Explanation of Thresholds
From the publications, I understand that Threshold 1 relates to the particle contrast relative to the background noise (S/N ratio), while Threshold 2 relates to the radial symmetry of the PSF. It is recommended to lower Threshold 1 for smaller masses (or increase it to suppress the contribution of small impurities). However, it remains unclear what the meaning of the numbers for these thresholds is, which makes it difficult to intuitively choose appropriate values for a given application.
My guess is that Threshold 1 takes the noise (i.e., fluctuation) of the background as a reference and discards any particles with a contrast below the noise. Threshold 2 is most likely related to the ellipticity of the point spread function, discarding any particles were the relative difference between the two axes exceeds the given values.
Any clarification on the mathematical basis for these thresholds would be appreciated. Thanks!
Thanks, but this does not really answer my question on the mathematical equations that govern the thresholds.