The ACS Survey of Galactic Globular Clusters XI: The Three-Dimensional
  Orientation of the Sagittarius Dwarf Spheroidal Galaxy and its Globular
  Clusters
  We use observations from the ACS study of Galactic globular clusters to
investigate the spatial distribution of the inner regions of the disrupting
Sagittarius dwarf spheroidal galaxy (Sgr). We combine previously published
analyses of four Sgr member clusters located near or in the Sgr core (M54, Arp
2, Terzan 7 and Terzan 8) with a new analysis of diffuse Sgr material
identified in the background of five low-latitude Galactic bulge clusters (NGC
6624, 6637, 6652, 6681 and 6809) observed as part of the ACS survey. By
comparing the bulge cluster CMDs to our previous analysis of the M54/Sgr core,
we estimate distances to these background features. The combined data from four
Sgr member clusters and five Sgr background features provides nine independent
measures of the Sgr distance and, as a group, provide uniformly measured and
calibrated probes of different parts of the inner regions of Sgr spanning
twenty degrees over the face of the disrupting dwarf. This allows us, for the
first time, to constrain the three dimensional orientation of Sgr's disrupting
core and globular cluster system and compare that orientation to the
predictions of an N-body model of tidal disruption. The density and distance of
Sgr debris is consistent with models that favor a relatively high Sgr core mass
and a slightly greater distance (28-30 kpc, with a mean of 29.4 kpc). Our
analysis also suggests that M54 is in the foreground of Sgr by ~2 kpc,
projected on the center of the Sgr dSph. While this would imply a remarkable
alignment of the cluster and the Sgr nucleus along the line of sight, we can
not identify any systematic effect in our analysis that would falsely create
the measured 2 kpc separation. Finally, we find that the cluster Terzan 7 has
the most discrepant distance (25 kpc) among the four Sgr core clusters, which
may suggest a different dynamical history than the other Sgr core clusters.
