Part 4: |
Section 4.5.3 Active Galaxy: NGC 3031/Messier 81:
NGC 3031 or Messier 81 is an Sb(r)I-II galaxy at 1.4 Mpc. It has been an important galaxy in the study of star formation and density wave theory. It has an inclination of 58°.
Optical and HI observations (Yun, Ho and Lo 1994) of NGC 3031/M 81 and NGC 3034/M 82 (the dominant members of the M 81 Group) are shown in Figure 4.120.
NGC 3031/M 81 is given a secondary classification of I.
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Kendall et al. (2008) derive the density wave structure via residual mass maps using
Spitzer, optical and 2MASS data. The offset between the density wave and gas shocks
(seen via 8 µm dust emission) implies a long-lived spiral structure.
Gordon et al. (2004) investigate star formation and dust content using Spitzer,
UV, H and 20 cm continuum images. HI
observations (Yun, Ho and Lo 1994) of NGC 3031/M 81 and NGC 3034/M 82
(the dominant members of the M 81 Group) (Figure 4.120)
show dramatic evidence of tidal interactions (filaments)
between group members that is not seen in the optical.