Related papers: Why do galaxies have extended flat rotation curves…
A population of discrete HI clouds in the halo of the inner Galaxy has been discovered in 21cm observations made with the Green Bank Telescope. The halo clouds are seen up to 1.5 kpc from the Galactic plane at many longitudes. Their…
The late infall of dark matter onto a galaxy produces structure (such as caustics) in the distribution of dark matter in the halo. We argue that such structure is likely to occur generically on length scales proportional to $l \sim t_0…
High resolution N-body simulations of galactic cold dark matter haloes indicate that we should expect to find a few satellite galaxies around the Milky Way whose haloes have a maximum circular velocity in excess of 40 kms. Yet, with the…
It is suggested that the recently observed size evolution of very massive compact galaxies in the early universe can be explained, if dark matter is in Bose Einstein condensate. In this model the size of the dark matter halos and galaxies…
On the basis of a recent cosmological model, the puzzle of galactic rotational velocities at their edges is explained without invoking dark matter. A rationale for the existence of structures like galaxies and superclusters is also…
Observations of the nearby large galaxies that can be examined in particularly close detail suggest that many have small stellar luminosity fractions in bulges and haloes. Simulations of galaxy formation tend to produce considerably larger…
Lopsidedness is a common feature in galaxies, both in the distribution of light and in the kinematics. We investigate the kinematics of a model for lopsided galaxies that consists of a disc lying off-centre in a dark halo, and circling…
If dark matter is dissipative then the distribution of dark matter within galactic halos can be governed by dissipation, heating and hydrostatic equilibrium. Previous work has shown that a specific model, in the framework of mirror dark…
The rotation curves of disk galaxies exhibit a number of striking regularities. The amplitude of the rotation is correlated with luminosity (Tully-Fisher), the shape of the rotation curve is well predicted by the luminous mass distribution,…
We present decompositions of the rotation curves of distant spiral galaxies into contributions due to their bulges, disks, and putative dark haloes. In order to set constraints on the ambiguities of the decompositions we interpret the…
It has been proposed that the flat rotation curves observed at large radii in disk galaxies can be interpreted as an effect of General Relativity (GR) instead of the presence of dark matter (DM) halos in Newtonian gravity. In Ciotti (2022)…
The gas temperature in the cores of many clusters of galaxies drops inward by about a factor of three or more within the central 100kpc radius. The radiative cooling time drops over the same region from 5 or more Gyr down to about 10^8 yr.…
We present a spherically symmetric model for the origin and evolution of the temperature profiles in the hot plasma filling galaxy groups and clusters. We find that the gas in clusters is generically not isothermal, and that the temperature…
Clusters of galaxies, filled with hot magnetized plasma, are the largest bound objects in existence and an important touchstone in understanding the formation of structures in our Universe. In such clusters, thermal conduction follows field…
A large class of flat axially symmetric solutions to the Vlasov-Poisson system is constructed with the property that the corresponding rotation curves are approximately flat, slightly decreasing or slightly increasing. The rotation curves…
A galactic disk in a spiral galaxy is generally believed to be embedded in an extended dark matter halo, which dominates its dynamics in the outer parts. However, the shape of the halo is not clearly understood. Here we show that the dark…
Knowledge of the shape of dark matter halos is critical to our understanding of galaxy formation, dynamics, and of the nature of dark matter itself. Polar ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of gas,…
Lenticular galaxies are generally thought to have descended from spirals via morphological transformation, although recent numerical simulations have shown that minor or even major merger can also lead to an S0-like remnant. These…
The rotation curves of 20 spiral galaxies are examined in the light of a toy model (Soares 1992) which has as the main feature the assignment of a high M/L ratio (=30; Ho=50 km/s/Mpc) to the visible matter. The observed rotation of all…
Higher order curvature gravity has recently received a lot of attention due to the fact that it gives rise to cosmological models which seem capable of solving dark energy and quintessence issues without using "ad hoc" scalar fields. In…