MOPEX User's Guide - IRSA

MOPEX User’s Guide
If Nimages is greater than or equal to Minimum Number of Images, then the outlier ε's are excluded
from calculating δ, but δ is applied to all the ε's.
Figure 8.21: The overlap of Image1 and Image2 is an area of four pixels with the following
pixel indices: k1= {36,37,38,39}; k2 = {0,1,2,3}, given that the first pixel has index = 0 and the
x-direction is scanned first.
8.6 PRF fitting in MOPEX
Final point source position and photometry estimation are performed for all point source
candidates on the detection list by module Source Estimate. For each point source candidate the
data in the input images are fit with the Point Response Function (PRF; see §8.7). For the multiframe
point source extraction the fitting is performed simultaneously in all input images.
The size of the fitting area is determined by the parameters Fitting Area X and Fitting Area Y, if
they are given. If they are not given, the Fit Radius module should have been run to estimate the
size of the fitting area for each detection. This is the preferable method of setting the size of the
fitting areas, since the size will vary with the brightness of the point sources brighter sources in
general will have larger fitting areas. The user should be aware, however, that the Fit Radius
module is not foolproof and may produce erroneous results.
The goal of the fitting is to estimate the fluxes and to refine the positions of the point sources. The
n-th point source is characterized by the flux f(n) and mosaic position R(n) (see Figure 8.22). If
Basic Concepts in MOPEX 208
P RF fitting in MOPEX