Fig. 3: Projection of the star-forming plane along the H_I direction.

a Distribution of star formation rate (SFR) and molecular gas mass (\({M}_{{{\rm{H}}}_{2}}\)) in the representative xGASS/xCOLD GASS sample for galaxies with M_star = 10^10±0.3M_⊙ (blue dots with 1−σ uncertainty contours) and isocontours of the probability density of galaxies with the same stellar mass range according to the fiducial model (dashed lines include 68 and 95% of galaxies in the continuous component). Solid lines show the corresponding contours for a mock sample based on the fiducial model with observational errors and detection limits added. Observational data with missing SFRs (molecular gas masses) are shown as magenta (green) circles at the bottom (left) edge of (a). Censored observational data are omitted for clarity of presentation. The red star indicates the peak position of the star-forming sequence and the molecular gas sequence for galaxies with M_star = 10¹⁰M_⊙ according to the fiducial model. b, c Marginal probability density functions (pdf) of the xGASS/xCOLD GASS sample (blue histograms), the mock sample (yellow histograms), and the fiducial model (dashed curves) for M_star = 10^{10 ± 0.3}M_⊙ galaxies. d Number of M_star = 10^{10 ± 0.3}M_⊙ galaxies in the representative xGASS/xCOLD GASS sample with measured ('meas'), missing ('miss'), and undetected ('cen') SFR and/or \({M}_{{{\rm{H}}}_{2}}\) values. While the mock sample reproduces the observational data well, the differences between the mock data and the true model predictions suggest that significant biases can be introduced by censored, missing, and uncertain data.