Distance and mass of the NGC 253 galaxy group
  Two dwarf galaxies: WOC2017-07 and PGC 704814 located in the vicinity of the
nearby luminous spiral galaxy NGC 253 were observed with the Advanced Camera
for Surveys on the Hubble Space Telescope. Their distances of 3.62$\pm$0.18 Mpc
and 3.66$\pm$0.18 Mpc were derived using the tip of the red giant branch
method. These distances are consistent with the dwarf galaxies being members of
the NGC 253 group. Based on the radial velocities and projected separations of
seven assumed dwarf companions, we estimated the total mass of NGC 253 to be
$(8.1\pm2.6) 10^{11} M_{\odot}$, giving a total-mass-to-$K$-luminosity ratio
$M_{\rm orb}/L_K = (8.5\pm2.7) M_{\odot}/L_{\odot}$. A notable property of NGC
253 is its declined rotation curve. NGC 253 joins four other luminous spiral
galaxies in the Local Volume with declined rotation curves (NGC 2683, NGC 2903,
NGC 3521 and NGC 5055) that together have the low average
total-mass-to-luminosity ratio, $M_{\rm orb}/L_K = (5.5\pm1.1)
M_{\odot}/L_{\odot}$. This value is only $\sim$1/5 of the corresponding ratio
for the Milky Way and M 31.
