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Description
The existence of dynamically relaxed stellar density cusp in dense clusters around massive black holes is a long-standing prediction of stellar dynamics, but it has so far escaped unambiguous observational confirmation. In this paper we revisit the problem of inferring the innermost structure of the Milky Way's nuclear star cluster via star counts, to clarify whether it displays a core or a cusp around the central black hole. We use judiciously selected adaptive optics assisted high angular resolution images obtained with the NACO instrument at the ESO VLT. Through image stacking and improved PSF fitting we push the completeness limit about one magnitude deeper than in previous, comparable work. Crowding and extinction corrections are derived and applied to the surface density estimates. Known young, and therefore dynamically not relaxed stars, are excluded from the analysis. Contrary to previous work, we analyse the stellar density in well-defined magnitude ranges in order to be able to constrain stellar masses and ages. We conclude that the observed density of the faintest stars detectable with reasonable completeness at the Galactic Centre, is consistent with the existence of a stellar cusp around the Milky Way's central black hole, Sagittarius A*.
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