Revisiting the selection and the impact on the detection rate. Predicted I₂₁ fluxes with the original L_IR based on PACS detections and on the new IR photometry from Jin et al. (2018). The symbols mark the whole parent sample of 123 galaxies with ALMA Band 6 observations targeting CO (5 − 4). Gray crosses, gray open circles, and blue open circles indicate sources with uncertain and reliable information on CO (5 − 4) (Flag <  0,  0,   ≥ 0.5, respectively, Sect. 3.2.2). Red filled circles show galaxies with reliable information on CO (2 − 1) (Flag ≥ 0.5). Open red circles mark objects with predicted fluxes bright enough to be observed according to both the initial and the revised SED modeling, but that did not enter the final selection due to the frequency grouping. The black solid lines indicate the depth of the ALMA Band 3 observations: objects on the right side of the vertical line were selected for the follow-up (excluding the red open circles); object above the horizontal line could have been selected, if the updated photometry were available when preparing the observations. Objects with missing photometry in Jin et al. (2018) are artificially set to I_CO(2−1) = 0.15 Jy km s⁻¹ and labeled accordingly.