A Prescription for Building the Milky Wayïs Halo from Disrupted Satellites

We develop a semianalytic method for determining the phase-space population of tidal debris along the orbit of a disrupting satellite galaxy and illustrate its use with a number of applications. We use this method to analyze ZhaoÏs proposal that the microlensing events toward the Large Magellanic Cloud (LMC) might be explained by an appropriately placed tidal streamer and Ðnd that his scenarios lead either to unacceptably high overdensities (10%È100%) in faint star counts (apparent magnitudes 17.5È20.5) away from the Galactic plane or short timescales for the debris to disperse (108 yr). We predict that the tidal streamers from the LMC and the Sagittarius dwarf galaxy currently extend over more than 2n in azimuth along their orbits. Assuming that each satellite has lost one-half of its primordial mass, we Ðnd that the streamers will have overdensities in faint star counts of 10%È100% and less than 1%, respectively, and conclude that this mass-loss rate is unlikely for the LMC but possible for Sagittarius. If the Galaxy has accreted 100 objects of 105È106 (comparable to its current M _ population of globular clusters) at distances of 20È100 kpc during its lifetime, then 10% of the sky will now be covered by tidal streamers. Subject headings : galaxies : interactions È Galaxy : evolution È Galaxy : formation È Galaxy : halo È Galaxy : kinematics and dynamics È Magellanic Clouds