Eigenvalues of the spiral arms (m = 1) for Model A. The real and imaginary parts of ω are both in units of . The six panels in the upper left corner are the eigenvalues for more massive disks (M_disk/M_• = 0.8), and the six panels in the lower right corner are those for less massive disks (M_disk/M_• = 0.2). The values of , M_disk/M_•, and R_out/R_in are marked on the top of each panel. The eigenvalue adopted in the present paper is marked in orange in each panel, and its value is also provided in the same panel.