Pre-main-sequence isochrones – II. Revising star and planet formation time-scales

Bell, Cameron P. M.; Naylor, Tim; Mayne, N. J.; Jeffries, R. D.; Littlefair, S. P.

Abstract

We have derived ages for 13 young (<30 Myr) star-forming regions and find that they are up to a factor of 2 older than the ages typically adopted in the literature. This result has wide-ranging implications, including that circumstellar discs survive longer (≃ 10–12 Myr) and that the average Class I lifetime is greater (≃1 Myr) than currently believed. For each star-forming region, we derived two ages from colour–magnitude diagrams. First, we fitted models of the evolution between the zero-age main sequence and terminal-age main sequence to derive a homogeneous set of main-sequence ages, distances and reddenings with statistically meaningful uncertainties. Our second age for each star-forming region was derived by fitting pre-main-sequence stars to new semi-empirical model isochrones. For the first time (for a set of clusters younger than 50 Myr), we find broad agreement between these two ages, and since these are derived from two distinct mass regimes that rely on different aspects of stellar physics, it gives us confidence in the new age scale. This agreement is largely due to our adoption of empirical colour–Teff relations and bolometric corrections for pre-main-sequence stars cooler than 4000 K. The revised ages for the star-forming regions in our sample are: ∼2 Myr for NGC 6611 (Eagle Nebula; M 16), IC 5146 (Cocoon Nebula), NGC 6530 (Lagoon Nebula; M 8) and NGC 2244 (Rosette Nebula); ∼6 Myr for σ Ori, Cep OB3b and IC 348; ≃10 Myr for λ Ori (Collinder 69); ≃11 Myr for NGC 2169; ≃12 Myr for NGC 2362; ≃13 Myr for NGC 7160; ≃14 Myr for χ Per (NGC 884); and ≃20 Myr for NGC 1960 (M 36).

Citation

Bell, C. P. M., Naylor, T., Mayne, N. J., Jeffries, R. D., & Littlefair, S. P. (2013). Pre-main-sequence isochrones – II. Revising star and planet formation time-scales. Monthly Notices of the Royal Astronomical Society, 434(1), 806-831. https://doi.org/10.1093/mnras/stt1075

• Journal Article Type: Article
• Acceptance Date: Jun 12, 2013
• Online Publication Date: Jul 11, 2013
• Publication Date: Sep 1, 2013
• Deposit Date: Jun 16, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 434
• Issue: 1
• Pages: 806-831
• DOI: https://doi.org/10.1093/mnras/stt1075
• Keywords: Space and Planetary Science; Astronomy and Astrophysics