RR Lyrae stars as probes of the Milky Way structure and formation

TL;DR

This paper discusses how RR Lyrae stars serve as vital tools for understanding the Milky Way's structure, formation, and evolution, based on recent survey data and analysis of their distribution, metallicity, and populations.

Contribution

It provides new insights into the spatial distribution, metallicity, and multiple populations of RR Lyrae stars in the Milky Way and its satellite systems from the OGLE survey data.

Findings

Distribution of RRab stars extends to 40 kpc from Galactic Center

Identification of multiple stellar populations among RR Lyrae stars

Analysis of RR Lyrae stars in Sgr dwarf galaxy and M54 globular cluster

Abstract

RR Lyrae stars being distance indicators and tracers of old population serve as excellent probes of the structure, formation, and evolution of our Galaxy. Thousands of them are being discovered in ongoing wide-field surveys. The OGLE project conducts the Galaxy Variability Survey with the aim to detect and analyze variable stars, in particular of RRab type, toward the Galactic bulge and disk, covering a total area of 3000 deg^2. Observations in these directions also allow detecting background halo variables and unique studies of their properties and distribution at distances from the Galactic Center to even 40 kpc. In this contribution, we present the first results on the spatial distribution of the observed RRab stars, their metallicity distribution, the presence of multiple populations, and relations with the old bulge. We also show the most recent results from the analysis of RR Lyrae stars of the Sgr dwarf spheroidal galaxy, including its center, the globular cluster M54.