The Carnegie-Chicago Hubble Program. V. The Distances to NGC 1448 and
  NGC 1316 via the Tip of the Red Giant Branch
  The Carnegie-Chicago Hubble Program (CCHP) is re-calibrating the
extragalactic SN Ia distance scale using exclusively Population II stars. This
effort focuses on the Tip of the Red Giant Branch (TRGB) method, whose
systematics are entirely independent of the Population I Cepheid-based
determinations that have long served as calibrators for the SN Ia distance
scale. We present deep Hubble Space Telescope imaging of the low
surface-density and low line-of-sight reddening halos of two galaxies, NGC 1448
and NGC 1316, each of which have been hosts to recent SN Ia events.
Provisionally anchoring the TRGB zero-point to the geometric distance to the
Large Magellanic Cloud derived from detached eclipsing binaries, we measure
extinction-corrected distance moduli of 31.23 +/-0.04 (stat) +/- 0.06 (sys) mag
for NGC 1448 and 31.37 +/- 0.04 (stat) and +/- 0.06 (sys) mag for NGC 1316,
respectively, giving metric distances of 17.7 +/- 0.3 (stat) +/- 0.5 (sys) Mpc,
and 18.8 +/- 0.3 (stat) +/- 0.5 (sys) Mpc. We find agreement between our result
and the available Cepheid distance for NGC 1448; for NGC 1316, where there are
relatively few published distances based on direct measurements, we find that
our result is consistent with the published SN Ia distances whose absolute
scales are set from other locally-determined methods such as Cepheids. For NGC
1448 and NGC 1316, our distances are some of the most precise (and
systematically accurate) measurements with errors at 1.7 (2.8) % and 1.6 (2.7)
% levels, respectively.
