Around the Spindle galaxy: the dark halo mass of NGC3115
  We report observations of five dwarf galaxies in the vicinity of the luminous
S0 galaxy NGC 3115 performed with the Advanced Camera for Surveys on the Hubble
Space Telescope. Their distances determined via the Tip of the Red Giant Branch
are: 10.05 Mpc (UGCA 193), 9.95 Mpc (KKSG 17), 10.13 Mpc (2MASX-J0957-0915),
10.42 Mpc (2dFGRS-TGN218Z179) and 11.01 Mpc (KKSG 19). With their typical
distance error of about 0.75 Mpc all the five dwarfs are consistent to be true
satellites of the host galaxy NGC 3115 (10.2$\pm$0.2 Mpc). Using the DESI
Legacy Imaging Surveys we also found 5 new probable dwarf satellites of
NGC3115, as well as 4 new probable members of the neighboring group around NGC
3521 situated 3 Mpc away from the NGC 3115 group. Based on the radial
velocities and projected separations of 10 dwarf companions, we derived the
total (orbital) mass of NGC 3115 to be (4.89$\pm$1.48) $10^{12}$ $M_{\odot}$.
The ratio of the total mass-to-K-luminosity of NGC 3115 is (50$\pm$15)
$M_\odot/L_\odot$, which is typical for the early-type luminous galaxies.
