Dark matter in galaxies

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.