SExtractor Draft - METU Astrophysics

21Figure 3: A schematic diagram of the method used to deblend a composite object. The areaprofile of the object (smooth curve) can be described in a tree-structured way (thick lines).The decision to regard or not a branch as a distinct object is determined according to itsrelative integrated intensity (tinted area). In that case above, the original object shall split intotwo components A and B. Remaining pixels are assigned to their most credible “progenitors”afterwards.Centroid error (pixels)0.40.20-0.2-0.4Centroidm=21m=19m=15m=11-0.2MagnitudeMagnitude error-0.100.10.20 5 10 15 20 25 30Separation (pixels)Figure 4: Centroid and corrected isophotal magnitude errors for a simulated 19 th magnitudestar blended with a 11, 15, 19 and 21 th mag. companion as a function of distance (expressed inpixels). Lines stop at the left when the objects are too close to be deblended. The dashed verticalline is the theoretical limit for unsaturated stars with equal magnitudes. In the centroid plot,the arrow indicates the direction of the neighbour. The simulation assumes a 1 hour exposurewith the CERGA telescope on a IIIaJ plate and Moffat profiles with a seeing FWHM of 3 pixels(2 ”).