Glast Dark Matter Search

The GLAST Large Area Telescope [1], scheduled for launch in 2006, is a next generation space based gamma ray telescope which will improve in point source sensitivity by a factor of 30 over that of EGRET [2] below 10 GeV, and extend beyond EGRET up to 300 GeV. Thus GLAST offers a unique opportunity to discover WIMP dark matter through precision studies of gamma rays produced in pair annihilations. The most dense region of dark matter in our galaxy is currently thought to occur at the center; in particular, dark matter should concentrate within 3 pc of the putative supermassive black hole located at the SgrA* radio source [3]. In fact, the 2nd and 3rd EGRET catalogs contain a significant point source coincident with the Milky Way galactic center within a resolution of 12 arcminutes [4]. The EGRET team has determined that the spectral and temporal characteristics of this point source are consistent with dark matter WIMP annihilations. More detailed analysis [5] has determined that the magnitude and spectrum of the EGRET source is consistent with relic WIMPs concentrated within 3 pc of the central supermassive black hole. Furthermore, the SgrA* radio emission is consistent with the synchrotron radiation expected from electrons and positrons produced in WIMP annihilations. If true, then GLAST should be able to constrain the particle properties of the postulated WIMP with 1 month of data. The accretion of a collisionless collection of non-relativistic identical particles with asymptotic velocity v0 onto a central star of mass M was first examined by Zel’dovich and Novikov [6]. In particular, we can define a critical radius