Prospects for the Lensing of Supernovae

Observations of high redshift type Ia supernovae (SNe) will enable us to probe the structure of galaxy halos and the composition of dark matter. The future prospects for this field are briefly discussed here. First the ability of SN observations to differentiate between dark matter made of macroscopic compact objects and dark matter made of microscopic particles is reviewed. Then a new method for probing the structure of galaxy halos and galaxy cluster halos is described. This method utilizes the correlations between foreground galaxy light and supernova brightnesses to substantially decrease possible systematic errors. The technique may be particularly useful for measuring the size of dark matter halos, a measurement to which the galaxy–galaxy lensing is not well suited, and the level of substructure in galaxy halos, a problematic prediction of the cold dark matter model. The required observations of hundreds of SNe at z ∼ 1 are already being proposed for the purposes of cosmological parameter estimation.