A Prescription for Building the Milky Way's Halo from Disrupted Satellites

Abstract

We develop a semi-analytic method for determining the phase-space population\nof tidal debris along the orbit of a disrupting satellite galaxy and illustrate\nits use with a number of applications. We use this method to analyze Zhao's\nproposal that the microlensing events towards the Large Magellanic Cloud (LMC)\nmight be explained by an appropriately placed tidal streamer, and find that his\nscenarios lead either to unacceptably high overdensities (10 -- 100%) in faint\nstar counts (apparent magnitudes 17.5 -- 20.5) away from the Galactic plane or\nshort timescales for the debris to disperse (10^8 years). We predict that the\ntidal streamers from the LMC and the Sagittarius dwarf galaxy currently extend\nover more than $2\\pi$ in azimuth along their orbits. Assuming that each\nsatellite has lost half of its primordial mass, we find that the streamers will\nhave overdensities in faint star counts of 10 -- 100% and < 1% respectively,\nand conclude that this mass loss rate is unlikely for the LMC, but possible for\nSagittarius. If the Galaxy has accreted one hundred $10^5-10^6 M_{\\odot}$\nobjects (comparable to its current population of globular clusters) at\ndistances of 20 -- 100 kpc during its lifetime then 10% of the sky will now be\ncovered by tidal streamers.\n