S-COSMOS Overview

S-COSMOS is a deep infrared imaging survey carried out with the Spitzer Space Telescope. The survey covers the entire 2 square degrees of the Cosmic Evolution Survey (COSMOS) field. The S-COSMOS and COSMOS projects are closely coupled; therefore, their data are served as one large COSMOS Archive using IRSA's general search service, Atlas. S-COSMOS is part of the Spitzer Legacy Program. The data products released are part of the Spitzer General Observer Cycle 2 (GO2) program, including predominantly IRAC products (images and catalog). MIPS data include shallow images/catalogs covering the entire COSMOS field. There are also deep MIPS images covering only a test field of 0.16 sq. degrees for the upcoming GO3 program. The GO3 products will become public in September 2008.

S-COSMOS MIPS 24um (GO2) Photometry Catalog Definitions

Gator serves 3 S-COSMOS MIPS 24um Photometry Catalogs:

The definitions below are only for the G02 MIPS 24um MAIN and DEEP Photometry Catalogs, June 2007; column descriptions for the GO3 24um catalog (Oct 2008) can be found here.

Aug. 2008: 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 fluxes columns of both catalogs. The affected columns are "fitflux", "fitbkg", "fluxaper", "mesaper" and "corraper" of 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.

Please refer to the MIPS 24um data delivery README file for general information on S-COSMOS catalogs and images, as well as a detailed information on the catalogs in the "Notes on Catalogs" section. Below is a compact version of that section:

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. The aperture photometry was corrected to total fluxes using the MIPS 24 PSF model. Both the raw aperture measurement (mesaper) , the corrected aperture measurement (fluxaper) and the PSF-fitting fluxes (fitflux) are provided here. 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 encouraged 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. Also, sources with fit_flux very different from fluxaper should be treated with caution, as they may be extended, blended or spurious.

The column descriptions can be found below.

Column Name Data Type Units Description
id integer n/a Identification number of the source
ra float degrees Right Ascension, degree J2000
dec float degrees Declination, degree J2000
pksn float n/a Peak signal/noise ratio
np integer n/a Number of pixels used for PSF fitting and aperture photometry. np=49 for isolated sources. The lower the number, the more blended the source is.
fitflux float mJy [milli-Jansky] PSF fitted flux. The PSF fit photometry is determined by fitting a set of PSFs built from the MIPS 24 PRF ("Pixel Response Function") to the source position at different sub-pixel locations within the peak pixel, plus a constant background to the subimage. The "fitflux" is the value of the fitted source flux. (Aug. 2008: See IMPORTANT NOTICE regarding flux)
fitbkg float mJy/pix [milli-Jansky/pixel] Background derived during PSF fitting. The PSF fit photometry is determined by fitting a set of PSF, built 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 "fitbkg" is the value of the background. (Aug. 2008: See IMPORTANT NOTICE regarding flux)
chi2 float n/a Reduced chi square of the fit solution
mesaper float mJy [milli-Jansky] Raw aperture measurement (a 7x7 pixel box, without aperture correction). 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. (Aug. 2008: See IMPORTANT NOTICE regarding flux)
fluxaper float mJy [milli-Jansky] Aperture photometry flux, including aperture correction. 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 flux 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. (Aug. 2008: See IMPORTANT NOTICE regarding flux)
erraper float mJy [milli-Jansky] The total flux after aperture correction is given by the "fluxaper" column. The 1 sigma error on the flux aperture measurment is given by the "erraper" column.
corrape float n/a Aperture correction factor. 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 flux 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. (Aug. 2008: See IMPORTANT NOTICE regarding flux)
idmain integer n/a ID of the counterpart in the Main (with respect to the Deep) catalog. Set to 0 if there are no counterparts.
distm float arcsec Distance in arcsec to the counterpart (offset between the position measured for the Deep catalog source and the position of the source judged to be its counterpart in the Main catalog). A maximum matching distance of 2.4 arcsec was used for counterparts. Anything with a larger matching distance is considered without ID in the other catalog, and the matching distance is set to 99.99 (has no counterparts).