Type II Cepheids as stellar tracers and distance indicators

TL;DR

Type II Cepheids serve as reliable distance indicators and tracers of old stellar populations, with near-infrared observations enabling calibration of their Period-Luminosity relations and insights into galactic structure.

Contribution

This study calibrates the Period-Luminosity relations of Type II Cepheids using near-infrared data and demonstrates their effectiveness in tracing the structure and old stellar populations of the Galactic bulge.

Findings

Estimated a robust distance to the Galactic center.

Type II Cepheids trace spherical and ellipsoidal stellar distributions.

They effectively trace old, metal-poor, kinematically hot populations.

Abstract

Type II Cepheids are both useful distance indicators and tracers of old age stellar populations in their host galaxy. We summarize near-infrared observations of type II Cepheids in the Large Magellanic Cloud and discuss the absolute calibration of their Period-Luminosity relations. Combining with the near-infrared data for type II Cepheids in the Galactic bulge from the VISTA VVV survey, we estimated a robust distance to the Galactic center. We found that type II Cepheids trace the spherically symmetric spatial distribution with possible evidence of ellipsoidal structure, similar to RR Lyrae stars. Together with Gaia and VVV proper motions, type II Cepheids were found to trace the old, metal-poor, kinematically hot stellar populations in the Galactic bulge.