Fig. 6.
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Example of the process from data to fitted model. Panel a: data used for the model, a two-dimensional histogram showing number density consisting of 1 396 320 stars. Panel b: initial background. Panel c: data/initial background. Panel d: extracted spiral perturbation. Panel e: initial fit spiral. Panel f: final background. Panel g: data/final background. Panel h: best fit spiral. Panel i: residuals as computed as: Data (panel a) – Best fit (panel h). See text for details on individual panels. This example consists of stars with 8.4 < R/kpc < 10.4 and 165° < ϕ < 195°.
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