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README file for the GALEX/COSMOS EM-photometry catalog, version 3 
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Note: version 3 is the first released version

This catalog was created using u*-band priors and the EM-algorithm.
Appropriate references for a description of the method are:

Guillaume, M., Llebaria A., Aymeric, D., Arnouts, S., & Milliard, B. 2006,
Proceedings of the SPIE, Volume 6064, pp. 332-341

This is the current reference, and contains all the basics of the method
and algorithm.  A more specific reference for this catalog will be
available soon.

Zamojski, Arnouts, Vibert, Schiminovich & Milliard (2008, in preparation)


The algorithm was run on the four NUV and the four FUV GALEX images covering
the COSMOS field.  It was run on the "-int" images (intensity maps) obtained
as a product of the GALEX pipeline processing, version 1.61.

The u*-band mosaic image and SExtractor catalog used as priors in this run
were generously provided by Henry McCracken (IAP) and are based on CFHT-u*
observations of the COSMOS field.  These are NOT included with the release.
People interested in the priors should contact both Henry and myself for
more information.


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Description of the columns
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Column 1 - Number:  This is the ID of the object in the u*-band prior
	catalog.  This is NOT the same as the ID in the general COSMOS
	photometry catalog.

Column 2,3 - Ra & Dec (in degrees)

Column 4,5 - Image from which the photometry was measured.
	(GALEX covers the COSMOS field in 4 pointings)

Column 6,7,8 & 9 -  Position of the object in the NUV and FUV images.
	(in pixels;  1 pix ~ 1.5")

Column 10,11 -  Measured background around the object (in counts/s).

Column 12,13 -  Measured flux of the object (in counts/s).

Column 14,15 -  Error in the flux measurement (counts/s).

Column 16,17 - AB-magnitude corresponding to the measured flux.

Column 18,19 - Magnitude error.

Column 20 -  u*-band magnitude used as the prior magnitude to start
	the iterative algorithm.  This is a MAG_AUTO with additional
	deblending, and can differ from the u*-band aperture magnitude
	in the general COSMOS photometry catalog.

Column 21, 22 -  NUV and FUV mask flags.  0 means ok.  1 means that
	the photometry of the object could be problematic due to either
	a nearby bright object, or image defects.

Column 23 -  The SExtractor CLASS_STAR from the u*-band prior
	catalog.  Objects with a CLASS_STAR > 0.8 were modeled
	with a simple PSF whereas the ones with a CLASS_STAR < 0.8
	were modeled with a profile based on their u*-band image
	convolved with the GALEX PSF.

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Written by Michel Zamojski, June 5th, 2008 (SSC)