Color-coded stellar mass density distribution in the disk R–ϕ plane for the vertical slice of ﹩| Z| \lt 0.2\,\mathrm{kpc}﹩. Different panels are results for different age bins, as marked in the lower left corner. For each bin, density values shown in the figure are time-averaged by dividing the age span of the bin. The plus sign indicates the position of the Sun, while the inner and outer ovals delineate, respectively, a constant distance of 0.2 and 1.0 kpc from the Sun on the disk midplane. Triangles are sources of molecular masers associated with the Local arm from Xu et al. (2013).