Dark Matter in Galaxies: Evidences and Challenges

Abstract

The evidence of the phenomenon for which, in galaxies, the gravitating mass is distributed differently than the luminous mass, increases as new data become available. Furthermore, this discrepancy is well structured and it depends on the magnitude and the compactness of the galaxy and on the radius, in units of its luminous size R opt , where the measure is performed. For the disk systems with −13 ≥ M I ≥ −24 all this leads to an amazing scenario, revealed by the investigation of individual and coadded rotation curves, according to which, the circular velocity follows, from their centers out to their virial radii, an universal profile V U RC (r/R opt , M I ) function only of the properties of the luminous mass component. Moreover, from the Universal Rotation Curve, so as from many individual high quality RCs, we discover that, in the innermost regions of galaxies, the DM halo density profiles are very shallow. Finally, the disk mass, the central halo density and its core radius, come out all related to each other and to two properties of the distribution of light in galaxies: the luminosity and the compactness. This phenomenology, being absent in the simplest ΛCDM Cosmology scenario, poses serious challenges to the latter or, alternatively, it requires a substantial and tuned involvement of baryons in the formation of the galactic halos. On the other side, the URC helps to explain the two-accelerations relationship found by McGaugh et al 2016, in terms of only well known astrophysical processes, acting in a standard DM halos + luminous disks scenario.

Investigation of Different Dark Matter Profiles

“…If we took into account the inner structure of galaxies as in Ref. [14] and constituents of the matter as in Ref [15], probably the fits would be much better than the ones presented in this work.…”

Solar Extreme UV radiation and quark nugget dark matter model

“…In particular, in ref. [59] it has been argued that the observed correlations between the dark and luminous components is very hard to explain in a conventional dark matter scenario. Our original comment here is that the AQN dark matter model is a natural candidate which is, in principle, capable to resolve these puzzles as the nuggets are actually made of strongly interacting quarks and gluons.…”

Fundamental Properties of the Dark and the Luminous Matter from the Low Surface Brightness Discs

“…Outside r 0 the Burkert profile converges to the NFW one, this could be explained by the fact that, in the external regions of galaxies, the distances among particles are so large that the DM halos are, on a Hubble time, collisionless also if the individual particle are not. Remarkably, the Burkert profile well reproduces, in cooperation with the velocity components of the luminous matter, the individual and stacked circular velocities of spirals, dwarf disks, and of a number of ellipticals (see [30,167,168]).…”

“…A detailed description of the photometric properties of LSBs can be found in [149,191,204,206] and a suitable comparison with the same properties in HSB galaxies is made in [204]. (points with errorbars) and their best fit (solid line) alongside with the same best fit in spirals (dashed line) and dwarf disks (triangle) [30,167]). (bottom): stellar disc mass vs. the optical velocity.…”