JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit

@misc{scalco2026jwst,
  title = {{JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit}},
  author = {M. Scalco and R. Gerasimov and L. R. Bedin and E. Vesperini and M. Griggio and D. Nardiello and J. Anderson},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.18995},
  eprint = {2610.18995},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.18995},
}

TY  - UNPB
TI  - JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit
AU  - M. Scalco
AU  - R. Gerasimov
AU  - L. R. Bedin
AU  - E. Vesperini
AU  - M. Griggio
AU  - D. Nardiello
AU  - J. Anderson
PY  - 2026
DA  - 2026/10/13
PB  - arXiv
DO  - 10.48550/arxiv.2610.18995
UR  - https://arxiv.org/abs/2610.18995
AB  - We present the first results of a series of studies based on JWST observations of the globular cluster 47 Tucanae (47 Tuc, or NGC 104) obtained with NIRCam. By combining new data with earlier JWST observations, we derive high-precision proper motions (PMs) over a multi-year baseline (of ~3 years) and construct a clean sample of cluster members extending to very faint magnitudes (F444W~24.25 mag, corresponding to ~0.077 solar masses, slightly above the estimated hydrogen-burning limit of 47 Tuc, ~0.074 solar masses) along the main sequence (MS). We investigated the presence of the low-mass MS kink previously identified in 47 Tuc using the new F090W and F444W photometry. No significant signature of the feature is found using these filters, consistent with its proposed physical interpretation as a consequence of the transition in carbon chemistry toward a methane-dominated equilibrium in very low-mass stars. A comparison with theoretical isochrones indicates that the stellar population near the bottom of the MS is likely dominated by oxygen-poor stars, in agreement with previous findings. Using artificial-star tests, we quantify the completeness of our sample and show that the requirement of PM-based membership significantly limits the detection of the faintest objects, indicating that current JWST observations of 47 Tuc are not sufficiently deep to reliably trace the cluster's brown dwarf cooling sequence. The mass function (MF) of 47 Tuc shows a structured behaviour, with a break at ~0.15 solar masses not associated with the onset of convection, and a mild but systematic radial variation consistent with mass segregation. Our analysis indicates that the MF shape in this mass regime is more complex than a simple power-law description. This feature in the MF may point to a presently unrecognised mechanism affecting the formation or dynamical evolution of low-mass stars in globular clusters.
ER  -