MOPEX Online Manual
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APEX Modules: Bright Detect
Output Directory Keyword: OUTPUT_DIR (apex_1frame.pl); COADDER_DIR (apex.pl)
Default Output Directory: <output_dir> (apex_1frame.pl); <output_dir>/Coadd (apex.pl)
Depends on: Input Files
PURPOSE
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This module provides a different kind of detection table than Detect . It includes
shape information about the detections, but it does not record the
blends, so in general it cannot replace Detect. It also
produces a mask image (=1 on the detections). This can be used to
mask the brightest detections before running Detect.
INPUTS
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Same as Detect.
PARAMETER BLOCK
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Same as Detect
OUTPUTS
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Table (*_detect_bright.tbl): A detection list with shape information.
FITS file (*_detect_bright_mask.fits) A mask image showing the segmentation level of detected clusters.
For multi-frame Apex, these are in the CoAdd subdirectory.
DISCUSSION
The bright detect list created by this module provides information about the shapes of the detections. The shape parameters are mostly clear from the column names. The shape parameter Linearity is 0.25 * (Perimeter length) / sqrt(No. pixels). Below is an example of the detection table:\char comment = Output from DETECT, version 4.00 \char Date-Time = Wed Feb 4 12:12:34 2004 \char comment = dlimage library version 2.00 \char FITS_In_Filename = apex_small/Coadd/coadd_Tile_001_Image_minback.fits \char FITS_Out_Filename = apex_small/Coadd/coadd_Tile_001_Image_detect_bright_mask.fits \char Sigma_In_Filename = apex_small/Coadd/coadd_Tile_001_Unc.fits \char Bright_Table_Out_Filename = apex_small/Coadd/coadd_Tile_001_Image_detect_bright.tbl \float Tile_OffsetX = 0 \float Tile_OffsetY = 0 \int Peaks_Radius = 1 \char CoverageMap_Filename = apex_small/Coadd/coadd_Tile_001_Cov.fits \float Min_Coverage = 2 \float Effective_Threshold = 0.259142 \int Extended_Object_Area = 200 \int Max_Segmentation_Level = 50 \int Detection_Max_Area = 1000 \int Detection_Min_Area = 30 \int N_Edge = 0 \float Detection_Threshold = 6 \char Input_Type = image_input \char Output_Type = centroids_and_pixels_output \char Neighbor_Type = sides_only \char Threshold_Type = peak \int Number_Of_Detections = 118 srcid| x | delta_x | y | delta_y | delta_xy | flux | delta_flux| maj_ax | delta_maj| min_ax | delta_min| elongation| ellipticity| theta | delta_theta| n_pixels| perimeter| linearity| | i |r | r |r | r | r | r | r | r | r | r | r | r | r | r | r | i | i | r | 1 6.292e+02 6.751e-02 2.552e+01 7.353e-02 3.333e-02 8.223e+02 1.407e+01 3.118e+00 7.856e -02 2.515e+00 6.159e-02 1.240e+00 1.934e-01 5.636e+01 5.636e+01 332 94 1.290e+00 2 1.493e+02 1.350e-02 3.395e+01 1.430e-02 -4.271e-03 3.814e+03 2.266e+01 1.553e+00 1.465e -02 1.471e+00 1.312e-02 1.056e+00 5.289e-02 -6.515e+01 -6.063e+01 278 132 1.979e+00 3 1.232e+03 3.253e-02 3.493e+01 3.006e-02 1.101e-03 3.814e+02 7.638e+00 1.118e+00 3.354e -02 1.020e+00 2.893e-02 1.095e+00 8.712e-02 1.720e+01 4.057e+01 70 46 1.375e+00
The bright detect mask marks detections with integer values equal to the highest segmentation level (iteration) reached, and non-detection pixels with 0.
Bright Detect can provide useful information as an adjunct to the normal Detect. In this case, set the available parameters to the same as those used for Detect, but be aware that because it does not include blend parameters, it cannot replace Detect for source extraction.
Advanced users could use this to try to mask out the brightest
sources before running Detect. Set the Detection
Threshold to a high value. Set
use_bright_object_mask = 1 in the Apex namelist. This tells Detect to mask out the bright
detections. Note: This feature has not been well-tested and users
should exercise caution.
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