The population of faint Jupiter family comets near the Earth

We study the population of faint Jupiter family comets (JFCs) that approach the Earth (perihelion distances q < 1.3   AU ) by applying a debiasing technique to the observed sample. We found for the debiased cumulative luminosity function (CLF) of absolute total magnitudes H 10 a bimodal distribution in which brighter comets ( H 10 ≲ 9 ) follow a linear relation with a steep slope α = 0.65 ± 0.14 , while fainter comets follow a much shallower slope α = 0.25 ± 0.06 down to H 10 ∼ 18 . The slope can be pushed up to α = 0.35 ± 0.09 if a second break in the H 10 distribution to a much shallower slope is introduced at H 10 ∼ 16 . We estimate a population of about 103 faint JFCs with q < 1.3   AU and 10 < H 10 < 15 (radii ∼ 0.1 – 0.5   km ). The shallowness of the CLF for faint near-Earth JFCs may be explained either as: (i) the source population (the scattered disk) has an equally very shallow distribution in the considered size range, or (ii) the distribution is flattened by the disintegration of small objects before that they have a chance of being observed. The fact that the slope of the magnitude distribution of the faint active JFCs is very similar to that found for a sample of dormant JFCs candidates suggests that for a surviving (i.e., not disintegrated) object, the probability of becoming dormant versus keeping some activity is roughly size independent.