We present three-dimensional kinematics of Sagittarius ( Sgr ) trailing tidal debris in six fields located 70-130 \arcdeg along the stream from the Sgr dwarf galaxy core .
The data are from our proper-motion ( PM ) survey of Kapteyn ’ s Selected Areas , in which we have measured accurate PMs to faint magnitudes in \sim 40 \arcmin \times 40 \arcmin fields evenly spaced across the sky .
The radial velocity ( RV ) signature of Sgr has been identified among our follow-up spectroscopic data in four of the six fields and combined with mean PMs of spectroscopically-confirmed members to derive space motions of Sgr debris based on \sim 15-64 confirmed stream members per field .
These kinematics are compared to predictions of the Law & Majewski ( 58 ) model of Sgr disruption ; we find reasonable agreement with model predictions in RVs and PMs along Galactic latitude .
However , an upward adjustment of the Local Standard of Rest velocity ( \Theta _ { LSR } ) from its standard 220 km s ^ { -1 } to at least 232 \pm 14 km s ^ { -1 } ( and possibly as high as 264 \pm 23 km s ^ { -1 } ) is necessary to bring 3-D model debris kinematics and our measurements into agreement .
Satisfactory model fits that simultaneously reproduce known position , distance , and radial velocity trends of the Sgr tidal streams , while significantly increasing \Theta _ { LSR } , could only be achieved by increasing the Galactic bulge and disk mass while leaving the dark matter halo fixed to the best-fit values from Law & Majewski ( 58 ) .
We derive low-resolution spectroscopic abundances along this stretch of the Sgr stream and find a constant [ Fe/H ] \sim -1.15 ( with \sim 0.5 dex scatter in each field – typical for dwarf galaxy populations ) among the four fields with reliable measurements .
A constant metallicity suggests that debris along the \sim 60 \arcdeg span of this study was all stripped from Sgr on the same orbital passage .