Middle panel: [3.6] image of NGC 55, showing the area observed with GMOS. The image was recorded for the program described by Sheth et al. (2010), and was downloaded in processed form from the NASA Extragalactic Database. The image has been rotated so that the NGC 55 disk plane lies along the horizontal axis. North is toward the upper right corner, and east is toward the upper left corner. The green box has a length of 5 arcmin and a width of 0.4 arcmin, and shows the area covered by the disk pointings. The vertical green line marks the slit location for the minor axis pointing. Upper and lower panels: mean [3.6] light profiles of the regions that have positive and negative offsets from the major axis. The differences between the two light profiles foreshadows the diversity of properties in the spectra. The light profile defined from positive offsets—where there is little or no contamination from the star-forming complexes H2 and H4—follows an exponential on each side of the minor axis. The negative offset light profile is less well defined and is not symmetric about the minor axis; aside from a bump to the left of the minor axis that is due to H2 and H4, the surface brightness near the the minor axis is a few tenths of a magnitude arcsec⁻² higher than that extrapolated from the disk light profile at larger positive radii.