Astronomy & Telescopes

A JWST Project On 47 Tucanae. Overview, Photometry And Early Spectroscopic Results Of M dwarfs And Observation Of Brown Dwarfs

By Keith Cowing
Status Report
January 16, 2024
Filed under , , , , , , ,
A JWST Project On 47 Tucanae. Overview, Photometry And Early Spectroscopic Results Of M dwarfs And Observation Of Brown Dwarfs
Footprints of the images used in our work on 47 Tucanae. Red and orange colors represent the JWST and HST images, respectively, of field A, whereas the JWST and HST footprints of field B are colored blue and azure, respectively. Magenta and pink colors indicate JWST and HST images of field C. — astro-ph.SR

The James Webb Space Telescope (JWST) observations have been demonstrated to be efficient in detecting globular clusters’ (GCs) multiple stellar populations in the low-mass regime of M dwarfs.

We present an overview, and first results, of different projects that can be explored by using the JWST observations gathered under the GO2560 for 47 Tucanae, a first program entirely devoted to the investigation of multiple populations in very low mass stars, which includes spectroscopic data for the faintest GC stars for which spectra are available.

Our color-magnitude diagram (CMD) shows some substructures for ultracool stars, including gaps. In particular, we observe a minimum in the F322W2 luminosity function, that we tentatively associate with the H-burning limit.

We detect stars fainter than this minimum, very likely the brown dwarfs. We corroborate the ubiquity of the multiple populations across different masses, from ~0.1 solar masses up to red giants (~0.8 solar masses). The oxygen range inferred from the M dwarfs, both from the CMD and from the NIRSpec spectra of two M dwarfs associated with different populations, is similar to that observed in giants from high-resolution spectra.

We have not detected any change between the fractions of stars in different populations across stellar masses >~0.1 solar masses. This work demonstrates the JWST’s capability in uncovering multiple populations within M dwarfs and illustrates the possibility to analyse very low-mass stars in GCs approaching the H-burning limit and the brown-dwarf sequence.

The JWST data will mark a pivotal advancement in our understanding of these poorly-explored issues.

Top. Three-color (RGB) image of a portion of the studied field of view (field C). We used the stacked F115W and F322W2 images for the B and R channels, respectively, whereas the G channel is obtained by averaging the F115W and F322W2 stacked images (left). The right panels show the F322W2 (top) and F115W (bottom) stacked images for the region within the yellow box highlighted in the field of view on the left panel. Bottom. mF322W2 vs. mF115W − mF322W2 CMD of stars in field C (left). The arrows indicate the location of the possible gaps or discontinuities along the sequence of ultra-cold 47 Tucanae stars. Stars fainter than mF322W2 ∼ 25.3 mag and with colors redder than mF115W − mF322W2 ∼ 1.5 mag are probable brown dwarfs. The blue and red circles in the CMD highlight two of them, which are also marked in the top-right panel. We choose these two stars, among the brown dwarf sample, for illustrative purposes, as they are located in a relatively small region of the field of view. A zoom around the MS region of 47 Tucanae populated by M-dwarfs is shown in the right panel. — astro-ph.SR

A. F. Marino, A. P. Milone, M. V. Legnardi, A. Renzini, E. Dondoglio, Y. Cavecchi, G. Cordoni, A. Dotter, E.P. Lagioia, T. Ziliotto, M. Bernizzoni, E. Bortolan, M. G. Carlos, S. Jang, A. Mohandasan, F. Muratore, M. Tailo

Comments: 18 pages, 10 figures, 2 tables, submitted
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2401.06681 [astro-ph.SR] (or arXiv:2401.06681v1 [astro-ph.SR] for this version)
Submission history
From: Anna Fabiola Marino
[v1] Fri, 12 Jan 2024 16:40:55 UTC (4,606 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻