Overdensity of CO emitters in the MQN01 field. Panel a: CO(4–3) LF in MQN01 and in blank fields. The (dark/light) red dots and boxes represent the CO LF in MQN01 field (fidelity (F) + completeness (C)-corrected/uncorrected, respectively) in ΔV₄₀₀₀, while gold hatched boxes are the uncorrected (raw) CO LF within ΔV₁₀₀₀. The blue and green boxes with black dots are data from ASPECS and HDF-N, respectively, which are representative of blank fields at these redshifts (e.g., Decarli et al. 2019, 2020; Boogaard et al. 2023). The downward arrows indicate 1σ upper limits. The dashed black line is the best-fit Schechter function to the ASPECS+HDF-N data reported in Boogaard et al. (2023). The orange line is the CO(4–3) LF prediction from SIDES simulation (Béthermin et al. 2022; Gkogkou et al. 2023) at z = 3 − 3.25. Gray lines represent the rescaled versions of such models. Panel b: Number of sources in each luminosity bin averaged over the iterations. The horizontal dashed line reports the total average number of sources entering each bin of the LFs. Panel c: Cumulative source number density as a function of the CO(4–3) line luminosity obtained by integrating the CO LFs. Panel d: Source overdensity in MQN01 field as a function of the CO(4–3) line luminosity obtained by a bin-to-bin ratio of the cumulative source number densities.