Zwicky Transient Facility and Globular Clusters: The RR Lyrae gri-Band
  Period-Luminosity-Metallicity and Period-Wesenheit-Metallicity Relations
  Based on time-series observations collected from Zwicky Transient Facility
(ZTF), we derived period-luminosity-metallicity (PLZ) and
period-Wesenheit-metallicity (PWZ) relations for RR Lyrae located in globular
clusters. We have applied various selection criteria to exclude RR Lyrae with
problematic or spurious light curves. These selection criteria utilized
information on the number of data points per light curve, amplitudes, colors,
and residuals on the period-luminosity and/or period-Wesenheit relations. Due
to blending, a number of RR Lyrae in globular clusters were found to be
anomalously bright and have small amplitudes of their ZTF light curves. We used
our final sample of ~750 RR Lyrae in 46 globular clusters covering a wide
metallicity range (-2.36 < [Fe/H] < -0.54 dex) to derive PLZ and PWZ relations
in gri bands. In addition, we have also derived the period-color-metallicity
(PCZ) and for the first time, the PQZ relations where the Q-index is
extinction-free by construction. We have compared our various relations to
empirical and theoretical relations available in literature, and found a good
agreement with most studies. Finally, we applied our derived PLZ relation to a
dwarf galaxy, Crater II, and found its true distance modulus should be larger
than the most recent determination.
