Stellar halos in normal galaxies are formed inside-out by accretion and disruption of dwarf satellites. Due to the long orbital time scales at large distances from the centre, the halos contain a fossil record of galaxy assembly and show a rich substructure. Current simulations are able to explain many of the features observed, yet certain mysteries remain. In recent years it has become evident that the optical/near-IR colours of some halos have extremely red colours that strongly deviate from predictions of colours of normal stellar populations. I will review some of the observational support for the red colour excess and focus on a recent study of Low Surface Brightness Galaxies, based on stacked g-r-i images from the Sloan Digital Sky Survey. Although we find no satisfactory explanation of the red excess I will discuss mechanisms that give predictions marginally consistent with the observations.
2009 November 19, 13:30
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto