The Metallicity Gradient of the Old Galactic Bulge Population

TL;DR

This paper investigates the presence and detectability of metallicity gradients in the Galactic Bulge using RR Lyrae stars, analyzing whether current data quality allows for identifying small gradients to inform galaxy formation models.

Contribution

It assesses the sensitivity of current RR Lyrae data to small metallicity gradients and discusses implications for Galactic Bulge formation theories.

Findings

Current data can detect gradients larger than a certain threshold.

No significant metallicity gradient was found within the data's sensitivity.

The study sets limits on the gradient magnitude based on data quality.

Abstract

Understanding the structure, formation and evolution of the Galactic Bulge requires the proper determination of spatial metallicity gradients in both the radial and vertical directions. RR Lyrae pulsators, known to be excellent distance indicators, may hold the key to determining these gradients. Jurcsik & Kovacs (1996) has shown that RR Lyrae light curves and the phase difference of their Fourier decomposition, {\phi}31, can be used to estimate photometric metallicities. The existence of galactic bulge metallicity gradients is a currently debated topic that would help pinpoint the Galaxy's formation and evolution. A recent study of the OGLE-III Galactic Bulge RR Lyrae Population by Pietrukowicz et al. (2012) suggests that the spatial distribution is uniform. We investigate how small a gradient would be detectable within the current S/N levels of the present data set, given the random and systematic errors associated with the derivation of a photometric metallicity versus spatial position relationship.