A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood

2015/08/24 by Cameron P. M. Bell, Eric E. Mamajek, T. Naylor +1 · 1 citation
Chemistry · Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Chemistry #Demography #Open cluster #Physics #Population #Stars #Stellar, planetary, and galactic studies #astro-ph.GA #astro-ph.SR #myr

paper · pdf · doi:10.1093/mnras/stv1981

Accepted for publication in MNRAS, 24 pages, 12 figures and 2 tables

arxiv created 2015/08/24 · openalex publication_date 2015/09/24 · arxiv updated 2015/09/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We present a self-consistent, absolute isochronal age scale for young ( ≲ 200 Myr), nearby ( ≲ 100 pc) moving groups in the solar neighbourhood based on homogeneous fitting of semi-empirical pre-main-sequence model isochrones using the τ2 maximum-likelihood fitting statistic of Naylor & Jeffries in the MV, V − J colour–magnitude diagram. The final adopted ages for the groups are as follows: |149⁺⁵¹_-19 \rm Myr| for the AB Dor moving group, 24 ± 3 Myr for the β Pic moving group (BPMG), |45⁺¹¹_-7 \rm Myr| for the Carina association, |42⁺⁶_-4 \rm Myr| for the Columba association, 11 ± 3 Myr for the η Cha cluster, 45 ± 4 Myr for the Tucana–Horologium moving group (Tuc–Hor), 10 ± 3 Myr for the TW Hya association and |22⁺⁴_-3 \rm Myr| for the 32 Ori group. At this stage we are uncomfortable assigning a final, unambiguous age to the Argus association as our membership list for the association appears to suffer from a high level of contamination, and therefore it remains unclear whether these stars represent a single population of coeval stars. Our isochronal ages for both the BPMG and Tuc–Hor are consistent with recent lithium depletion boundary (LDB) ages, which unlike isochronal ages, are relatively insensitive to the choice of low-mass evolutionary models. This consistency between the isochronal and LDB ages instils confidence that our self-consistent, absolute age scale for young, nearby moving groups is robust, and hence we suggest that these ages be adopted for future studies of these groups. Software implementing the methods described in this study is available from http://www.astro.ex.ac.uk/people/timn/tau-squared/.

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