Re-examining the Radial Distributions of M13 Multiple Populations

Abstract

Abstract We seek to resolve the tension in the literature regarding the presence of radially segregated multiple populations in the Galactic globular cluster M13. Previous studies of this nearby cluster have presented discordant results about the degree of dynamical mixing in M13's inner region. Using ground-based (UBVI) photometry, we show that cumulative radial distributions of stars on the blue and red sides of the red giant branch are statistically identical. Interestingly, these results are obtained using data from large-aperture, ground-based telescopes as well as a more modestly sized instrument, and both are in agreement with previous work done using Hubble Space Telescope and Strömgren photometry. Results are derived using the C U,B,I index, shown to be sensitive to compositional differences. We discuss our conclusions that the chemically distinct populations within M13 may be dynamically mixed in the context of published results from simulations.