Free Access

Table 1

Arm parameters of the best-fitted models of logarithmic spirals (see Eq. (3)).

Models\Arm parameters R 1 θ 1 R 2 θ 2 R 3 θ 3 R 4 θ 4 R 5 θ 5 Z
(kpc) (°) (°) (kpc) (°) (°) (kpc) (°) (°) (kpc) (°) (°) (kpc) (°) (°)

Fitting of models to HII regions, R0 = 8.5 kpc, Θ0 = 220 km s-1.
3-arm model 3.42 44.4 8.85 3.72 192.3 9.29 3.01 219.4 8.62 8.61 51.3 0.50 0.17
4-arm model 3.40 44.9 11.70 4.41 190.1 10.82 3.58 217.6 10.68 3.60 320.9 11.06 8.64 50.4 0.99 0.16

Fitting of models to all three kinds of spiral tracers (HII regions, GMCs, and 6.7 GHz methanol masers).
3-arm model 3.40 45.8 9.12 3.78 194.7 9.29 3.47 230.4 7.61 8.59 54.7 0.62 0.20
4-arm model 3.23 41.2 10.64 4.27 189.0 11.15 3.56 217.9 10.63 3.81 309.8 8.85 8.64 53.8 0.59 0.17

Fitting of models to HII regions, R0 = 8.3 kpc, Θ0 = 239 km s-1.
3-arm model 3.19 36.8 9.00 3.27 191.9 10.36 3.13 230.7 8.16 8.20 51.1 2.63 0.16
4-arm model 3.35 44.4 11.43 4.61 192.4 9.84 3.56 218.6 10.38 3.67 330.3 10.54 8.21 55.1 2.77 0.16

Fitting of models to all three kinds of spiral tracers.
3-arm model 3.22 44.1 9.25 3.43 184.5 9.50 3.10 210.3 7.80 8.17 47.8 2.68 0.18
4-arm model 3.27 38.5 9.87 4.29 189.0 10.51 3.58 215.2 10.01 3.98 320.1 8.14 8.16 50.6 2.71 0.16

Notes. For the ith spiral arm, Ri is the initial radius, θi is the start azimuth angle, and is the pitch angle. The parameters of the Local Arm are denoted with subscript 5. The fitting factor Z (see Eq. (4)) for each model is shown in the last column.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.