We consider the orbital evolution and tidal evaporation and disruption of globular clusters and dwarf spheroidal galaxies in the gravitational potential of an isothermal dark matter halo, consistent with that predicted by current observations of flat rotation curves in spiral galaxies. The rate of orbital decay due to dynamical friction and mass-loss rates including halo-induced tidal effects are computed self consistently using a semi-analytical model. A wide range of cluster masses and central mass concentrations for both circular and radial orbits was considered. We find that the high-mass clusters (M_c approx> 10~7 solar mass) suffer substantial to complete orbital decay due to dynamical friction, while the low-mass clusters (M_c approx< 10~5 solar mass) suffer substantial to complete evaporation or disruption. The mass contribution to the halo, per cluster, is small in both cases. Intermediate-mass clusters of high central mass concentration survive for a Hubble time, while intermediate and high-mass clusters of low central mass concentration evaporate or disrupt and may have contributed a large fraction of the mass in the halo. For all initial orbital sizes and cluster concentrations the mass range for surviving clusters is narrower for radial orbits, and the halo stars contributed by these clusters should have highly eccentric orbits. Our results show that the current globular cluster population is, to a large extent, consistent with that determined from our simple approximation, which considers only the gravitational effects of an isothermal halo.
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