Far-infrared distributions in nearby spiral galaxies NGC 2841 and NGC 2976 observed with AKARI/Far-Infrared Surveyor (FIS)

Far-infrared (IR) images of the nearby Sb galaxy NGC 2841 and the Sc galaxy NGC 2976 at wavelengths of 65, 90, 140, and 160 mu m have been obtained with the Far-Infrared Surveyor (FIS) onboard AKARI. Both galaxies reveal similar morphologies of dust rings. They are, however, significantly different in the dust temperature: a cold (similar to 21 K) ring for NGC 2841 and a warm (similar to 30 K) ring for NGC 2976, which presumably reflects the difference in the origin of the ring structure for the different Hubble types of the galaxy. In addition to the dust-ring structure, a warm dust component was detected from the central region of NGC 2841, which may be attributed to heating by its Low-Ionization Nuclear Emission-line Region nucleus. As for NGC 2976, an extended dust component was observed along the minor axis, which shows a distribution somewhat asymmetrical to the galactic disk; this might be associated with the H I bridge in the M 81/M 82 group that NGC 2976 belongs to. By taking advantage of a wealth of the far-IR bands of the FIS, it has been demonstrated that the spectral energy distribution of NGC 2841 is spatially more variable than that of NGC 2976.