Probing the Galactic Dark matter mass function using microlensing and direct searches

Abstract

If compact baryonic objects contribute significantly to the dark matter in our Galaxy, their mass function will present vital clues for galaxy formation theories and star formation processes in the early Universe. Here we discuss what one might expect to learn about the mass function of Galactic dark matter from microlensing and from direct searches in the infrared and optical wavebands. Current microlensing results from the EROS collaboration already constrain halo mass functions which extend below 10 −4 M bd , whilst recent HST observations place strong constraints on disc and halo dark matter mass functions extending above 0.1 M ⊙ . Infrared observations should either detect or constrain objects larger than 0.01 M ⊙ in the near future. Objects below 0.01 M ⊙ should be detectable through microlensing, although the prospects of determining their mass function depend critically on a number of factors.