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We present a method for fitting orbit-superposition models to the kinematics of discrete stellar systems when the available stellar sample has been filtered by a known selection function. The fitting method can be applied to any model in which the distribution function is represented as a linear superposition of basis elements with unknown weights. As an example, we apply it to Fritz et al.s kinematics of the innermost regions of the Milky Ways nuclear stellar cluster. Assuming spherical symmetry, our models fit a black hole of mass $M_bullet=(3.76pm0.22)times10^6,M_odot$, surrounded by an extended mass $M_star=(6.57pm0.54)times10^6,M_odot$ within 4 pc. Within 1 pc the best-fitting mass models have an approximate power-law density cusp $rhopropto r^{-gamma}$ with $gamma=1.3pm0.3$. We carry out an extensive investigation of how our modelling assumptions might bias these estimates: $M_bullet$ is the most robust parameter and $gamma$ the least. Internally the best-fitting models have broadly isotropic orbit distributions, apart from a bias towards circular orbits between 0.1 and 0.3 parsec.
We present new MMT/Hectochelle spectroscopic measurements for 257 stars observed along the line of sight to the ultra-faint dwarf galaxy Triangulum II. Combining with results from previous Keck/DEIMOS spectroscopy, we obtain a sample that includes 16
Studies of the Galactic Centre suggest that in-situ star formation may have given rise to the observed stellar population near the central supermassive black hole (SMBH). Direct evidence for a recent starburst is provided by the currently observed yo
We model the effects of collisions and close encounters on the stellar populations observed in the Milky Way nuclear stellar cluster (NSC). Our analysis is based on $N$-body simulations in which the NSC forms by accretion of massive stellar clusters
Using simulations of box/peanut- (B/P-) shaped bulges, we explore the nature of the X-shape of the Milky Ways bulge. An X-shape can be associated with a B/P-shaped bulge driven by a bar. By comparing in detail the simulations and the observations we
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. This facility, with appropriate care,