The Absolute Age of Milky Way Globular Clusters
Globular clusters (GCs) provide statistically significant coeval populations of stars spanning various evolutionary stages, allowing robust constraints on stellar evolution model parameters and ages. We analyze eight old Milky Way GCs with metallicities between [Fe/H] = −2.31 and −0.77 by comparing...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/add471 |
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| author | Jiaqi (Martin) Ying Brian Chaboyer Michael Boylan-Kolchin Daniel R. Weisz Rowan Goebel-Bain |
| author_facet | Jiaqi (Martin) Ying Brian Chaboyer Michael Boylan-Kolchin Daniel R. Weisz Rowan Goebel-Bain |
| author_sort | Jiaqi (Martin) Ying |
| collection | DOAJ |
| description | Globular clusters (GCs) provide statistically significant coeval populations of stars spanning various evolutionary stages, allowing robust constraints on stellar evolution model parameters and ages. We analyze eight old Milky Way GCs with metallicities between [Fe/H] = −2.31 and −0.77 by comparing theoretical isochrone sets from the Dartmouth Stellar Evolution Program to Hubble Space Telescope (HST) observations. The theoretical isochrones include uncertainties introduced by 21 stellar evolution parameters such as convective mixing, opacity, diffusion, and nuclear reactions, capturing much of the quantifiable physics used in our code. For each isochrone, we construct simulated color–magnitude diagrams (CMDs) near the main-sequence turnoff region and apply two full-CMD-fitting methods to fit HST Advanced Camera for Surveys data across a range of distances and reddening and measure the absolute age of each GC from the resulting posterior distribution, which accounts for uncertainties in the stellar models, observations, and fitting method. The resulting best-fitting absolute ages range from ≈11.5 to 13.5 Gyr, with a typical error of 0.5–0.75 Gyr; the data show a clear trend toward older ages at lower metallicities. Notably, distance and reddening account for over 50% of the uncertainty in age determination in each case, with metallicity, α abundance, mixing length, and helium diffusion being the most important stellar physics parameters for the error budget. We also provide an absolute age–metallicity relation for Milky Way GCs. |
| format | Article |
| id | doaj-art-ec6570ad6d3f43e29549ff1217b71e9a |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-ec6570ad6d3f43e29549ff1217b71e9a2025-08-20T02:22:06ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198715210.3847/1538-4357/add471The Absolute Age of Milky Way Globular ClustersJiaqi (Martin) Ying0https://orcid.org/0009-0006-5300-2976Brian Chaboyer1https://orcid.org/0000-0003-3096-4161Michael Boylan-Kolchin2https://orcid.org/0000-0002-9604-343XDaniel R. Weisz3https://orcid.org/0000-0002-6442-6030Rowan Goebel-Bain4Department of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USADepartment of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USADepartment of Astronomy, The University of Texas at Austin , TX 78712, USADepartment of Astronomy, University of California Berkeley , CA 94720, USADepartment of Physics and Astronomy, Dartmouth College , 6127 Wilder Laboratory, Hanover, NH 03755, USAGlobular clusters (GCs) provide statistically significant coeval populations of stars spanning various evolutionary stages, allowing robust constraints on stellar evolution model parameters and ages. We analyze eight old Milky Way GCs with metallicities between [Fe/H] = −2.31 and −0.77 by comparing theoretical isochrone sets from the Dartmouth Stellar Evolution Program to Hubble Space Telescope (HST) observations. The theoretical isochrones include uncertainties introduced by 21 stellar evolution parameters such as convective mixing, opacity, diffusion, and nuclear reactions, capturing much of the quantifiable physics used in our code. For each isochrone, we construct simulated color–magnitude diagrams (CMDs) near the main-sequence turnoff region and apply two full-CMD-fitting methods to fit HST Advanced Camera for Surveys data across a range of distances and reddening and measure the absolute age of each GC from the resulting posterior distribution, which accounts for uncertainties in the stellar models, observations, and fitting method. The resulting best-fitting absolute ages range from ≈11.5 to 13.5 Gyr, with a typical error of 0.5–0.75 Gyr; the data show a clear trend toward older ages at lower metallicities. Notably, distance and reddening account for over 50% of the uncertainty in age determination in each case, with metallicity, α abundance, mixing length, and helium diffusion being the most important stellar physics parameters for the error budget. We also provide an absolute age–metallicity relation for Milky Way GCs.https://doi.org/10.3847/1538-4357/add471Stellar physicsCosmologyGlobular star clustersComputational astronomyStellar evolutionary models |
| spellingShingle | Jiaqi (Martin) Ying Brian Chaboyer Michael Boylan-Kolchin Daniel R. Weisz Rowan Goebel-Bain The Absolute Age of Milky Way Globular Clusters The Astrophysical Journal Stellar physics Cosmology Globular star clusters Computational astronomy Stellar evolutionary models |
| title | The Absolute Age of Milky Way Globular Clusters |
| title_full | The Absolute Age of Milky Way Globular Clusters |
| title_fullStr | The Absolute Age of Milky Way Globular Clusters |
| title_full_unstemmed | The Absolute Age of Milky Way Globular Clusters |
| title_short | The Absolute Age of Milky Way Globular Clusters |
| title_sort | absolute age of milky way globular clusters |
| topic | Stellar physics Cosmology Globular star clusters Computational astronomy Stellar evolutionary models |
| url | https://doi.org/10.3847/1538-4357/add471 |
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