Impact of the low solar abundance on the ages of globular clusters

TL;DR

This study examines how adopting the low Solar abundance from Asplund et al. (2004) affects the estimated ages of globular clusters, revealing a roughly 10% increase that influences galaxy formation theories.

Contribution

It introduces new stellar models and isochrones calibrated with the Asplund et al. (2004) solar mixture, highlighting its impact on globular cluster age estimates.

Findings

Globular cluster ages increase by about 10% with the new solar abundance.

The revised ages suggest clusters may have formed before reionization.

Implications for galaxy formation models are significant.

Abstract

We present the result of our investigation on the impact of the low Solar abundance of Asplund and collaborators (2004) on the derived ages for the oldest star clusters based on isochrone fittings. We have constructed new stellar models and corresponding isochrones using this new solar mixture with a proper Solar calibration. We have found that the use of the Asplund et al. (2004) metallicity causes the typical ages for old globular clusters in the Milky Way to be increased roughly by 10\%. Although this may appear small, it has a significant impact on the interpretation for the formation epoch of Milky Way globular clusters. The Asplund et al. (2004) abundance may not necessarily threaten the current concordance cosmology but would suggest that Milky Way globular clusters formed before the reionization and before the main galaxy body starts to build up. This is in contrast to the current understanding on the galaxy formation.