Monday, December 5, 2022

More Ties Between Ordinary And Inferred Dark Matter

Starting from the 1970s, some relations connecting dark matter and baryons were discovered, such as the Tully-Fisher relation. However, many of the relations found in galaxies are quite different from that found in galaxy clusters. Here, we report two new mysterious universal relations connecting dark matter and baryons in both galaxies and galaxy clusters. 
The first relation indicates that the total dynamical mass of a galaxy or a galaxy cluster M(500) has a power-law relation with its total baryonic mass M(b) within the `virial region': M(500)∝M(b)^a, with a≈3/4. 
The second relation indicates that the enclosed dynamical mass M(d) is almost directly proportional to the baryonic mass for galaxies and galaxy clusters within the central baryonic region: M(d)∝M(b). 
The close relations between dark matter and baryons in both galaxies and galaxy clusters suggest that some unknown interaction or interplay except gravity might exist between dark matter and baryons.
Man Ho Chan, "Two mysterious universal dark matter-baryon relations in galaxies and galaxy clusters" arXiv:2212.01018 (December 2, 2022) (Accepted in Physics of the Dark Universe).

The second assumption is trivially true in MOND by virtue of the structure of the theory. It is also true, but less trivially, in Deur's approach, because gravitational self-interaction is a second order effect in weak gravitational fields.


neo said...

MOND fails to get galaxy clusters

andrew said...

Yes, it underestimates the amount of inferred DM in galaxy clusters (although by less than previously believed and only about 50%). But, it gets the baryon dense parts of galaxy clusters right. The part it gets wrong is strength of the weak attraction between distant galaxies in the cluster which it underestimates.

andrew said...

See M. Lopez-Corredoira, et al., "Virial theorem in clusters of galaxies with MOND" arXiv:2210.13961 (October 25, 2022) (accepted for publication in MNRAS).

neo said...

i wonder if magnet between galaxies in clusters of galaxies could explain why it underestimates the amount of inferred DM in galaxy clusters

andrew said...

Electromagnetism is almost certainly not the source of underestimates of the amount of inferred DM in galaxy clusters. We know this because electromagnetism is easily to detect with specialized telescopes which cover almost the entire frequency range of electromagnetism and because electromagnetic interactions are understood to exquisite precision (which is possible in part because photons, unlike gravitons, do not have tree level self-interactions).

Aestros said...

It could be explained by the Janus cosmological model.
I would really appreciate your expert insights into this interesting paper please:
Have a nice day