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The limits of available computing power have forced models for the structureof stellar halos to adopt one or both of the following simplifying assumptions:(1) stellar mass can be "painted" onto dark matter particles in progenitorsatellites; (2) pure dark matter simulations that do not form a luminous galaxycan be used. We estimate the magnitude of the systematic errors introduced bythese assumptions using a controlled set of stellar halo models where weindependently vary whether we look at star particles or painted dark matterparticles, and whether we use a simulation in which a baryonic disk galaxyforms or a matching pure dark matter simulation that does not form a baryonicdisk. We find that the "painting" simplification reduces the halo concentrationand internal structure, predominantly because painted dark matter particleshave different kinematics than star particles even when both are buried deep inthe potential well of the satellite. The simplification of using pure darkmatter simulations reduces the concentration further, but increases theinternal structure, and results in a more prolate stellar halo. Thesedifferences can be a factor of 1.5-7 in concentration (as measured by thehalf-mass radius) and 2-7 in internal density structure. Given this level ofsystematic uncertainty, one should be wary of overinterpreting differencesbetween observations and the current generation of stellar halo models based ondark matter only simulations when such differences are less than an order ofmagnitude.

Systematic Problems With Using Dark Matter Simulations to Model Stellar Halos