EROS: a Galactic Microlensing Odyssey

Abstract

The EROS microlensing survey has monitored nearly 100 million stars for seven years, to search for halo brown dwarfs and compact objects in the Galactic disk. In this paper, we review the various EROS observation programs and the corresponding microlensing search results. In particular, based on LMC and SMC observations, EROS excludes a major contribution from compact objects with masses in the range 2. x 10^{-7} - 1 M_{\odot} to the Galactic halo. Less than 25% of the standard halo mass can be made of such objects, while the EROS measured optical depths toward the Galactic spiral arms (< tau_{SA} > \simeq 0.43 x 10^{-6}) and Galactic bulge (< tau_{GC} > \simeq 0.93 x 10^{-6}) are compatible with Galactic model predictions if the contribution from an elongated bar in the centre is taken into account.