Re-examining the Radial Distributions of M13 Multiple Populations

TL;DR

This study investigates the radial distribution of multiple stellar populations in globular cluster M13, finding no significant segregation and suggesting these populations are dynamically mixed, consistent across various observational methods.

Contribution

It provides a comprehensive analysis using multiple photometric datasets, demonstrating that M13's populations are radially mixed, resolving previous conflicting reports.

Findings

Radial distributions of populations are statistically identical

Results are consistent across different telescopes and photometric methods

Supports the idea of dynamical mixing of populations in M13

Abstract

We seek to resolve the tension in the literature regarding the presence of radially segregated multiple populations in 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 HST and Stromgren 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.