Publication Date:
2015-08-24
Description:
The mean absolute extinction towards the central parsec of the Milky Way is A K ~= 3 mag, including both foreground and Galactic Centre dust. Here we present a measurement of dust extinction within the Galactic old nuclear star cluster (NSC), based on combining differential extinctions of NSC stars with their l proper motions along Galactic longitude. Extinction within the NSC preferentially affects stars at its far side, and because the NSC rotates, this causes higher extinctions for NSC stars with negative l , as well as an asymmetry in the l -histograms. We model these effects using an axisymmetric dynamical model of the NSC in combination with simple models for the dust distribution. Comparing the predicted asymmetry to data for ~7100 stars in several NSC fields, we find that dust associated with the Galactic Centre mini-spiral with extinction A K ~= 0.15–0.8 mag explains most of the data. The largest extinction A K ~= 0.8 mag is found in the region of the Western arm of the mini-spiral. Comparing with total A K determined from stellar colours, we determine the extinction in front of the NSC. Finally, we estimate that for a typical extinction of A K ~= 0.4 the statistical parallax of the NSC changes by ~0.4 per cent.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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