On the Age Calibration of Open Clusters using Red Clump Stars

Abstract

In this study, we extend the dust-independent Hatzidimitriou (1991) relation between cluster age and $d_{B-R}$ color difference between the red giant branch (RGB) and red clump to younger cluster ages. We perform membership analysis on fourteen galactic open clusters using Gaia DR3 astrometry, then compute the difference in color of the RGB and red clump $d_{B-R}$ using Gaia photometry. We also compute $d_{B-R}$ for five fields surrounding Small Magellanic Cloud (SMC) clusters. We find that the trend derived from older clusters does not extrapolate to younger ages and becomes double-valued. We confirm that $d_{B-R}$ is independent of metallicity. Current stellar evolutionary isochrones do not quantitatively reproduce the trend and furthermore predict an increased color gap with a decrease in metallicity that is not echoed in the data. Integrated light models based on current isochrones exaggerate the color change over the $-0.5<$ [Fe/H] $<0$ interval at the few-percent level.

12 pages, 12 figures

References in corpus (12)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Early Data Release 3: Photometric content and validation
• Painting a portrait of the Galactic disc with its stellar clusters
• Updated parameters of 1743 open clusters based on Gaia DR2
• Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud
• Stellar Population Models and Individual Element Abundances I: Sensitivity of Stellar Evolution Models
• Physical parameters of 15 intermediate-age LMC clusters from modelling of HST colour-magnitude diagrams
• Chemical evolution of the Small Magellanic Cloud based on planetary nebulae
• Comparison of the Asteroseismic Mass Scale of Red Clump Giants with Photometric Mass Estimates
• Astrometric star-cluster membership probability: application to the case of M 37 with Gaia EDR3
• Individual element sensitivity for stellar evolutionary isochrones
• Chemically Peculiar Stars in Integrated Light Stellar Population Models and Local Group Galaxies