DARK MATTER

The search for non-luminous objects in the galactic halo (MACHOs) was proposed as one of the original applications of gravitational microlensing. In this applications, stars in the Magellanic Clouds are used as sources of light, and dark lenses are sought along the lines of site to these galaxies. Searches by the MACHO and EROS groups yielded upper limits to the fraction of dark matter in this form, and also some unexplained events.

The MOA group is continuing these studies, placing particular emphasis on determining the distances to the lenses. It is not known if some of the lenses for the original events lay in the galactic halo or not. It has been shown that this ambiguity may be able to be addressed in future events by concentrating specifically on those of high magnification. Further details are at astro-ph/0208399 and astro-ph/0004137 .

The cross marks the position of the Mt John Observatory.