Concerning the Classical Cepheid VIc Wesenheit Function's Strong
  Metallicity Dependence
  Evidence is presented which supports findings that the classical Cepheid VIc
period-Wesenheit function is relatively insensitive to metallicity. The
viability of a recently advocated strong metallicity dependence was evaluated
by applying the proposed correction (gamma=-0.8 mag/dex) to distances
established for the Magellanic Clouds via a Galactic VIc Wesenheit calibration,
which is anchored to ten nearby classical Cepheids with measured HST
parallaxes. The resulting gamma-corrected distances for the Magellanic Clouds
(e.g., SMC, mu(0,gamma)~18.3) are in significant disagreement with that
established from a mean of >300 published estimates (NED-D), and a universal
Wesenheit template featuring eleven delta Scuti, SX Phe, RR Lyrae, and Type II
Cepheid variables with HST/Hipparcos parallaxes. Conversely, adopting a null
correction (i.e., gamma=0 mag/dex) consolidates the estimates. In tandem with
existing evidence, the results imply that variations in chemical composition
among Cepheids are a comparatively negligible source of uncertainty for
W(VIc)-based extragalactic distances and determinations of H_0. A new approach
is described which aims to provide additional Galactic Cepheid calibrators to
facilitate subsequent assessments of the VIc Wesenheit function's relative
(in)sensitivity to abundance changes. VVV/UKIDSS/2MASS JHKs photometry for
clusters in spiral arms shall be employed to establish a precise galactic
longitude-distance relation, which can be applied in certain cases to determine
the absolute Wesenheit magnitudes for younger Cepheids.
