Left: Stacked CO(1–0) image-plane for 19 sources with robust CO(1–0) detections. For the image-plane stack, the contours are drawn at ±(2, 4, 6…)σ, where 1σ = 0.014 Jy km s⁻¹), and the white ellipses indicate the mean FWHM beam size (4.24″ × 2.73″, PA = 1.7 deg). Right: Visibility-plane stack. The uv-plane data are integrated over ±1 FWHM velocity range and radially binned with a step of 5 kλ. For CO(1–0), the exponential model with R_1/2 = 0.49 ± 0.07″ (3.8 ± 0.5 kpc at our median redshift z = 3.1) is strongly preferred by the available data.