Spectroscopic redshift offset between submillimeter and optical or near-IR observations. Bottom: the blue filled circles indicate the new z_{spec, submm} determinations for trustable emission lines detected by ALMA against the optical or near-IR z_spec, opt from the COSMOS master compilation (Salvato et al., in prep.). The solid black line marks the locus of z_{spec, submm} = z_spec, opt. Top: v_submm − v_opt difference as a function of z_spec, opt, excluding three catastrophic strong outliers and an ascertained misidentification. The solid and dotted lines mark the mean and the 1σ dispersion of the sample.