The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters

XXII. Relative ages of multiple populations in five globular clusters

¹ Departamento de Física, Faculdad de Ciencia Exactas, Universidad Andrés Bello, Fernández Concha 700, Santiago, Chile
e-mail: lucertini.fra@gmail.com
² Aix Marseille Univ., CNRS, CNES, LAM, Marseille, France
³ Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova, IT 35122, Italy
⁴ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Universitá di Padova, Vicolo dell’Osservatorio 3, Padova, IT 35122, Italy

Received: 15 September 2020
Accepted: 9 December 2020

Abstract

Aims. We present a new technique to estimate the relative ages of multiple stellar populations hosted by the following five globular clusters: NGC 104 (47 Tuc), NGC 6121 (M 4), NGC 6352, NGC 6362, and NGC 6723.

Methods. We used the catalogs of the database HST UV Globular Cluster Survey to create color-magnitude and two-color diagrams of the globular clusters. We identified the multiple populations within each globular cluster, and we divided these into two main stellar populations: POPa, or first generation; and POPb, which is composed of all the successive generations of stars. This new technique allows us to obtain an accurate estimate of the relative ages between POPa and POPb.

Results. The multiple populations of NGC 104 and NGC 6121 are coeval within 220 Myr and 214 Myr, while those of NGC 6352, NGC 6362, and NGC 6723 are coeval within 336 Myr, 474 Myr, and 634 Myr, respectively. These results were obtained combining all the sources of uncertainties.