The stellar to sub-stellar masses transition in 47 Tuc

TL;DR

This study uses JWST data and stellar evolution models to analyze the stellar to sub-stellar transition in 47 Tuc, revealing the mass at which stars become brown dwarfs and the distribution of different stellar populations.

Contribution

It provides the first detailed interpretation of JWST data for 47 Tuc's low main sequence, distinguishing multiple populations and their mass functions at the stellar to sub-stellar boundary.

Findings

Transition from stellar to sub-stellar occurs at ~0.07-0.074 solar masses.

First generation constitutes 45% of the cluster, second generation 55%.

Mass functions follow a Kroupa-like profile down to 0.22 solar masses.

Abstract

Context: The study of the Globular Cluster 47 Tuc offers the opportunity to shed new light on the debated issue on the presence of multiple populations in Globular Clusters, as recent results from HST photometry and high-resolution spectroscopy outlined star-to-star differences in the surface chemical composition. Aims: The goal of the present investigation is the interpretation of recent JWST data of the low main sequence of 47 Tuc, in order to explore the stellar to sub-stellar transition, to derive the mass distribution of the individual sources and to disentangle stars from different populations. Methods: Stellar evolution modelling of low-mass stars of metallicity [Fe/H]=-0.78 and oxygen content [O/Fe]=+0.4 and [O/Fe]=0 is used to simulate the evolution of the first and the second generation of the cluster. The comparison between the calculated sequences with the data points is used to characterize the individual objects, to split the different stellar components and to infer the current mass function of the cluster. Results: The first generation of 47 Tuc harbours 45 % of the overall population of the cluster, the remaining 55 % making up the second generation. The transition from the stellar to the sub-stellar domain is found at $0.074 M_{\odot}$ and $0.07 M_{\odot}$ for the first and second generations, respectively. The mass function of both the stellar generations are consistent with a Kroupa-like profile down to $0.22 M_\odot$.