The assembly history of the nearest S0 galaxy NGC 3115 from its
  kinematics out to six half-light radii
  Using new and archival data, we study the kinematic properties of the nearest
field S0 galaxy, NGC 3115, out to $\sim6.5$ half-light radii ($R_\mathrm{e}$)
from its stars (integrated starlight), globular clusters (GCs) and planetary
nebulae (PNe). We find evidence of three kinematic regions with an inner
transition at $\sim0.2\ R_\mathrm{e}$ from a dispersion-dominated bulge
($V_\mathrm{rot}/\sigma <1$) to a fast-rotating disk ($V_\mathrm{rot}/\sigma
>1$), and then an additional transition from the disk to a slowly rotating
spheroid at $\sim2-2.5\, R_\mathrm{e}$, as traced by the red GCs and PNe (and
possibly by the blue GCs beyond $\sim5\, R_\mathrm{e}$). From comparison with
simulations, we propose an assembly history in which the original progenitor
spiral galaxy undergoes a gas-rich minor merger that results in the embedded
kinematically cold disk that we see today in NGC 3115. At a later stage, dwarf
galaxies, in mini mergers (mass-ratio $<$ 1:10), were accreted building-up the
outer slowly rotating spheroid, with the central disk kinematics largely
unaltered. Additionally, we report new spectroscopic observations of a sample
of ultra-compact dwarfs (UCDs) around NGC 3115 with the Keck/KCWI instrument.
We find that five UCDs are inconsistent with the general rotation field of the
GCs, suggesting an \textit{ex-situ} origin for these objects, i.e. perhaps the
remnants of tidally stripped dwarfs. A further seven UCDs follow the GC
rotation pattern, suggesting an \textit{in-situ} origin and, possibly a GC-like
nature.
