HST+IGRINS synergy to characterise the newly discovered metal-rich bulge globular cluster Patchick 126
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| Format: | Preprint |
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2026
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| _version_ | 1866917188401627136 |
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| author | Garro, Elisa R. Massari, Davide Fernández-Trincado, José G. Ceccarelli, Edoardo Sneden, Chris Aguado-Agelet, Fernando Afşar, Melike Bellazzini, Michele Guerço, Rafael Minniti, Dante Libralato, Mattia Barbuy, Beatriz Dias, Bruno |
| author_facet | Garro, Elisa R. Massari, Davide Fernández-Trincado, José G. Ceccarelli, Edoardo Sneden, Chris Aguado-Agelet, Fernando Afşar, Melike Bellazzini, Michele Guerço, Rafael Minniti, Dante Libralato, Mattia Barbuy, Beatriz Dias, Bruno |
| contents | We present the first comprehensive spectroscopic and deep photometric study of the globular cluster (GC) candidate Patchick~126. The spectroscopic analysis is based on high-resolution near-infrared data obtained with the IGRINS spectrograph, while the photometric analysis relies on HST observations from the Hubble Missing Globular Cluster Survey (MGCS). We derived abundances for $α$-(O, Mg, Si, Ca, Ti), light-(C, N), odd-Z (Na, Al), iron-peak (Fe, Co, Cr, Ni, Mn, V), and s-process elements (Ce) for four red giant stars observed in the H and K bands. Our results yield a mean metallicity of $\langle\mathrm{[Fe/H]}\rangle = -0.30\pm0.03$, with no evidence of intrinsic variation, and an $α$-enhancement of $\langle\mathrm{[α/Fe]}\rangle =+0.19\pm0.02$, consistent with the trends of metal-rich Galactic GCs. We detect an intrinsic C-N anti-correlation, but no Na-O or Al-Mg anti-correlations, in agreement with expectations for low-mass, metal-rich clusters. From the HST photometry, we constructed deep CMDs extending $\sim 2-3$ magnitudes below the MSTO. This depth allowed us to provide the first robust age estimate for the cluster. Applying the methods developed within the CARMA project, we derive an age of $11.9^{+0.3}_{-0.4}$~Gyr. We obtain a photometric metallicity of [Fe/H]$=-0.28$, in agreement with the spectroscopic results. The colour excess we derived, E(B-V) = 1.08, confirms that Patchick~126 is a heavily reddened cluster, located at a heliocentric distance of 7.8 kpc. From the orbital parameters, including energy, vertical angular momentum, circularity, and maximum vertical height, we find that Patchick~126 closely follows a disc-like orbit. Taken together, these results confirm that Patchick 126 is an in situ, low-mass globular cluster of the Milky Way, exhibiting properties that lie at the boundary between old-OCs and GCs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_03901 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | HST+IGRINS synergy to characterise the newly discovered metal-rich bulge globular cluster Patchick 126 Garro, Elisa R. Massari, Davide Fernández-Trincado, José G. Ceccarelli, Edoardo Sneden, Chris Aguado-Agelet, Fernando Afşar, Melike Bellazzini, Michele Guerço, Rafael Minniti, Dante Libralato, Mattia Barbuy, Beatriz Dias, Bruno Astrophysics of Galaxies We present the first comprehensive spectroscopic and deep photometric study of the globular cluster (GC) candidate Patchick~126. The spectroscopic analysis is based on high-resolution near-infrared data obtained with the IGRINS spectrograph, while the photometric analysis relies on HST observations from the Hubble Missing Globular Cluster Survey (MGCS). We derived abundances for $α$-(O, Mg, Si, Ca, Ti), light-(C, N), odd-Z (Na, Al), iron-peak (Fe, Co, Cr, Ni, Mn, V), and s-process elements (Ce) for four red giant stars observed in the H and K bands. Our results yield a mean metallicity of $\langle\mathrm{[Fe/H]}\rangle = -0.30\pm0.03$, with no evidence of intrinsic variation, and an $α$-enhancement of $\langle\mathrm{[α/Fe]}\rangle =+0.19\pm0.02$, consistent with the trends of metal-rich Galactic GCs. We detect an intrinsic C-N anti-correlation, but no Na-O or Al-Mg anti-correlations, in agreement with expectations for low-mass, metal-rich clusters. From the HST photometry, we constructed deep CMDs extending $\sim 2-3$ magnitudes below the MSTO. This depth allowed us to provide the first robust age estimate for the cluster. Applying the methods developed within the CARMA project, we derive an age of $11.9^{+0.3}_{-0.4}$~Gyr. We obtain a photometric metallicity of [Fe/H]$=-0.28$, in agreement with the spectroscopic results. The colour excess we derived, E(B-V) = 1.08, confirms that Patchick~126 is a heavily reddened cluster, located at a heliocentric distance of 7.8 kpc. From the orbital parameters, including energy, vertical angular momentum, circularity, and maximum vertical height, we find that Patchick~126 closely follows a disc-like orbit. Taken together, these results confirm that Patchick 126 is an in situ, low-mass globular cluster of the Milky Way, exhibiting properties that lie at the boundary between old-OCs and GCs. |
| title | HST+IGRINS synergy to characterise the newly discovered metal-rich bulge globular cluster Patchick 126 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.03901 |