Building on the Past: A New Approach to the Oosterhoff Dichotomy with RR Lyrae

The double role of RR Lyrae (RRL) stars as tracers of ancient merging events and distance indicators is key to investigating the history of the Milky Way (MW). Their presence in the Galactic Halo and Galactic Globular Clusters (GGCs) allows us to trace interactions with satellite galaxies. These properties have led us to investigate the origin of the Oosterhoff dichotomy, focusing on its association with ancient merging events. In our previous work, we considered samples of RRL in GGCs and field RRL from Gaia DR3 together with distances and photometric metallicities based on the literature. Here we present our new results on this subject based on several improvements: i) a significantly larger number of field RR Lyrae used to investigate the Oosterhoff dichotomy possessing the position and velocity information needed to calculate the integral of motion;ii) more accurate distance estimates using new MG-[Fe/H] and Period-Wesenheit-Metallicity (PWZ) relations derived from literature data and high-resolution spectroscopic surveys such as GALAH (DR4) and APOGEE (DR17); iii) more accurate photometric metallicities.