12 and 20 micron imaging of the starburst galaxy NGC 253

We present 12 and 20 micron imaging of the starburst galaxy NGC 253 with a spatial resolution of 0.8" (10 pc at an assumed distance to NGC 253 of 2.5 Mpc). Using previous groundbased mid-IR studies to determine the absolute position of our images, we estimate a positional uncertainty in our images of 1.6". We conclude that the proposed "nucleus" of NGC 253, i.e., the dominant, bright, flat-spectrum radio source identified by Turner & Ho (TH 2), is not associated with the mid- infrared peak, but rather is located 2.2" (27 Pc) to the northeast. We place the mid-infrared peak IRS 1, midway between TH 6 and TH 7. With this positioning we find several coincidences with our 12 micron image: IRS 1 falls within 1" of the 2 micron peak; a second significantly weaker infrared source, IRS 2, coincides with TH 2; the brightest steep-spectrum 6 cm radio source, TH 9, coincides with a "tongue" of emission extending to the southwest of IRS 1; and the only flat-spectrum source of the six identified by Antonucci & Ulvestad that does not lie on the major axis of the radio emission coincides with a "tongue" of emission extending to the southeast of IRS 2. The integrated flux in our images accounts for approximately half of the measured IRAS flux. IRS 1 and 2 account for approximately 50% of our total image flux. The 12-20 micron color temperature is remarkably uniform across the entire nuclear region with a mean value of 138 K and standard deviation of 8 K, in good agreement with the IRAS 12-25 micron color temperature of 147 K. However, there is some indication of spatial structure in the color temperature, with the coolest temperatures along the main ridge of emission and progressively warmer temperatures away from the ridge.