The problem of the deficit of dwarf galaxies

Dwarf Galaxy NGC 1140 . ^[one]

The problem of deficiency of dwarf galaxies ( English the missing satellites problem ) arises in cosmological simulations that predict the evolution of the distribution of matter in the universe . Dark matter is likely to form hierarchical condensations, with the number of halo increasing as the size of the halo decreases. The observed distribution of ordinary galaxies in number is consistent with the simulation results, but the number of dwarf galaxies ^[2] is orders of magnitude smaller than expected from the simulation results. ^{[3] [4]} For comparison, about 38 dwarf galaxies were observed in the Local Group of galaxies (for 1998), 11 of them circled around the Milky Way ^[2] (for more modern data see the list ), but the simulation results predict the existence of order 500 dwarf satellite galaxies on the Milky Way. ^{[3] [4]}

To solve this problem, there are two main alternative models. One of them is that smaller halo do exist, but only a part of them becomes visible, because the remaining ones are not able to attract enough baryonic matter to create an observable dwarf galaxy. According to observations by the Kek Observatory, in 2007 8 ultraweak dwarf satellites of the Milky Way were discovered, 6 of which are estimated to be 99.9% dark matter ( the mass-luminosity ratio reaches 1000). ^[5] Another solution to the problem may be the assumption of the merger or tidal destruction of dwarf galaxies large with a complex interaction configuration. Tidal removal of matter is a problem for detecting dwarf galaxies, since in this case the galaxies have extremely low surface brightness and are very scattered, so they are almost impossible to observe.