Table 2.
Comparison of rotation in regions of M 51, showing the results for both samples.
| Property | S/N = 7 | S/N = 10 | Comments |
|---|---|---|---|
| Whole Galaxy | |||
| Prograde | 435 | 257 | |
| Retrograde | 247 | 119 | |
| Regions of Fig. 6 | |||
 |
0.0084 | 0.0080 | Ave cloud grad km s−1 pc−1 |
 |
−0.0035 | −0.0052 | Ave cloud grad km s−1 pc−1 |
 |
−0.0096 | −0.0137 | Ave cloud grad km s−1 pc−1 |
 |
−0.0217 | −0.0252 | Ave cloud grad km s−1 pc−1 |
| Effect of spiral arms | |||
| Arm | 143 | 66 | Retrograde |
| Arm | 201 | 116 | Prograde |
| Not arm | 104 | 53 | Retrograde |
| Not arm | 234 | 141 | Prograde |
| Effect of location within spiral arms | |||
| Leading | 98 | 42 | Retrograde |
| Leading | 69 | 37 | Prograde |
| Inner | 45 | 24 | Retrograde |
| Inner | 132 | 79 | Prograde |
| Not arm | 104 | 53 | Retrograde |
| Not arm | 234 | 141 | Prograde |
Notes. Top part shows that rotation is generally prograde. The second part shows that cloud rotation follows galactic shear. The third part shows that the fraction of retrograde rotators is higher in the spiral arms. The last part shows that the retrograde rotators are mostly found in and actually dominate the leading edge of the arms. The fraction of pro- and retrograde rotators does not vary between the red and blue shifted parts of the “not arm” regions.
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