Spitzer Documentation & Tools
IRS Instrument Handbook



6.6.5             Example IRS Data 


Figure 6.3:  Flat field images for the Short-Low (left) and Long-Low (right) modules. These images illustrate the full areas of the detector arrays dedicated to each spectral order.  For both modules, the 1st order (longer wavelength) spectrum is on the left and the 2nd order (shorter wavelength) spectrum is on the right; wavelength increases from top to bottom within each order.  The short bonus segment is visible above the 2nd order spectrum for both modules.  The SL image also shows the two peak-up arrays.  Spectral fringing is visible in the LL1 spectrum.


Figure 6.4:  Unprocessed point-source data from the SL (left) and LL (right) modules.  The SL image shows a spectrum obtained in 2nd order (along with the 1st order bonus segment at the top and the saturated IRS peak-up arrays on the right), while the LL image shows a spectrum obtained in 1st order.

Figure 6.5:  Example bcd.fits image of a galactic nucleus.  In this case the galaxy was observed using the 1st order Short-Low sub-slit (SL1).  The bright continuum can be seen running vertically down the image on the left.  Two bright (and several faint) emission lines/bands are clearly detected as features of increased intensity superimposed on the continuum.  The square regions to the right are the well-exposed peak-up apertures.  Note that light from the 2nd order SL sub-slit (SL2) is also deposited on the detector array to the right of SL1; however, SL2 is off-target (i.e., SL2 is looking at blank sky).  This is because the SL2 sub-slit is located more than 1 arcminute away from the SL1 target position on the Spitzer focal plane.  Consequently, there is no apparent SL2 spectrum.


Figure 6.6:  Example bcd.fits and coa2d.fits IRS data products for a bright (~0.5 Jy at 15 microns) galaxy with strong emission lines observed using the Short-High (SH) module of the IRS.  The rest frame 12.81 micron [NeII] line, appearing at an observed wavelength of ~13.1 microns, is circled in both images.  Due to the overlap between orders in SH, the [NeII] emission line appears in both orders 15 and 16 in these data. The bcd.fits and coa2d.fits files are from the first nod position.  Six individual nod frames were combined to produce the coa2d.fits image.

Figure 6.7:  Unprocessed point-source data from the SH and LH modules. Both images show the typical layout of a cross-dispersed echellogram. 


Figure 6.8 Example image of a star in the red IRS peak-up array.  This image shows the onboard-processed DCE #3, with the rest of the image masked.

Figure 6.9:  In-orbit image of a point source on the blue IRS peak-up sub-array. The first diffraction ring of the point source is clearly visible.  Bright pixels in the image are cosmic ray hits.  The illuminated red peak-up sub-array is visible in the figure above the blue sub-array, but does not contain any stars.