For 10 points, name these spherical regions surrounding galaxies that are filled with dark matter.
The number density of these objects at a particular mass is calculated by the excursion set method, which is a modification of the Press-Schechter formalism. That method is in turn used to create merger trees of these. Methods of finding these entities in simulations include the Friends-of-Friends algorithm and the bound-density maximum method. The masses of these entities can be estimated from stellar luminosity in a type of abundance matching named for these entities. One problem in the modelling of these objects is that simulations of them show high density at the center; that problem calls these entities "cuspy". The mass distribution of these entities can be estimated via the exponential Einasto profile and the (*) NFW profile. These entities serve as seed points for baryonic matter and are thus the building blocks of hierarchical structure formation. MACHOs are named for the fact that they exist in these regions, and these regions were hypothesized after Rubin found that rotation curves aren't Keplerian. For 10 points, name these spherical regions surrounding galaxies that are filled with dark matter.
The number density of these objects at a particular mass is calculated by the excursion set method, which is a modification of the Press-Schechter formalism.
dark matter halo [prompt on “galaxies” or “galaxy seeds”]