Full width at half maximum (FWHM) of the Hα line from SDSS DR8 vs. FWHM of CO from ALLSMOG and xCOLDGASS. The dotted red line shows the velocity resolution equivalent of R = 2000 (FWHM ∼ 150 km/s), which is typical for SDSS DR8 at this redshift. The dashed gray line shows the one-to-one relation. Galaxies targeted with high-resolution spectroscopy are marked with green diamonds. Targets without detections in CO are marked with vertical line markers on the x-axis at the position corresponding to their SDSS-inferred Hα line widths. The dashed black and white line shows the running median in logarithmic bins of 0.2 dex width. The solid blue line shows a linear fit to the data with resolved Hα lines (i.e., to the right of the R = 2000 line), which is extrapolated into the unresolved regime as a dashed line. The color scaling corresponds to the stellar mass of the galaxies.