Quantifying Systematic Age Discrepancies in Very Young Star Clusters

Guzman, J, Murphy, JW, Beasor, E ORCID: 0000-0003-4666-4606, Dalcanton, JJ, Smith, N, Aghakhanloo, M, Williams, BF and Barrientos, AF (2026) Quantifying Systematic Age Discrepancies in Very Young Star Clusters. The Astrophysical Journal, 1008 (1). ISSN 0004-637X

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Abstract

We infer the ages of three young stellar clusters—NGC 2004, NGC 7419, and NGC 2100—using Stellar Ages, a statistical algorithm designed to infer stellar population properties from color–magnitude diagrams. Recent studies have revealed emerging inconsistencies in the inferred ages of very young (�50 Myr old) stellar clusters.
Here, we identify and quantify two distinct discrepancies. First, ages inferred from red supergiants (RSGs) are systematically older—by about a factor of 4—than those inferred from bright blue stars, with a median age offset of log (t/yr) = 0.60 ± 0.06 dex 10 (tB ≈ tRSG/4.0). Second, given the observed numbers of RSGs and bright blue stars, there is a pronounced deficit of lower-mass main-sequence stars relative to expectations from a standard initial mass function. Although these discrepancies resemble those reported for intermediate-age clusters, their magnitude and character suggest that they are unique to the evolution of massive stars. Together, these results highlight population-level inconsistencies with single-star evolutionary models and underscore the need to consider multiple evolutionary tracers when age-dating young clusters. By combining individual stellar ages with population-wide constraints, our approach refines prior work on cluster age determinations and provides new insight into massive star evolution and the interpretation of cluster demographics.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	IOP Publishing
Date of acceptance:	21 July 2026
Date of first compliant Open Access:	24 September 2026
Date Deposited:	24 Sep 2026 14:49
Last Modified:	24 Sep 2026 14:49
DOI or ID number:	10.3847/1538-4357/ae8f32
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29531

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