Dark matter in galaxies

Abstract

Dark matter in galaxies, its abundance, and its distribution remain a subject of long-standing discussion, especially in view of the fact that neither dark matter particles nor dark matter bodies have yet been found. Experts' opinions range from a very large number of completely dark galaxies exist to nonbaryonic dark matter does not exist at all in any significant amounts. We discuss astronomical evidence for the existence of dark matter and its connection with visible matter and examine attempts to estimate its mass and distribution in galaxies from photometry, dynamics, gravitational lensing, and other observations (the cosmological aspects of the existence of dark matter are not considered in this review). In our view, the presence of dark matter in and around galaxies is a well-established fact. We conclude with an overview of mechanisms by which a dark halo can influence intragalactic processes.Comment: 82 pages, 35 figure

What made discy galaxies giant?

“…The relation between the virial halo mass and the disc mass for a sample of discy galaxies was demonstrated e.g. in Zasov et al (2017). As far as stellar mass is connected to the size of the disc it is natural to expect that the latter is also related to the halo mass.…”

Scattering of high-energy cosmic ray electrons off the Dark Matter

“…It seems reasonable to consider the processes of interaction of cosmic ray fluxes with the DM particles [13][14][15][16] forming the halo of the Galaxy. [17][18][19] Indeed, such analysis can be useful to detect some peculiar signals that differ in energy spectrum or spatial distributions from the annihilation signals of the DM. More specifically, we calculate here cross section of cosmic electron interaction with hyperpions (Hpions), which are the one of two DM component in vectorlike hypercolor extension of the Standard Model.…”

“…32: λ i = 2.76 × 10 35 mπ < σv > i (m is in GeV and < σv > in cm 3 s −1 ) and Y eq π = 0.145(3/g(T ))x 3/2 e −x , Y eq B = 0.145(2/g(T ))x 3/2 e −x , g(T ) is the number b We neglect terms ∆Mπ/M B due to the small mass splitting between neutral components of the DM.of relativistic degrees of freedom contributing to the energy density c . Note that the function g(T ) can be effectively approximated as: log 10 T + 0.5)] + 10 tanh [3 (log 10 T − 1.65)] ,(18)…”

A Numerical Simulation of the Shallow Water Flow on a Complex Topography

“…It should be noted that the SWM is also actively applied and developed for theoretical research of various cosmic gas flows. The shallow water approximation allows describing a whole series of astrophysical objects: the protoplanetary and circumstellar disks [10,11], the accretion disks around the compact relativistic objects [12], the cyclonic movements in the giant planets' atmospheres [13], and the spiral galaxies gas disk components [14]. The gravitational fields play the topography role in such astrophysical problems.…”