The mass distribution in Spiral galaxies

In the past years a wealth of observations has allowed us to unravel the structural properties of the Dark and Luminous mass distribution in spirals. As result, it has been found that their rotation curves follow, out their virial radius, an Universal function (URC) made by two terms: one due to the gravitational potential of a Freeman stellar disk and the other due to that of a dark halo. The importance of the latter is found to decrease with galaxy mass. Individual objects reveal in detail that dark halos have a density core, whose size correlates with its central value. These properties will guide $\Lambda$CDM Cosmology to evolve to match the challenge that observations presently pose.Comment: 10 pages, Invited review for IAU Symposium 244, Dark Galaxies & Lost Baryons. Typos corrected. Comments are welcom

Universal properties in galaxies and cored Dark Matter profiles

In this paper I report the highlights of the talk: "Universal properties in galaxies and cored Dark Matter profiles", given at: Colloquium Lectures, Ecole Internationale d'Astrophysique Daniel Chalonge. The 14th Paris Cosmology Colloquium 2010 "The Standard Model of the Universe: Theory and Observations"

Testing MOND with Local Group spiral galaxies

The rotation curves and the relative mass distributions of the two nearby Local Group spiral galaxies, M31 and M33, show discrepancies with Modified Newtonian dynamic (MOND) predictions. In M33 the discrepancy lies in the kinematics of the outermost regions. It can be alleviated by adopting tilted ring models compatible with the 21-cm datacube but different from the one that best fits the data. In M31 MOND fails to fit the falling part of the rotation curve at intermediate radii, before the curve flattens out in the outermost regions. Newtonian dynamics in a framework of a stellar disc embedded in a dark halo can explain the complex rotation curve profiles of these two galaxies, while MOND has some difficulties. However, given the present uncertainties in the kinematics of these nearby galaxies, we cannot address the success or failure of MOND theory in a definite way. More sensitive and extended observations around the critical regions, suggested by MOND fits discussed in this paper, may lead to a definite conclusion.Comment: 6 pages, 4 figures. To be published in MNRA

Dark Matter and MOOCs

To teach the topic of Dark Matter in Galaxies to undergraduate and PhD students is not easy, one reason being that the scientific community has not converged yet to a generally shared knowledge. We argue that the teaching of this topic and its subsequent scientific progress may benefit by Massive Online and Open Courses. The reader of this paper can express his/her opinion on this by means of a confidence vote at: https://moocfellowship.org/submissions/dark-matter-in-galaxies-the-last-mysteryComment: 2 Pages, Coments Welcom

The Extended Rotation Curve and the Dark Matter Halo of M33

We present the 21-cm rotation curve of the nearby galaxy M33 out to a galactocentric distance of 16 kpc (13 disk scale-lengths). The rotation curve keeps rising out to the last measured point and implies a dark halo mass larger than 5 10^{10} solar masses. The stellar and gaseous disks provide virtually equal contributions to the galaxy gravitational potential at large galactocentric radii but no obvious correlation is found between the radial distribution of dark matter and the distribution of stars or gas. Results of the best fit to the mass distribution in M33 picture a dark halo which controls the gravitational potential from 3 kpc outward, with a matter density which decreases radially as R^{-1.3}. The density profile is consistent with the theoretical predictions for structure formation in hierarchical clustering cold dark matter models but mass concentrations are lower than those expected in the standard cosmogony.Comment: 11 pages, 10 figures, MNRAS latex style, accepted by MNRA

Analysis of Rotation Curves in the Framework of the Gravitational Suppression Model

We present an analysis of suitable rotation curves (RCs) of eight galaxies, aimed at checking the consistency and universality of the gravitational suppression (GraS) hypothesis, a phenomenological model for a new interaction between dark matter and baryons. Motivated by the puzzle of the core versus cusp distribution of dark matter in the center of halos, this hypothesis claims to reconcile the predictions from N-body \Lambda cold dark matter simulations with kinematic observations. The GraS model improves the kinematic fitting residuals, but the mass parameters are unphysical and put the theory in difficulty.Comment: 4 pages, 3 figures, 1 tabl

The constant density region of the dark halos of spiral galaxies

From the kinematics of 137 spirals we find that the DM halo density profiles are self-similar at least out to R_opt and show core radii much larger that the corresponding disk scale-lenghts. The luminous regions of spirals consist of stellar disks embedded in dark halos with roughly constant density. With respect to previous work, the present evidence is obtained by means of a robust method and for a large and complete sample of normal spirals.Comment: 12 pages, 4 figures. MNRAS accepte