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Arxiv: JWST photometry and astrometry of 47 Tucanae. Discontinuity in the stellar sequence at the star/brown dwarf transition Published: 1/8/2025 1:53:55 PM Updated: 1/8/2025 1:53:55 PM

Paper abstract: Using JWST Near Infrared Camera (NIRCam) images of the globular cluster 47Tucanae (or NGC 104), taken at two epochs just 7 months apart, we derivedproper-motion membership down to m_{\rm F322W2} ~ 27. We identified anintriguing feature at the very low-mass end of the main sequence, around ~0.08 solar masses, at magnitudes m_{\rm F322W2} ~ 24 and m_{\rm F150W2}~ 25. This feature, dubbed "kink", is characterized by a prominentdiscontinuity in the slope of the main sequence. A similar discontinuity isseen in theoretical isochrones with oxygen-poor chemistries, related to therapid onset of CH_4 absorption. We therefore hypothesize that the clusterhosts disproportionately more oxygen-poor stars near the bottom of the mainsequence compared to the upper main sequence and the red giant branch. Ourresults show no strong or conclusive evidence of a rise in the brown dwarfluminosity function at faint magnitudes, in contrast to previous findingslikely affected by faint red background galaxies. In our analysis, we accountedfor this contamination by using proper motion membership.