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| Paper: |
Accurate Stellar Kinematics at Faint Magnitudes: Application to
the Boötes I Dwarf Spheroidal Galaxy |
| Volume: |
458, Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way |
| Page: |
375 |
| Authors: |
Koposov, S. |
| Abstract: |
We develop, implement and characterise an enhanced data reduction
approach which delivers precise, accurate, radial velocities from
moderate resolution spectroscopy with the fibre-fed
VLT/FLAMES+GIRAFFE facility. The repeated measurements let us reliably calibrate our individual
velocity errors (0.2 ≤ δV ≤ 5 km s-1) and directly
detect stars with variable radial velocities.
We show, by application to the Boötes I dwarf spheroidal, that the intrinsic
velocity dispersion of this system is significantly below 6.5 km s-1 reported
by previous studies. Our data favor a two-population model of Boötes I, consisting
of a majority ‘cold’
stellar component, with velocity dispersion 2.4+0.9–0.5 km s-1,
and a minority ‘hot’ stellar component, with velocity dispersion
∼ 9 km s-1, although we can not completely rule out a single component
distribution with velocity dispersion 4.6+0.8–0.6 km s-1. |
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