and deduce 3-D kinematics for these start. From this data they estimate the surface mass density of the Milky Way within this range of heights from the disk. This surface density should be sum of both visual and dark mass.

According to their analysis, the visible mass is enough to explain the data. No additional mass is needed. Only highly flattened dark matter halo would be consistent with the findings. This conforms with the TGD prediction that dark mass/energy are associated with magnetic flux tubes.

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

Articles and other material related to TGD.


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