Empirical color correction to MIST and PARSEC isochrones on Gaia BR-RP and G-RP with benchmark open clusters

TL;DR

This paper develops empirical color correction functions for Gaia CMDs to improve the accuracy of cluster age estimates using MIST and PARSEC isochrones, validated on multiple clusters.

Contribution

It introduces empirically derived color correction functions for Gaia CMDs applied to MIST and PARSEC isochrones, enhancing age determination accuracy for stellar clusters.

Findings

Corrected isochrones align better with observed CMDs.

Age estimates match literature values after correction.

Metallicity estimates agree with spectroscopic data.

Abstract

Recent literature reports a color deviation between observed Gaia color-magnitude diagrams (CMDs) and theoretical model isochrone predictions, particularly in the very low-mass regime. To assess its impact on cluster age determination via isochrone fitting, we quantified the color deviations for three benchmark clusters, Hyades, Pleiades, and Praesepe, both for the Gaia color (BP-RP) and (G-RP). In general, the (G-RP) color deviations are smaller than the (BP-RP) ones. Empirical color correction functions based on these benchmarks are derived for the currently available MIST and PARSEC 1.2S isochrone models. Applying the correction functions to 31 additional open clusters and 3 moving groups results in a significantly improved alignment between the isochrones and observed CMDs. With our empirical corrections, isochrones provide age estimates consistent with literature values obtained through the spectral Lithium Depletion Boundary method, validating the effectiveness of our approach. The corresponding metallicities with PARSEC 1.2S also show a good agreement with the spectroscopic results. The empirical color correction function we present in this work offers a tool for a consistent age determination within the full mass range of stellar clusters using the isochrone fitting method.