We apply the concept of spiral rotation curves universality [1] in order to investigate the properties of the baryonic and dark matter components of low surface brightness galaxies (LSB). The sample is composed by 72 objects, whose rotation curves are selected from literature. After a galaxies' division in five velocity bins according to their increasing optical velocity, we observe that in specifically normalized units the rotation curves are all alike in each selected velocity bin, i.e. it reflects the idea of the universal rotation curve (URC) found in Persic et al. [1]. From the mass modeling of our galaxies, we show that the dark matter component is dominant rather than the baryonic one, especially within the smallest and less luminous LSB galaxies. The Burkert profile results to be an optimal model fit for the dark matter halos and it is shown that the central surface density Σ0 ∼ 100 M pc −2 , similar to galaxies of different Hubble types and luminosities. Our analysis leads to a strong correlation between the structural properties of the dark and luminous matter. In particular, when we also evaluate the compactness for stars and dark matter, a strong correlation emerges between the stellar disc and dark matter halo. Finally, the introduction of the stellar compactness C * as a new parameter in the ballpark of the luminous matter besides the optical radius and the optical velocity improves the URC.

We reconsider the lower bound on the mass of a fermionic dark matter (DM) candidate resulting from the existence of known small Dwarf Spheroidal galaxies, in the hypothesis that their DM halo is constituted by degenerate fermions, with phase-space density limited by the Pauli exclusion principle. By relaxing the common assumption that the DM halo scale radius is tied to that of the luminous stellar component and by marginalizing on the unknown stellar velocity dispersion anisotropy, we prove that observations lead to rather weak constraints on the DM mass, that could be as low as tens of eV. In this scenario, however, the DM halos would be quite large and massive, so that a bound stems from the requirement that the time of orbital decay due to dynamical friction in the hosting Milky Way DM halo is longer than their lifetime. The smallest and nearest satellites Segue I and Willman I lead to a final lower bound of m 100 eV, still weaker than previous estimates but robust and independent on the model of DM formation and decoupling. We thus show that phase space constraints do not rule out the possibility of sub-keV fermionic DM.to Giulia D.S.

McGaugh et al. (2016) have found, in a large sample of disc systems, a tight nonlinear relationship between the total radial accelerations g and their components g b arisen from the distribution of the baryonic matter . Here, we investigate the existence of such relation in Dwarf Disc Spirals and Low Surface Brightness galaxies on the basis of Karukes & Salucci (2017) and Di Paolo & Salucci (2018). We have accurate mass profiles for 36 Dwarf Disc Spirals and 72 LSB galaxies. These galaxies have accelerations that cover the McGaugh range but also reach out to one order of magnitude below the smallest accelerations present in McGaugh et al. (2016) and span different Hubble Types. We found, in our samples, that the g vs g b relation has a very different profile and also other intrinsic novel properties, among those, the dependence on a second variable: the galactic radius, normalised to the optical radius R opt , at which the two accelerations are measured. We show that the new far than trivial g vs (g b , r/R opt ) relationship is nothing else than a direct consequence of the complex, but coordinated mass distributions of the baryons and the dark matter (DM) in disc systems. Our analysis shows that the McGaugh et al. (2016) relation is a limiting case of a new universal relation that can be very well framed in the standard "DM halo in the Newtonian Gravity" paradigm.

In Cosmology and in Fundamental Physics there is a crucial question like: where the elusive substance that we call Dark Matter is hidden in the Universe and what is it made of? that, even after 40 years from the Vera Rubin seminal discovery [1] does not have a proper answer. Actually, the more we have investigated, the more this issue has become strongly entangled with aspects that go beyond the established Quantum Physics, the Standard Model of Elementary particles and the General Relativity and related to processes like the Inflation, the accelerated expansion of the Universe and High Energy Phenomena around compact objects. Even Quantum Gravity and very exotic Dark Matter particle candidates may play a role in framing the Dark Matter mystery that seems to be accomplice of new unknown Physics. Observations and experiments have clearly indicated that the above phenomenon cannot be considered as already theoretically framed, as hoped for decades. The Special Topic to which this review belongs wants to penetrate this newly realized mystery from different angles, including that of a contamination of different fields of Physics apparently unrelated. We show with the works of this ST that this contamination is able to guide us into the required new Physics. This review wants to provide a good number of these “paths or contamination” beyond/among the three worlds above; in most of the cases, the results presented here open a direct link with the multi-scale dark matter phenomenon, enlightening some of its important aspects. Also in the remaining cases, possible interesting contacts emerges. Finally, a very complete and accurate bibliography is provided to help the reader in navigating all these issues.

Well known scaling laws among the structural properties of the dark and the luminous matter in disc systems are too complex to be arisen by two inert components that just share the same gravitational field. This brings us to critically focus on the 30-year-old paradigm, that, resting on a priori knowledge of the nature of Dark Matter (DM), has led us to a restricted number of scenarios, especially favouring the collisionless Λ Cold Dark Matter one. Motivated by such observational evidence, we propose to resolve the dark matter mystery by following a new Paradigm: the nature of DM must be guessed/derived by deeply analyzing the properties of the dark and luminous mass distribution at galactic scales. The immediate application of this paradigm leads us to propose the existence of a direct interaction between Dark and Standard Model particles, which has finely shaped the inner regions of galaxies.