MWISP ¹³CO (1–0) velocity-integrated intensity image of Tycho’s SNR. The unit of the scale bar is K km s^-1. The emission is integrated between −65 and −59 km s^-1, and the contours start at 3σ and then increase in steps of 2σ (1σ ~ 0.4 K km s^-1). The red circle shows the position and size of the shell-like structure in Tycho’s SNR, while the yellow dashed ellipse shows the cavity found in the MWISP ¹²CO images. The numbers in the image mark the positions for sampling the CO spectra of the clouds.