JWST uncovers helium and water abundance variations in the bulge globular cluster NGC 6440

Cadelano, Mario; Pallanca, Cristina; Dalessandro, Emanuele; Salaris, Maurizio; Mucciarelli, Alessio; Leanza, Silvia; Ferraro, Francesco R.; Lanzoni, Barbara; Rosie Chen, C.-H.; Freire, Paulo C. C.; Heinke, Craig; Ransom, Scott M.

doi:10.1051/0004-6361/202347961

Cited by 9 publications

(2 citation statements)

References 47 publications

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“…Dondoglio et al (2022) present an analysis of a sample of GCs below the MS knee, and provided for the first time, the MFs of MPs in NGC 2808 and M4 along a wide range of stellar masses, from ∼0.2 to ∼0.8 M e , finding that the fraction of MPs does not depend on stellar mass, thus further challenging the accretion scenario. First evidence of multiple stellar populations in verylow-mass stars from JWST data has been reported for 47 Tucanae (Milone et al 2023a), M92 (Ziliotto et al 2023), and NGC 6440 (Cadelano et al 2023). In this paper we exploit deep JWST data to reach well below the hydrogen-burning limit in 47 Tucanae, and into the brown-dwarf regime.…”

Section: Introductionmentioning

confidence: 98%

A JWST Project on 47 Tucanae. Overview, Photometry, and Early Spectroscopic Results of M Dwarfs and Observations of Brown Dwarfs*

Marino,

Milone,

Legnardi

et al. 2024

ApJ

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James Webb Space Telescope (JWST) observations have been demonstrated to be efficient in detecting multiple stellar populations in globular clusters (GCs) 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 program GO2560 for 47 Tucanae, the 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 and breaks in slope. In particular, we observe both a gap and a minimum in the F322W2 luminosity function less than 1 mag apart, and discuss which it could be associated with the H-burning limit. We detect stars fainter than this minimum, very likely brown dwarfs. We corroborate the ubiquity of the multiple populations across different masses, from ∼0.1 M ⊙ up to red giants (∼0.8 M ⊙). The oxygen range inferred for the M dwarfs, both from the CMD and from the spectra of two M dwarfs associated with different populations, is similar to that observed for giants. We have not detected any difference between the fractions of stars in distinct populations across stellar masses ≳ 0.1 M ⊙. This work demonstrates the JWST's capability in uncovering multiple populations within M dwarfs and illustrates the possibility to analyze very-low-mass stars in GCs approaching the H-burning limit and the brown-dwarf sequence.

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Section: Introductionmentioning

confidence: 98%

A JWST Project on 47 Tucanae. Overview, Photometry, and Early Spectroscopic Results of M Dwarfs and Observations of Brown Dwarfs*

Marino,

Milone,

Legnardi

et al. 2024

ApJ

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“…Now, thanks to the new facilities on board the James Webb Space Telescope (JWST), the observation of GC stars down to very faint magnitudes has become considerably more efficient than with previous telescopes. The first evidence of multiple stellar populations in very low-mass stars below the mainsequence knee has been reported for NGC 104 (47 Tucanae; Milone et al 2023), M 92 (Ziliotto et al 2023), and NGC 6440 (Cadelano et al 2023), using H 2 O blanketing (e.g., in the F150W, F200W, or F322W2 bands). Most recently, the CMD of 47 Tucanae from very deep JWST/NIRCam data has reached, for the first time, the H-burning limit and the more luminous brown dwarfs (Marino et al 2024).…”

Section: Introductionmentioning

confidence: 99%

A JWST Project on 47 Tucanae: NIRSpec Spectroscopy of Multiple Populations among M Dwarfs*

Marino,

Milone,

Renzini

et al. 2024

ApJL

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We present the first spectroscopic estimates of the chemical abundance of M dwarf stars in a globular cluster (GC), namely 47 Tucanae. By exploiting NIRSpec on board the James Webb Space Telescope, we gathered low-resolution spectra for 28 stars with masses in the range ∼0.4–0.5 M ⊙. The spectra are strongly affected by the H2O water vapor bands, which can be used as indicators of oxygen abundance. The spectral analysis reveals that the target stars feature a different O abundance, with a difference of ∼0.40 dex between the first and the most polluted second population. The observed range is similar to that observed among red giant stars. This result reinforces previous findings based on the analysis of photometric diagrams, including the “chromosome maps,” providing a first, and more direct, evidence of light element variations in the M dwarfs’ mass regime. The observation that the multiple populations, with their variations in light elements, exhibit the same patterns from the lower main sequence all the way to the red giant branch further strengthens the notion that multiple stellar populations in GCs formed in a series of bursts of star formation.

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The structural properties of multiple populations in globular clusters: The instructive case of NGC 3201

Cadelano,

Dalessandro,

Vesperini

2024

A&A

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All multiple population (MP) formation models in globular clusters (GCs) predict that second population (SP) stars form more centrally concentrated than the first population (FP). As dynamical evolution proceeds, spatial differences are progressively erased and only dynamically young clusters are expected to retain a partial memory of the initial structural differences. In recent years, this picture has been supported by observations of the MP radial distributions of both Galactic and extragalactic GCs. However, more recent observations have suggested that in some systems, FPs might actually form more centrally segregated, with NGC 3201 being one significant example of such a possibility. Here, we present a detailed morphological and kinematic characterization of the MPs in NGC 3201, based on a combination of photometric and astrometric data. We show that the distribution of the SP is clearly bimodal. Specifically, the SP is significantly more centrally concentrated than the FP within $ cluster’s half-mass radius. Beyond this point, the SP fraction increases again, likely due to asymmetries in the spatial distributions of the two populations. The central concentration of the SP observed in the central regions implies that it formed more centrally concentrated than the FP, even more so than what is observed in the present-day. This interpretation is supported by the key information provided by the MP kinematic properties. Indeed, we find that the FP is isotropic across all the sampled cluster extension, while the velocity distribution of the SP becomes radially anisotropic in the cluster’s outer regions, as expected for the dynamical evolution of SP stars formed more centrally concentrated than the FP. The combination of spatial and kinematic observations provide key insights into the dynamical properties of this cluster and lend further support to scenarios in which the SP forms more centrally concentrated than the FP.

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JWST uncovers helium and water abundance variations in the bulge globular cluster NGC 6440

Cited by 9 publications

References 47 publications

A JWST Project on 47 Tucanae. Overview, Photometry, and Early Spectroscopic Results of M Dwarfs and Observations of Brown Dwarfs*

A JWST Project on 47 Tucanae. Overview, Photometry, and Early Spectroscopic Results of M Dwarfs and Observations of Brown Dwarfs*

A JWST Project on 47 Tucanae: NIRSpec Spectroscopy of Multiple Populations among M Dwarfs*

The structural properties of multiple populations in globular clusters: The instructive case of NGC 3201

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