Bayesian ages of nearby stellar associations: The expansion rate method
- Autor(en)
- Javier Olivares, Hervé Bouy, Núria Miret Roig, Phillip A.B. Galli
- Abstrakt
Age is a fundamental parameter for the characterisation of any astrophysical system. In particular, our understanding of the star formation process in the solar vicinity requires accurate and precise age estimates for the nearest star-forming regions, stellar associations, and open clusters. These age estimations can be obtained through diverse dating techniques that have varying applicability domains, accuracies, and precisions. The characterization of these techniques, and their biases, in particular, is thus a fundamental stepping stone.
In this work, we characterize the applicability domain, accuracy, and precision of the expansion rate dating technique, which is a type of dynamical age method that derives ages by inverting the current rate of the system's expansion. We compare the performance of three age estimators (two frequentists and one Bayesian) at recovering the true age value of synthetic stellar associations with varying numbers of members, radial velocity coverages, and observational properties of Gaia DR3 and DR4.
Our results show that, under current observational properties, the expansion rate method is valid for systems younger than 30-35 Myr, and systematic biases are present for the three age estimators, although the Bayesian one shows the best performance and smallest biases. Furthermore, the underestimated uncertainties and large biases of the frequentist estimators produce unreliable ages.
We apply the expansion rate method to the Gaia DR3 data of the closest and youngest stellar associations (i.e., β-Pictoris, TW Hydrae, ɛ-Chamaeleontis, η-Chamaeleontis, 32 Orionis, and 118 Tau) and obtain age estimates that are compatible with the literature values derived from independent age dating techniques, such as isochrone fitting and lithium depletion boundary.
We conclude that literature ages for the closest and youngest stellar associations that are based on the expansion rate method and frequentist estimators tend to be biased and have underestimated uncertainties. On the contrary, the Bayesian age estimator that we present, validate, and make publicly available here, offers better performance than the frequentists ones, in particular, it produces smaller age biases.- Organisation(en)
- Institut für Astrophysik
- Externe Organisation(en)
- Universidad Nacional de Educacion a Distancia (UNED), Laboratoire d'Astrophysique de Bordeaux, Universidade de São Paulo
- Publikationsdatum
- 07-2024
- Peer-reviewed
- Ja
- ÖFOS 2012
- 103003 Astronomie, 103004 Astrophysik
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/879d7ed5-3d33-49fd-b168-86e7b48e2843