No evidence of mass segregation in the low mass Galactic globular cluster NGC 6101

TL;DR

This study finds no evidence of mass segregation in the low-mass globular cluster NGC 6101, challenging expectations of dynamical evolution in such systems and supporting the use of Blue Straggler distribution as a dynamical age indicator.

Contribution

The paper provides the first comprehensive analysis showing the absence of mass segregation in NGC 6101 using multiple indicators, highlighting its dynamical youth.

Findings

NGC 6101 is more extended than previously thought.

No evidence of mass segregation in BSS, binaries, or luminosity functions.

Supports the 'dynamical clock' concept for cluster age assessment.

Abstract

We used a combination of Hubble Space Telescope and ground based data to probe the dynamical state of the low mass Galactic globular cluster NGC 6101. We have re-derived the structural parameters of the cluster by using star counts and we find that it is about three times more extended than thought before. By using three different indicators, namely the radial distribution of Blue Straggler Stars, that of Main Sequence binaries and the luminosity (mass) function, we demonstrated that NGC 6101 shows no evidence of mass segregation, even in the innermost regions. Indeed, both the BSS and the binary radial distributions fully resemble that of any other cluster population. In addition the slope of the luminosity (mass) functions does not change with the distance, as expected for non relaxed stellar systems. NGC 6101 is one of the few globulars where the absence of mass segregation has been observed so far. This result provides additional support to the use of the "dynamical clock" calibrated on the radial distribution of the Blue Stragglers as a powerful indicator of the cluster dynamical age.