Larger-field FCRAO ¹²CO (1–0) intensity image around Tycho’s SNR, integrated between −68 and −57 km s^-1 (as same as Fig. 1). The contours start at 3σ and then increase in steps of 2σ (1σ ~ 1.7 K km s^-1). The red circle shows the shell-like structure in Tycho’s SNR, while the yellow ellipse shows the cavity found in the MWISP CO images. The green ellipses show similar cavity-like structures found in the FCRAO CO image.