A New Surface Density Model of Jovian Trojans around Triangular Libration Points

We constructed a new surface number density distribution model for Jovian Trojans around the L4 or L5 libration point of Jupiter. This is an empirical asymmetric model of the Maxwellian-Gaussian type, derived from numerical integrations of orbital motions for actual Trojan asteroids around the L4 point. With this model, in combination with the observed surface number densities obtained by Yoshida and Nakamura (2005, AJ, 130, 2900; 2008, PASJ, 60, 297), we estimate that the total populations of L4 and L5 Trojans with diameters (D)>2km are (6.3±1.0)×10⁴ and (3.4±0.5) ×10⁴, respectively. These results indicate that the L4 total populations (D> 2km) calculated previously by Jewitt, Trujillo, and Luu (2000, AJ, 120, 1140) and by Yoshida and Nakamura (2005, ibid.) using the former's isotropic Gaussian model are overestimated by a factor of 3-4.