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| Paper: |
Kinematics of Stars Along the Sagittarius Trailing Tidal Tail and Constraints on the Milky Way Mass Distribution |
| Volume: |
458, Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way |
| Page: |
207 |
| Authors: |
Carlin, J. L. |
| Abstract: |
To date, models of the Sagittarius (Sgr) tidal debris streams have
been constrained by positions, distances, and radial velocities of
detected debris, but no systematic survey has addressed the tangential
velocities (derived from proper motions) of Sgr detritus. We present
three-dimensional kinematics of Sgr trailing tidal debris
in six fields located 70–130° 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 40′ × 40′ 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 15–64 confirmed
stream members per field. These kinematics are compared to predictions
of the Law & Majewski (2010) 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 (ΘLSR) from its standard 220 km
s-1 to at least 232 ± 14 km s-1 (and possibly as high as
264 ± 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 ΘLSR 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 (2010). |
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