The stellar to sub-stellar masses transition in 47 Tuc

¹ INAF, Observatory of Rome, Via Frascati 33, 00077 Monte Porzio Catone (RM), Italy
² Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ Dipartimento di Fisica e Astronomia Augusto Righi, Università degli Studi di Bologna, Bologna, Italy
⁴ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Univ. di Padova, Padova, Italy
⁵ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00100 Roma, Italy

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 4 November 2025
Accepted: 14 December 2025

Abstract

Context. The study of the globular cluster 47 Tuc offers an opportunity to shed new light on the debated issue of 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, derive the mass distribution of the individual sources, and 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 was 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 was used to characterise the individual objects, split the different stellar components, and 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 _⊙ and 0.07 M_⊙ for the first and second generations, respectively. The mass function of both stellar generations is consistent with a Kroupa-like profile down to ~0.22 M_⊙.