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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2511.13161 |
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| _version_ | 1866917264556556288 |
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| author | Moya, W. Haro Bidin, C. Moni Parisi, M. C. Geisler, D. Blaña, M. Villanova, S. Mauro, F. Chené, A. -N. Cohen, R. E. Alegría, S. Ramírez Ramos, R. Contreras Zoccali, M. Muñoz, C. Dias, B. |
| author_facet | Moya, W. Haro Bidin, C. Moni Parisi, M. C. Geisler, D. Blaña, M. Villanova, S. Mauro, F. Chené, A. -N. Cohen, R. E. Alegría, S. Ramírez Ramos, R. Contreras Zoccali, M. Muñoz, C. Dias, B. |
| contents | Globular clusters in the Galactic bulge are difficult to study due to high extinction and severe crowding. VVV-CL001 is an old, metal-poor, and fast cluster in the inner bulge, whose extreme properties make it a key probe of the early chemical and dynamical evolution of the Milky Way. We derive its fundamental parameters by combining spectroscopy, astrometry, and near-infrared photometry. Metallicity and radial velocity were measured from medium-resolution FORS2/VLT spectra; proper motions from Gaia DR3; and FourStar/Magellan photometry was used to refine the cluster centre, derive its structure, and estimate age, distance, and reddening. VVV-CL001 is confirmed to be an old ($12.1^{+1.0}_{-1.2}$ Gyr), metal-poor ($[\text{Fe}/\text{H}] = -2.25 \pm 0.05$) cluster at a heliocentric distance of $7.1^{+1.3}_{-1.1}$ kpc, with reddening $E(J-K_s) = 1.40^{+0.01}_{-0.02}$. Its mean proper motions are $μ_α^* = -3.68 \pm 0.09$ and $μ_δ= -1.76 \pm 0.10$ mas yr$^{-1}$, and its radial velocity is $-334 \pm 4$ km s$^{-1}$. The orbit is eccentric ($e = 0.76^{+0.10}_{-0.14}$), confined to the inner Galaxy ($|Z|_{\max} \approx 1$ kpc) and within the bar's influence ($R < 5$ kpc), with pericentre $0.6^{+0.3}_{-0.2}$ kpc and apocentre $4.5^{+2.5}_{-1.2}$ kpc. Its old age, low metallicity, and orbital properties support an in-situ origin, identifying VVV-CL001 as one of the most metal-poor inner-Galaxy clusters formed in the early Milky Way. It likely belongs to the primordial disk cluster population later trapped by the bar, making it a fossil remnant of the earliest phases of Galactic assembly. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_13161 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Infrared photometry and CaT spectroscopy of the most metal-poor in-situ globular cluster VVV-CL001 Moya, W. Haro Bidin, C. Moni Parisi, M. C. Geisler, D. Blaña, M. Villanova, S. Mauro, F. Chené, A. -N. Cohen, R. E. Alegría, S. Ramírez Ramos, R. Contreras Zoccali, M. Muñoz, C. Dias, B. Astrophysics of Galaxies Globular clusters in the Galactic bulge are difficult to study due to high extinction and severe crowding. VVV-CL001 is an old, metal-poor, and fast cluster in the inner bulge, whose extreme properties make it a key probe of the early chemical and dynamical evolution of the Milky Way. We derive its fundamental parameters by combining spectroscopy, astrometry, and near-infrared photometry. Metallicity and radial velocity were measured from medium-resolution FORS2/VLT spectra; proper motions from Gaia DR3; and FourStar/Magellan photometry was used to refine the cluster centre, derive its structure, and estimate age, distance, and reddening. VVV-CL001 is confirmed to be an old ($12.1^{+1.0}_{-1.2}$ Gyr), metal-poor ($[\text{Fe}/\text{H}] = -2.25 \pm 0.05$) cluster at a heliocentric distance of $7.1^{+1.3}_{-1.1}$ kpc, with reddening $E(J-K_s) = 1.40^{+0.01}_{-0.02}$. Its mean proper motions are $μ_α^* = -3.68 \pm 0.09$ and $μ_δ= -1.76 \pm 0.10$ mas yr$^{-1}$, and its radial velocity is $-334 \pm 4$ km s$^{-1}$. The orbit is eccentric ($e = 0.76^{+0.10}_{-0.14}$), confined to the inner Galaxy ($|Z|_{\max} \approx 1$ kpc) and within the bar's influence ($R < 5$ kpc), with pericentre $0.6^{+0.3}_{-0.2}$ kpc and apocentre $4.5^{+2.5}_{-1.2}$ kpc. Its old age, low metallicity, and orbital properties support an in-situ origin, identifying VVV-CL001 as one of the most metal-poor inner-Galaxy clusters formed in the early Milky Way. It likely belongs to the primordial disk cluster population later trapped by the bar, making it a fossil remnant of the earliest phases of Galactic assembly. |
| title | Infrared photometry and CaT spectroscopy of the most metal-poor in-situ globular cluster VVV-CL001 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2511.13161 |