Type II Cepheids as stellar tracers and distance indicators
  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.
