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<strong>MOPEX</strong> User’s <strong>Guide</strong><br />
Minimize Ftol Success: (float) Termination criterion for the relative change in χ 2 / dof to<br />
achieve after Chi Threshold is reached.<br />
Dithe r Pixel Fraction: (float) See §8.6: PRF Fitting in <strong>MOPEX</strong>.<br />
Dither Flux Fraction: (float) See §8.6: PRF Fitting in <strong>MOPEX</strong>.<br />
Deblend Dithe r Pixe l Fraction: (float) Same as Dither Flux Fraction but applied during<br />
active deblending.<br />
*Background_Fit: (switch) Switch on (= 1) to fit a constant background under the point<br />
source in the fitting area. Default is off (= 0).<br />
Random_Fit: (switch) Switch on (= 1) to give the minimization routine a random start, so<br />
that the results of fitting on the same set of data will not be identical for every run.<br />
Chi2_Improvement: (float) Acceptable change in χ 2 / dof for incremented number of point<br />
sources in active deblending.<br />
*PRF ResampleX, Y Factor: (int) Ratio of the input image pixel size to the PRF pixel size.<br />
*Normalization Radius: (int) PRF flux is normalized within this radius (in PRF pixels). By<br />
default, the PRF is normalized to the whole PRF array.<br />
*Max Shift X, Y: (float) User List Mode only. Maximum distance in data pixels from the<br />
input position for a successfully fitted source position. If greater than Max Shift away from<br />
the user-supplied position, the source is given the letter "O" in the deblend column (for<br />
"Outside"), along with any other letter flags.<br />
*Angular Distance: (float) User List mode only. The maximum angular distance (arcsec)<br />
used to identify the nearby sources for simultaneous fitting. If it is not given then the script<br />
will look for the Spitzer keywords "INSTRUME" and "CHNLNUM" in the input FITS<br />
header and the value gets set as follows: INSTRUME = "MIPS" and CHNLNUM = 1:<br />
Angular_Distance = 6. INSTRUME = "MIPS" and CHNLNUM = 2: Angular_Distance =<br />
18. INSTRUME = "IRAC": Angular_Distance = 2 for all four channels. If the script is<br />
unable to set a value, the default is 0.0.<br />
*Use_Photerr_for_SNR: (switch) Options for how the signal-to-noise ratio (SNR) of the<br />
fitted source can be estimated. These are approximations to the flux SNR, distinct from the<br />
formal flux uncertainty from the fit, delta_flux, which is also output. The SNR choices are<br />
Point Source Extraction (APEX) 148<br />
APEX Modules
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