GLIMPSEII v3.5 Image Delivery - January 2008 Background and Boundary matched 3.1 deg x 3.45 deg Mosaic images of l= 4.45 to 7.55 deg and l=352.45 to 355.55 deg, b= +-1.725 deg of the GLIMPSEII SURVEY region; 1.2" pixels This is SSC version S13.2 and later processing of the GLIMPSEII data taken in September 2005 (epoch 1; two visits on the sky) *and* April 2006 (epoch 2; one visit on the sky) *and* the re-observations of missing and bad frames. **The v3.5 processing may be removing real sky variations so we provide these **images IN ADDITION to the v2.0 images that do not have **the background matching. v3.0 - Background matched In the v3.0 1.2" pixel mosaic images, we match instrumental background variations between the ~5x5 arcmin IRAC BCD frames using the Montage mosaicing package (http://montage.ipac.caltech.edu/). Instrument artifacts (see the IRAC Data Handbook: http://ssc.spitzer.caltech.edu/irac/dh/) such as full array pull-up, first frame effect and frame pull-down are mostly removed from the images. We use the "level" option in the Montage mBgModel module (http://montage.ipac.caltech.edu/docs/mBgModel.html) to produce the background matched mosaics. See http://montage.ipac.caltech.edu/docs/algorithms.html#background for a discussion of the background modeling. This produces the v3.0 1.2" pixel background matched mosaics. v3.5 - Background and Boundary matched We further match across boundaries of the v3.0 1.2" pixel mosaics using the non- background matched v2.0 1.2" pixel mosaics as a guide. This helps to insure a more consistent background level across the v3.5 1.2" pixel mosaics. Here are the essential steps in producing the background_and_boundary corrected images. The 1.2" pixel mosaics overlap by 320 pixels. 1) Create a difference image of bkg_corrected (v3.0) to non-bkg_corrected (v2.0) images. 2a) For each row in the difference image determine the median of first 320 pixels. b) Fit a 2nd order polynomial curve to these median values. 3a) Determine median of last 320 pixels of each row. b) Fit a 2nd order polynomial curve to those median values. 4) Initialize a correction image. The values of the first column of that image is the polynomial curve determined in step 2b. The values of the last column of the correction image is the polynomial curve determined in step 3b. 5) For each row in the correction image interpolate a linear correction from the value in the first column to the value in the last column. 6) This is the correction image. Subtracting the correction image from the (v3.0) bkg_corrected image produces the new improved (v3.5) background_and_boundary corrected image. Each mosaic fits file is about 386 MBytes. jpeg files are around 700 KBytes per file. Each mosaic fits file has an associated .hdr file which contains the fits header from the fits file and additional information about the individual frames included in the mosaic image. For example, the associated .hdr file for GLM_00600+0000_mosaic_I1.fits is GLM_00600+0000_mosaic_I1.hdr. ============================================================================================ (ch 1,2,4) mosaic fits file associated jpg file longitudes covered ----------------------------- --------------------------- ------------------- GLM_00600+0000_mosaic_I1.fits GLM_00600+0000_3.1x3.45.jpg 4.45 to 7.55 deg GLM_00600+0000_mosaic_I2.fits GLM_00600+0000_mosaic_I3.fits GLM_00600+0000_mosaic_I4.fits GLM_35400+0000_mosaic_I1.fits GLM_35400+0000_3.1x3.45.jpg 352.45 to 355.55 deg GLM_35400+0000_mosaic_I2.fits GLM_35400+0000_mosaic_I3.fits GLM_35400+0000_mosaic_I4.fits