S-COSMOS MIPS-Ge GO2 Delivery
27May2007
14Aug2008 Added notice
H. Aussel + S-COSMOS team

0. IMPORTANT NOTICE

While working on the GO-3 SCOSMOS data, we have discovered a problem
with the fluxes of the distributed GO-2 deep and main catalogs. A
correction factor has been applied twice to all flux columns of both
catalogs. The affected columns are "fitflux", "fitbkg", "fluxaper",
"mesaper" and "corraper" in both catalogs. In order to retrieve the
correct values, the following correction should be applied: 

correct_flux = 1.32 * catalog_flux

The distributed images are not suffering from this problem.

Also please note that there is still some asteroid contamination in 
the Main catalog were the small number of repeat observations did not 
allow us to filter out the slow moving objects. Asteroid have been 
filtered out from the Deep catalog were numerous epochs were available.

I. Basic Information

Telescope:             Spitzer
PI:                    David B. Sanders
Program Title:         SCOSMOS
Program ID:            20070
MIPS Band :            24um
SSC Software Version:  S 13.2.0
See SSC website for S 13.2.0 data issues and Calibration.

These are the MIPS 24 maps and catalog resulting from the General
Observer Cycle 2 observations of the S-COSMOS program. Please refer to
Sanders et al. (astro-ph/0701318) for a discussion of the
observations. The current data product version is 1.1.

The directory contains:

mips_24_g02_cat.tbl			Main area catalog
mips_24_g02_sci_11.fits			Main area image
mips_24_g02_cov_11.fits			Main area coverage map
mips_24_g02_unc_11.fits			Main area uncertainty map

mips_24_g02_deep_cat.tbl		Deep area catalog
mips_24_g02_deep_sci_11.fits		Deep area image
mips_24_g02_deep_cov_11.fits		Deep area coverage map
mips_24_g02_deep_unc_11.fits		Deep area uncertainty map

Images and uncertainty images are in units of MJy/sr.
To convert the images in mJ, multiply them for the factor 0.141085553.

Note that the coverage map is somewhat unusual due to the large number
of asteroids that have been removed from these data.

Notes on Catalogs:
-----------------
The catalogs were produced in two passes. First, a detection pass was  
performed using the IDL implementation of DAOPHOT. Then aperture  
photometry and PSF-fitting photometry were performed on the  
detections in a 7x7 pixels subimage centered on the detection. The  
signal over noise on the peak pixel is given by the "pksn" catalog  
column. Neighboring sources were masked out, using a 3 pixel radius  
aperture. If no other sources were detected nearby, the number of  
pixels fitted is therefore 49. If other sources fall within this box,  
their corresponding pixels will be masked and the number of pixels  
used for the fit will be lower than 49. The catalog column "np" holds  
the number of pixels used.

The PSF fit photometry is determined by fitting a set of PSF build  
from the MIPS 24 PRF  ("Pixel Response Function") with the source  
position at different sub-pixel locations within the peak pixel,   
plus a constant background to the subimage. The "fitflux" and  
"fitbkg" catalog columns hold the values of the fitted source flux  
and background respectively. The "chi2" column contains the reduced  
chi-squared of the fit. Since the fit is done on background  
subtracted images, the "fitbkg" value should be close to zero.

Aperture photometry is performed on the same sub-image as the PSF- 
fitting photometry, so the aperture used is a square 7x7 aperture,  
with neighboring sources masked out, assuming a zero background.  The  
raw measurement if given by the "mesaper" column of the catalog.  The  
aperture photometry was then corrected to total fluxes using the MIPS  
24 PSF model. The correction factor is given by the "corrape" column.  
The total flux after aperture correction is given by the "fluxaper"  
column. The error on the flux aperture measurment is given by the  
"erraper" column.

For isolated point sources, fitflux and fluxaper should be equal. The  
catalogs have been cut at 0.06 mJy for the Deep, and 0.300 mJy for  
the Main. Users are invited to exercise caution with all sources but  
especially with low S/N ones (as tested by fluxaper/erraper). The  
number of pixels (np) is a good indication of blending. np = 49 for  
almost isolated sources. The lower, the most confused it is. Also,  
sources with fitflux very different from fluxaper should be treated  
with caution, as they may be extended, blended or spurious.


Catalogs columns are:
id       : Identification number of the source
ra       : Right Ascension, degree J2000
dec      : Declination, degree J2000
pksn     : peak signal/noise ratio
np       : number of pixels used for PSF fitting and aperture photometry
fitflux  : PSF fitted flux, mJy
fitbkg   : Derived background during PSF fitting (mJy) Should be close to zero
chi2     : Reduced chi square of the fit solution
mesaper  : Raw aperture measurment (mJy)
fluxaper : Aperture photometry flux, including aperture correction (mJy) given by the corraper column
err aper : Error on the flux aper (mJy)
corraper : Aperture correction factor
idmain   : ID of the counterpart in the Main (resp Deep) catalog. 0 if no counterparts
distm    : distance in arcsec to the counterpart, 99.99 if too far.