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Table 4
Arm parameters for the best-fitted PL spiral arm models (see Eq. (5)).
| ith arm | a i | b i | c i | d i | θ start | θ end |
| (°) | (°) | |||||
|
|
||||||
| HII regions, R0 = 8.5 kpc, Θ0 = 220 km s-1, Z = 0.16. | ||||||
| arm-1 | 1.1923 | 0.1499 | –0.007056 | 0.0 | 40 | 250 |
| arm-2 | 7.4144 | –2.4119 | 0.3105 | –0.01223 | 275 | 620 |
| arm-3 | 6.8191 | –2.1630 | 0.2888 | –0.01163 | 275 | 570 |
| arm-4 | 2.6019 | –0.3315 | 0.03829 | 0.0 | 275 | 500 |
| arm-5 | 1.7840 | –0.04095 | 0.01956 | 0.0 | 280 | 475 |
| arm-6 | 3.1816 | –0.5408 | 0.07024 | 0.0 | 280 | 355 |
| Ri (kpc) | θi (°) | 
(°) |
||||
| Local Arm | 8.64 | 52.0 | 1.00 | |||
|
|
||||||
| All three kinds of spiral tracers, Z = 0.18. | ||||||
| arm-1 | 1.2170 | 0.1442 | –0.007552 | 0.0 | 40 | 250 |
| arm-2 | 7.4413 | –2.4138 | 0.3103 | –0.01222 | 275 | 620 |
| arm-3 | 6.8185 | –2.1632 | 0.2887 | –0.01162 | 280 | 625 |
| arm-4 | 1.8419 | –0.09367 | 0.02001 | 0.0 | 280 | 500 |
| arm-5 | 1.7020 | –0.01485 | 0.01522 | 0.0 | 280 | 500 |
| arm-6 | 2.0497 | –0.05168 | 0.01807 | 0.0 | 280 | 405 |
| Ri (kpc) | θi (°) |
(°) |
||||
| Local Arm | 8.60 | 51.9 | 0.76 | |||
|
|
||||||
| HII regions, R0 = 8.3 kpc, Θ0 = 239 km s-1, Z = 0.16. | ||||||
| arm-1 | 1.1668 | 0.1198 | 0.002557 | 0.0 | 40 | 250 |
| arm-2 | 5.8002 | –1.8188 | 0.2352 | –0.008999 | 275 | 620 |
| arm-3 | 4.2300 | –1.1505 | 0.1561 | –0.005898 | 275 | 570 |
| arm-4 | 0.9744 | 0.1405 | 0.003995 | 0.0 | 280 | 500 |
| arm-5 | 0.9887 | 0.1714 | 0.004358 | 0.0 | 280 | 475 |
| arm-6 | 3.3846 | –0.6554 | 0.08170 | 0.0 | 280 | 355 |
| Ri (kpc) | θi (°) |
(°) |
||||
| Local Arm | 8.10 | 52.2 | 2.36 | |||
|
|
||||||
| All three kinds of spiral tracers, Z = 0.17. | ||||||
| arm-1 | 1.1320 | 0.1233 | 0.003488 | 0.0 | 40 | 250 |
| arm-2 | 5.8243 | –1.8196 | 0.2350 | –0.009011 | 275 | 620 |
| arm-3 | 4.2767 | –1.1507 | 0.1570 | –0.006078 | 275 | 575 |
| arm-4 | 1.1280 | 0.1282 | 0.002617 | 0.0 | 280 | 500 |
| arm-5 | 1.7978 | –0.04738 | 0.01684 | 0.0 | 280 | 500 |
| arm-6 | 2.4225 | –0.1636 | 0.02494 | 0.0 | 280 | 405 |
| Ri (kpc) | θi (°) |
(°) |
||||
| Local Arm | 8.17 | 57.8 | 2.84 | |||
Notes. The fitting is made to HII regions and all three kinds of spiral tracers, respectively.
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