The Distance of the Dark Matter Deficient Galaxy NGC1052-DF2
  We recently inferred that the galaxy NGC1052-DF2 has little or no dark matter
and a rich system of unusual globular clusters. We assumed that the galaxy is a
satellite of the luminous elliptical galaxy NGC1052 at ~20 Mpc, on the basis of
its surface brightness fluctuations (SBF) distance of $19.0 \pm 1.7$ Mpc, its
radial velocity of ~1800 km/s, and its projected position. Here we analyze the
color-magnitude diagram (CMD) of NGC1052-DF2, following the suggestion by
Trujillo et al. (2018) that the tip of the red giant branch (TRGB) can be
detected in currently available HST data and the galaxy is at ~13 Mpc. Using
fully populated galaxy models we show that the CMD is strongly influenced by
blends. These blends produce a "phantom" TRGB ~2 times brighter than the true
TRGB, which can lead to erroneous distance estimates ~1.4 times smaller than
the actual distance. We compare NGC1052-DF2 to model images as well as other
galaxies in our HST sample, and show that the large population of unblended RGB
stars expected for distances of ~13 Mpc is not detected. We also provide a new
distance measurement to NGC1052-DF2 that is free of calibration uncertainties,
by anchoring it to a satellite of the megamaser host galaxy NGC4258. From a
megamaser-TRGB-SBF distance ladder we obtain $D=18.7 \pm 1.7$ Mpc, consistent
with our previous measurement and with the distance to the elliptical galaxy
NGC1052.
