Metallicity Distribution of Galactic Halo Field RR Lyrae, and the Effect of Metallicity on their Pulsation Properties

TL;DR

This study analyzes a large sample of Galactic RR Lyrae stars to understand their metallicity distribution and how metallicity influences their pulsation properties, especially in infrared light curves.

Contribution

It provides the largest homogeneous spectroscopic dataset of RR Lyrae metallicities and investigates their distribution and pulsation dependence on metallicity.

Findings

Metallicity distribution of Galactic Halo RR Lyrae stars characterized.

Correlation between metallicity and pulsation properties established.

Insights into the Oosterhoff dichotomy in globular clusters gained.

Abstract

We present our analysis of a large sample (over 150k) of candidate Galactic RR Lyrae (RRL) stars for which we derived high quality photometry at UV, optical and infrared wavelengths, using data from publicly available surveys. For a sub-sample of these stars (~2,400 fundamental mode field RRLs) we have measured their individual metallicity using the Delta S method, resulting in the largest and most homogeneous spectroscopic data set collected for RRLs. We use this sample to study the metallicity distribution in the Galactic Halo, including the long-standing problem of the Oosterhoff dichotomy among Galactic globular clusters. We also analyze the dependence of their pulsation properties, and in particular the shape of their infrared light curves, from their [Fe/H] abundance.