sobj Files

This kind of FITS file is output from SExtractor as described in Section 8.2.1. An sobj file consists of a primary header and an array of structures. The latter is saved as the first FITS extension. Use the IDL program mrdfits('sobjname.fit',1) as described in Section B.3 to access the object list. The primary header consists of the FITS standard keywords, and the following additional keywords:

HISTORY   


EPOCH 		                                               


OBJECT 		                                               


ORIGIN 		                                               


SEXIMASX 		IMAGE WIDTH (PIXELS)              


SEXIMASY 		IMAGE HEIGHT (PIXELS)                          


SEXSTRSY 		STRIP HEIGHT (LINES)                           


SEXIMABP 		FITS IMAGE BITPIX                              


SEXPIXS 		PIXEL SCALE (ARCSEC)                           


SEXSFWHM 		SEEING FWHM (ARCSEC)                           


SEXNNWF 		CLASSIFICATION NNW FILENAME                    


SEXGAIN 		GAIN (IN E- PER ADU)                           


SEXBKGND 		MEDIAN BACKGROUND (ADU)                        


SEXBKDEV 		MEDIAN RMS (ADU)                               


SEXBKTHD 		EXTRACTION THRESHOLD (ADU)                     


SEXCONFF 		CONFIGURATION FILENAME                         


SEXDETT 		DETECTION TYPE                                 


SEXTHLDT 		THRESHOLD TYPE                                 


SEXTHLD 		THRESHOLD                                      


SEXMINAR 		EXTRACTION MINIMUM AREA (PIXELS)               


SEXCONV 		CONVOLUTION FLAG                               


SEXCONVN 		CONVOLUTION NORM. FLAG                         


SEXCONVF 		CONVOLUTION FILENAME                           


SEXDBLDN 		NUMBER OF SUB-THRESHOLDS                       


SEXDBLDC 		CONTRAST PARAMETER                             


SEXCLN 		CLEANING FLAG                                  


SEXCLNPA 		CLEANING PARAMETER                             


SEXCLNST 		CLEANING OBJECT-STACK                          


SEXAPERD 		APERTURE DIAMETER (PIXELS)                     


SEXAPEK1 		KRON PARAMETER                                 


SEXAPEK2 		KRON ANALYSIS RADIUS                           


SEXAPEK3 		KRON MINIMUM RADIUS                            


SEXSATLV 		SATURATION LEVEL (ADU)                         


SEXMGZPT 		MAGNITUDE ZERO-POINT                           


SEXMGGAM 		MAGNITUDE GAMMA                                


SEXBKGSX 		BACKGROUND MESH WIDTH (PIXELS)                 


SEXBKGSY 		BACKGROUND MESH HEIGHT (PIXELS)                


SEXBKGFX 		BACKGROUND FILTER WIDTH                        


SEXBKGFY 		BACKGROUND FILTER HEIGHT                       


SEXPBKGT 		PHOTOM BACKGROUND TYPE                         


SEXPBKGS 		LOCAL AREA THICKNESS (PIXELS)                  


SEXPIXSK 		PIXEL STACKSIZE (PIXELS)                       


SEXFBUFS 		FRAME-BUFFER SIZE (LINES)                      


SEXISAPR 		ISO-APER RATIO                                 


SEXNDET 		NB OF DETECTIONS                               


SEXNFIN 		NB OF FINAL EXTRACTED OBJECTS                  


SEXNPARA 		NB OF PARAMETERS PER OBJECT

The object list consists of an array of structures: one element for each object. A single structure in this array has the following fields:

NUMBER               Object number


MAG_APER 		Aperture Magnitude


MAGERR_APER 		Uncertainty in same


BACKGROUND 		Local Background (ADU)


FLUX_MAX 		Peak Object Flux (ADU)


MU_MAX 		??


ISOAREA_IMAGE 		Isophotal Area of Object


X_IMAGE 		X-coordinate of object (FITS Coord + 1)


Y_IMAGE 		Y-coordinate of object (FITS Coord + 1)


FWHM_IMAGE 		Measuring the PSF


FLAGS 		Bitmask of SExtractor flags

Table C.1: Possible values for the FLAGS bitmask field in the raw object list structures.

Bit value	Tag Name	Meaning
1	NEIGHBORS	Not used with MAG_APER
2	BLENDED	Object was originally blended with another one.
4	SATURATED	At least one pixel of the object is saturated.
8	ATEDGE	The object is truncated (too close to an image boundary).
16	APINCOMPL	Object's aperture data are imcomplete or corrupted.
32	ISINCOMPL	Object's isophotal data are incomplete or corrupted.
64	DBMEMOVR	Memory overflow occured during deblending.
128	EXMEMOVR	Memory overflow occured during extraction.

The FLAGS values are described in the SExtractor documentation and are summarized in Table C.1.