CO(4–3) spectrum of the CO emission in the brightest pixel of the central source in SW022550 (left panel) and SW022513 (right panel). The LSR velocity scale is relative to z = 3.866 for SW022550, and z = 3.427 for SW022513. The lines represent the best-fits obtained with a single Gaussian (red solid line), and with a double Gaussian (each component is shown with a dotted blue line and the sum with a solid blue line). The green dashed line represents a single Gaussian fit with FWHM equal to the best-fit value obtained for the other source, i.e., FWHM=800kms^-1 in SW022513 and FWHM=1020kms^-1 in SW022550. The best-fit parameters are listed in Table 1 and the reduced-χ² are annotated on the upper left corner. The residuals obtained from the single and the double Gaussian component fits are shown in the bottom panels with a solid red and blue line, respectively.