The nearby face-on spiral galaxy M101 has been observed with the Far-Infrared Surveyor ( FIS ) onboard AKARI .
The far-infrared four-band images reveal fine spatial structures of M101 , which include global spiral patterns , giant H \emissiontype II regions embedded in outer spiral arms , and a bar-like feature crossing the center .
The spectral energy distribution of the whole galaxy shows the presence of the cold dust component ( 18 ^ { +4 } _ { -10 } K ) in addition to the warm dust component ( 55 ^ { +9 } _ { -25 } K ) .
The distribution of the cold dust is mostly concentrated near the center , and exhibits smoothly distributed over the entire extent of the galaxy , whereas the distribution of the warm dust indicates some correlation with the spiral arms , and has spotty structures such as four distinctive bright spots in the outer disk in addition to a bar-like feature near the center tracing the CO intensity map .
The star-formation activity of the giant H \emissiontype II regions that spatially correspond to the former bright spots is found to be significantly higher than that of the rest of the galaxy .
The latter warm dust distribution implies that there are significant star-formation activities in the entire bar filled with molecular clouds .
Unlike our Galaxy , M101 is a peculiar normal galaxy with extraordinary active star-forming regions .