CO moment 0 maps of NGC 4501 and NGC 4402. Left panels: resulting from clipping the CO data cube at a constant level of 75 mK. Right panels: after the procedure described in Sect. 2.1 involving the Hi data cubes.

NGC 4254: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32,64,128)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64,128) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) 10 Myr. Middle right: star formation rate  as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4321: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32,64,128)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64,128) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64,128) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4330: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4330: top left: star formation rate based on Hα and TIR emission in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16)  5 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4402: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  8 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64,128) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4419: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  5 × 10^-3 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64,128) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Diamonds are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The dashed line indicates the level at which we had to clip the star formation rate due to PSF effects of the bright nucleus. The arrow takes into account the CO detection limit.

NGC 4438: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  4.5 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64,128) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The dashed line indicates the level at which we had to clip the star formation rate due to PSF effects of the bright nucleus. The arrow takes into account the CO detection limit.

NGC 4438: top left: star formation rate based on Hα and TIR emission in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  15 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4501: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32,64)  5 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64,128) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4522: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4522: top left: star formation rate based on Hα and TIR emission in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32)  6 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4548: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4569: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32,64)  8 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4579: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32,64) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70) × 10 Myr. Middle right: star formation rate as a function of the molecular gas surface density Σ_H2. Diamonds are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.

NGC 4654: top left: star formation rate (from UV+TIR) in contours on a greyscale map of the total gas surface density. Contour levels are (1,2,4,8,16,32,64,128)  3 × 10^-4 M_⊙ kpc^-2 pc^-1. Greyscale levels are (1,2,4,8,16,32,64) M_⊙ pc^-2. Top right: total gas surface density contours on the molecular gas fraction Σ_H2/Σ_HI. Greyscale levels are (1,2,4,8,16,32) × 0.1. Middle left: total gas surface density contours on the star formation timescale . Greyscale levels are (1,10,20,30,40,50,60,70,80,90,100) × 10 Myr. Middle right: star formation rate  as a function of the molecular gas surface density Σ_H2. The vertical set of points at the lowest Σ_mol are upper limits for Σ_mol. Lower left: star formation rate as a function of the atomic gas surface density Σ_HI. Lower right: star formation rate as a function of the total gas surface density Σ_g = Σ_H2 + Σ_HI. The solid line corresponds to a star formation timescale of t_∗ = 2 Gyr. The arrow takes into account the CO detection limit.