Distributions of the Hα (color; Finkbeiner 2003) and 857 GHz dust (gray; Planck Collaboration I 2014) emission. The units of the Hα and 857 GHzmaps are R (Rayleigh, 4π × 10⁻⁴ photons cm⁻² s⁻¹ sr⁻¹) and MJy str⁻¹, respectively.The magenta dashed circle indicates a HI supershell (Lim et al. 2013). The diameter of the HI supershell might be >200 pc since the distances to the Taurus and Perseus clouds are 140 and 340 pc, respectively. The distribution of HI emission is shown in Figs. A.4 and A.5. See also Fig. A.6.