Bayesian ages of local young stellar associations

I. Through the expansion rate method

¹ Departamento de Inteligencia Artificial, Universidad Nacional de Educación a Distancia (UNED), c/Juan del Rosal 16, 28040 Madrid, Spain
² Dep. de Física Quàntica i Astrofísica (FQA), Univ. de Barcelona (UB), Martí i Franquès, 1, 08028 Barc., Spain
³ Institut de Ciències del Cosmos (ICCUB), Univ. de Barcelona (UB), Martí i Franquès, 1, 08028 Barcelona, Spain
⁴ Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, Cidade Universitária, 05508-090 São Paulo, SP, Brazil
⁵ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France

^★ Corresponding author: jolivares@dia.uned.es

Received: 25 March 2025
Accepted: 12 May 2025

Abstract

Context. Local young stellar associations (LYSAs <50 Myr and <150 pc) are important laboratories to test predictions from star formation theories. Estimating their ages through various dating techniques with minimal biases is thus of paramount importance.

Aims. We aim to determine the ages of LYSAs with the expansion rate dating technique.

Methods. We estimated the ages of the LYSAs using literature membership lists, publicly available data (astrometry and radial velocities), and a recent open-source Bayesian code that implements the expansion rate method. This code in combination with simple statistical assumptions allowed us to decontaminate, identify possible substructures or populations, and estimate expansion ages.

Results. We derive the largest and most methodological homogeneous set of ages of LYSAs. We rediscover three and discover four associations hidden within the literature membership lists of the classical ones.

Conclusions. The expansion ages we report here are compatible with literature age estimates. Moreover, our analysis shows that previous age tensions can be explained, in most cases, by the presence of unidentified populations or substructures.