Quantifying errorbeam contributions to the observed ¹³CO(1–0) emission. (Left) The map presents the percentage errorbeam contribution to individual sightlines for the 30m only data. We only consider sightlines where the integrated ¹³CO(1–0) brightness temperature is detected at ≳3σ. Contours indicate the S/N at 5,10,20, and 50. The red contour illustrates the SWAN FoV. Overall, the error beam contribution is marginal, with elevated values up to 10% within the interarm region (and < 5% within the SWAN FoV). (Right) We extract ¹³CO(1–0) spectra in six individual apertures. Apertures 1–4 are in the interarm region and apertures 5–6 in the spiral arms of M51. Each panel shows the full spectrum which includes the contribution from the error beam in blue. The brown spectrum represents the error beam contribution and was calculated by subtracting the error beam free spectrum from the observed spectrum. The percentage contribution is computed over the spectral range where we detect emission (indicated by the blue-shaded region) and is listed in each panel.