Far-Infrared Distributions in Nearby Spiral Galaxies NGC 2841 and NGC 2976 Observed with AKARI/Far-Infrared Surveyor (FIS)

Abstract

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 µm 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 (∼ 21 K) ring for NGC 2841 and a warm (∼ 30 K) ring for NGC 2976, which presumably reflects the difference in the origin of the ring structure for the different Hubble type of the galaxy. In addition to the dust ring structure, a warm dust component is detected from the central region of NGC 2841, which may be attributed to the heating by its Low-Ionization Nuclear Emission-line Region nucleus. As for NGC 2976, an extended dust component is observed along the minor axis, which shows a distribution somewhat asymmetrical to the galactic disk; this might be associated with the HI bridge in the M81/M82 group that NGC 2976 belongs to. By taking advantage of a wealth of the far-IR bands of the FIS, it is demonstrated that the spectral energy distribution of NGC 2841 is spatially more variable than that of NGC 2976.

On filaments, prolate halos and rotation curves

“…Alternatively, such an object could be a tidal stream: for instance, another key example NGC 5907 is known to host an extended stellar tidal stream structure [33,34]. One more prominent example, NGC 2841, has a polar ring orthogonal to the galaxy plane, which is probably a result of interaction with another galaxy [35,36]. In addition, one could conjecture that the "strings" at the centers of galaxies are connected to the large-scale intergalactic filaments.…”