A "Universal" Density Profile for the Outer Stellar Halos of Galaxies

Understand

The outer stellar halos of galaxies contain vital information about the formation history of galaxies, since the relaxation timescales in the outskirts are long enough to keep the memory, while the information about individual formation events in the central parts has long been lost due to mixing, star formation and relaxation.

• To unveil some of the information encoded in these faint outer halo regions, we study the stellar outskirts of galaxies selected from a fully hydrodynamical high resolution cosmological simulation, called Magneticum.
• We find that the density profiles of the outer stellar halos of galaxies over a broad mass range can be well described by an Einasto profile.
• For a fixed total mass range, the free parameters of the Einasto fits are closely correlated.