Gary Mamon's Research Topics: Mass and Orbits

Global mass measurements of cosmic structures indicate that dark matter comprises roughly 85% of the mass density of the Universe. One of the fundamental goals of astrophysics is to measure the radial distribution of dark matter in astronomical structures, because:

  1. It serves as a reference to compare the observed distributions of stars, gas, dust, metals, etc.
  2. These measurements can be compared to the predictions from cosmological N-body simulations without or with gas, providing a useful test on the standard cosmological model.

Gary Mamon has developed new mathematical algorithms to determine the radial distribution of the total mass of near-spherical astronomical systems (clusters and groups of galaxies, as well as elliptical galaxies, dwarf spheroidal galaxies and globular clusters), from their internal motions. His algorithms are applied to observations of the projected distances of the constituents to the system's center as well as to their line-of-sight velocities (line-of-sight distances [depth] and plane-of-sky velocities are rarely available). The Jeans equations of local dynamical equilibrium can be used, but they need to be combined with projection equations to relate to observational quantities and, worse, they include a degeneracy between the unknown radial profiles of total mass and velocity anisotropy (which measures the shapes of the orbits from radial to circular).

More precisely, Gary Mamon has developed algorithms for

Gary Mamon's important papers on the topic are: