The Age and Helium Abundance of the Galactic Bulge

TL;DR

This paper examines the challenges in determining the age and helium abundance of the Galactic bulge, highlighting observational degeneracies and proposing methods to resolve them for more accurate stellar population analysis.

Contribution

It identifies the degeneracy between age and helium abundance in observations and discusses strategies to disentangle these parameters in future studies.

Findings

Age and helium abundance can be observationally degenerate.

Assumptions about helium-metallicity relations can bias age estimates.

Methods like red giant branch bump analysis and direct measurements can resolve degeneracy.

Abstract

I discuss the age and helium abundance of the Galactic bulge stellar population. I present examples as to how age and helium abundance can be degenerate observationally, and thus, how unstated assumptions of the helium-metallicity relation can result in biased age-metallicity determinations. I summarise efforts to tackle this degeneracy using the red giant branch bump, forward modelling of microlensing selection effects, and direct mass and metallicity measurements of stars along the red giant branch. I make the case that the degeneracy between these two parameters can be resolved in the near future.