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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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