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Surface Brightness Fluctuations (SBF)
average flux is then f= s2/g
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e.g. at a radius of 1 arcmin in the bulge of M31, we see I surface brightness of g=16 mag sec-2
- assume no readout noise, perfect seeing
- irreduceable mottling in 1 pixels gives s=19.5 mag (about 4% of the mean)
- magnitude corresponding to f: mI = 2x19.5-16.0 = 23.0 mag
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MI - (V-I) zero point and slope universal (consistent with theory)
Notes: