JWST Imaging of the Closest Globular Clusters -- VI. The Lowest-Mass Objects in M 4 and the Galactic Bulge
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866913948513599488 |
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| author | Bedin, L. R. Gerasimov, R. Calamida, A. Libralato, M. Scalco, M. Nardiello, D. Griggio, M. Apai, D. Anderson, J. Bellini, A. Burgasser, A. J. |
| author_facet | Bedin, L. R. Gerasimov, R. Calamida, A. Libralato, M. Scalco, M. Nardiello, D. Griggio, M. Apai, D. Anderson, J. Bellini, A. Burgasser, A. J. |
| contents | We present `James Webb Space Telescope' observations of M4 -- the closest globular cluster -- that probe the lower Main Sequence down to the hydrogen-burning limit. The unveiled stellar sequence reaches much fainter luminosities than previously possible, revealing a few extremely red objects that are consistent with brown dwarfs as cool as T_eff~1000K. However, the lack of a second JWST epoch presently prevents us from verifying the cluster membership of these objects. By cross-matching our data with archival `Hubble Space Telescope' images, we are able to verify cluster membership for a subset of objects down to T_eff~3000K. The observed color distribution indicate that the lower Main Sequence of M4 is likely deficient in oxygen compared to its higher-mass post-Main Sequence members by ~0.5dex. This feature has now been observed in three different globular clusters (M4, NGC6397 and 47Tuc), suggesting a general trend. Finally, we derive the mass function of the Galactic bulge in the background of M4. The mass function was found to have the bottom-heavy slope of alpha=0.88+/-0.36 and appears to terminate at ~0.15 M_Sun, although the latter value may be overestimated due to the limited sample size. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_13564 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | JWST Imaging of the Closest Globular Clusters -- VI. The Lowest-Mass Objects in M 4 and the Galactic Bulge Bedin, L. R. Gerasimov, R. Calamida, A. Libralato, M. Scalco, M. Nardiello, D. Griggio, M. Apai, D. Anderson, J. Bellini, A. Burgasser, A. J. Solar and Stellar Astrophysics Astrophysics of Galaxies We present `James Webb Space Telescope' observations of M4 -- the closest globular cluster -- that probe the lower Main Sequence down to the hydrogen-burning limit. The unveiled stellar sequence reaches much fainter luminosities than previously possible, revealing a few extremely red objects that are consistent with brown dwarfs as cool as T_eff~1000K. However, the lack of a second JWST epoch presently prevents us from verifying the cluster membership of these objects. By cross-matching our data with archival `Hubble Space Telescope' images, we are able to verify cluster membership for a subset of objects down to T_eff~3000K. The observed color distribution indicate that the lower Main Sequence of M4 is likely deficient in oxygen compared to its higher-mass post-Main Sequence members by ~0.5dex. This feature has now been observed in three different globular clusters (M4, NGC6397 and 47Tuc), suggesting a general trend. Finally, we derive the mass function of the Galactic bulge in the background of M4. The mass function was found to have the bottom-heavy slope of alpha=0.88+/-0.36 and appears to terminate at ~0.15 M_Sun, although the latter value may be overestimated due to the limited sample size. |
| title | JWST Imaging of the Closest Globular Clusters -- VI. The Lowest-Mass Objects in M 4 and the Galactic Bulge |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.13564 |