English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

RR Lyrae stars (RRLs) are tracers of the Milky Way's fossil record, holdingvaluable information on its formation and early evolution. Owing to the highinterstellar extinction endemic to the Galactic plane, distant RRLs lying atlow Galactic latitudes have been elusive. We attained a census of 1892high-confidence RRLs by exploiting the near-infrared photometric database ofthe VVV survey's disk footprint spanning $\sim$70$^\circ$ of Galacticlongitude, using a machine-learned classifier. Novel data-driven methods wereemployed to accurately characterize their spatial distribution using sparselysampled multi-band photometry. The RRL metallicity distribution function (MDF)was derived from their $K_s$-band light curve parameters using machine-learningmethods. The MDF shows remarkable structural similarities to both thespectroscopic MDF of red clump giants and the MDF of bulge RRLs. We model theMDF with a multi-component density distribution and find that the numberdensity of stars associated with the different model components systematicallychanges with both the Galactocentric radius and vertical distance from theGalactic plane, equivalent to weak metallicity gradients. Based on theconsistency with results from the ARGOS survey, three MDF modes are attributedto the old disk populations, while the most metal-poor RRLs are probably halointerlopers. We propose that the dominant [Fe/H] component with a mean of $-1$dex might correspond to the outskirts of an ancient Galactic spheroid orclassical bulge component residing in the central Milky Way. The physicalorigins of the RRLs in this study need to be verified by kinematicalinformation.

A Near-infrared RR Lyrae census along the southern Galactic plane: the Milky Way's stellar fossil brought to light