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| Paper: |
Pattern speeds from integration of the continuity equation - The speed and origin of the spiral pattern in M81 |
| Volume: |
18, The Interpretation of Modern Synthesis Observations of Spiral Galaxies |
| Page: |
175 |
| Authors: |
Westpfahl, David |
| Abstract: |
By integration of the continuity equation the pattern speed of a disk galaxy may be related to the velocity field and surface brightness of a well-defined class of pattern tracers. Application to the nearby spiral M81 gives an average pattern speed of 24 km/s kpc, but the pattern is shearing at the rate -2 km/s sq kpc. This is consistent with the pattern being caused by Toomre's swing amplifier due to a close passage of M82 and NGC 3077 about 5 x 10 exp 8 years ago. |
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