Pulsar viewing geometry, expressed by the angles α and ζ, obtained by a fit to the gamma-ray data with the TPC model (panel a) and with the OG model (panel b). Pulsars on the dashed diagonal line (α = ζ) beam their radio emission to Earth regardless of their beam opening angle. Radio emission from pulsars between the two colored dashed lines is only detectable if their respective beam width ρ ≤ 16.8°, whereas pulsars between the two dash-dotted lines are visible if ρ ≤ 22.5°. Pulsars detected in radio are shown with large filled circles; pulsars without detected radio emission are shown with small empty circles.