COMPLEXITY ON DWARF GALAXY SCALES: A BIMODAL DISTRIBUTION FUNCTION IN SCULPTOR

摘要

In our previous work, we presented Schwarzschild models of the Sculptor dwarf spheroidal galaxy demonstrating that this system could be embedded in dark matter halos that are either cusped or cored. Here, we show that the non-parametric distribution function recovered through Schwarzschild’s method is bimodal in energy and angular momentum space for all of the best-fitting mass models explored. We demonstrate that this bimodality is directly related to the two components known to be present in Sculptor through stellar population analysis, although our method is purely dynamical in nature and does not use this prior information. It therefore constitutes independent confirmation of the existence of two physically distinct dynamical components in Sculptor and suggests a rather complex assembly history for this dwarf galaxy.