Brown dwarfs or white dwarfs with debris disks? Exploring the faintest stars of 47 Tucanae with HST and JWST

0 Assigned ID: 6211 ----- Attempting Submission 1 (Wed Apr 09 08:46:38 GMT 2025) ----- 0 ----- Attempting Submission 1 (Wed Jul 23 15:46:17 GMT 2025) ----- ----- Attempting Submission 2 (Mon Dec 01 23:17:46 GMT 2025) ----- Brown dwarfs or white dwarfs with debris disks? Exploring the faintest stars of 47 Tucanae with HST and JWST Recent JWST photometry has identified a sequence of ultracool stars in 47 Tucanae, potentially representing a population of brown dwarfs. If this hypothesis holds, the abundance of brown dwarfs would significantly exceed predictions based on a standard mass function. However, JWST's infrared capability alone is insufficient to distinguish between brown dwarfs and potential white dwarfs with debris disks. To investigate this faint stellar population further, we propose deep UVIS/WFC3 observations in the F606W filter, which is the only dataset that, combined with archival NIRCam data, allows us to examine whether stars in this color-magnitude diagram (CMD) region, traditionally linked to brown dwarfs, may also include white dwarfs with debris disks. By analyzing the distribution of stars in CMDs generated with the new F606W observations alongside archival JWST data in the F115W and F322W2 bands, we aim to test two scenarios: (1) if these stars are exclusively brown dwarfs, they will remain undetected in F606W due to their low luminosity in this band; (2) if a subset comprises white dwarfs with debris disks, these stars will follow the white dwarf cooling sequence, as debris disk flux primarily enhances F322W2 but has minimal impact on F606W and F115W. This study seeks to refine our understanding of low-mass object distributions in globular clusters and may provide new insights into planetary system remnants around white dwarfs. We propose deep HST/UVIS observations in the F606W filter to study faint stellar populations specifically white dwarfs and M-dwarfs, in the Galactic globular cluster 47 Tucanae (NGC 104). The observations are dithered and distributed across 13 single-orbit visits to maximize scheduling flexibility within HST's constraints. The field is centered at RA = 00h 20m 58.8s, Dec = -72 -06 -30.6, in the outer regions of 47 Tucanae, and overlaps with JWST/NIRCam data collected as part of Program 2560. Our team consists of specialists in data analysis and reduction of HST and JWST images, including G. Cordoni, E. Dondoglio, E. Lagioia, M. V. Legnardi, and A. P. Milone. We have extensively applied the methods and tools discussed in this proposal to derive high-precision photometry, astrometry, and proper motions for stars in hundreds of star clusters using HST data (e.g., Milone et al., 2023, A&A 672, 161). Our team also includes experts in spectroscopy and the analysis of M- and brown dwarfs using NIRCam and NIRSpec data (Marino et al., 2024) as well as specialists in stellar modeling (M. Tailo). Additionally, our team includes PhD students who will benefit from the proposed dataset to support their thesis research. In summary, we are fully prepared and equipped to carry out the proposed research. Stellar Physics and Stellar Types Stellar Populations and the Interstellar Medium 6 false false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER J2000 J2000 WFC3/UVIS Imaging No No F606W POS-TARG DITHER 6 LINE false false 2 100 LINE 1

false

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