1. Distance & kernel controls
Distance scale factor s = D / D₀
s = 1 uses the catalog distance baked into the ROTMOD file.
Move s to mimic distance shifts while keeping the QDS kernel fixed.
× current D₀
QDS kernel parameters (fixed for this lab)
These are the same (α, λc) used across DDO154/NGC2403 in the rotation evidence tests.
Current fit metrics (this s, this kernel)
Points used
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Rows with finite r, Vobs, err > 0
χ² baseline
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Baryons only (scaled with s)
χ² QDS
–
Baryons × [1 + α e-r/λc]
Δχ² (QDS − base)
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Negative = QDS better; positive = worse
χ² per point (base / QDS)
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Quick feel for fit quality
Waiting for data…
2. Distance scan (QDS view)
When you hit Scan, we sweep s from 0.6 → 1.4 in 0.01 steps,
keep α and λc fixed, and find the s that minimises χ²QDS(s).
This is “where QDS would like NGC3198 to sit” under these assumptions.
Best s (QDS)
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Distance factor D / D₀
χ² QDS @ best s
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Absolute χ² at that distance factor
Δχ² vs s = 1
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QDS(s*) − QDS(s = 1)
No scan run yet. Hit Scan distance range above to let QDS have an opinion.