Near-infrared color properties of Kuiper Belt objects and Centaurs: Final results from the ESO large program

We present near-IR JHK broadband photometry for 17 Kuiper Belt objects (KBOs) and Centaurs. The observations were performed within the ESO Large Program on the "Physical Properties of Kuiper Belt Objects and Centaurs'' from 2001 January to 2002 August. We used the ISAAC instrument at the ESO 8 m Very Large Telescope. We compiled visible-near-IR colors for a total of 51 published objects and performed a statistical analysis. Color-color correlations show that the same coloring process is probably acting on Centaur and KBO surfaces in the visible near-IR range. Centaurs with H-K smaller than the Sun (0.06) systematically display the reddest B-V colors (at the 2.5 sigma level). These Centaur surfaces are suspected of harboring material that has spectral signatures around 1.7-2.2 mu m (water ice is a possibility; it was reported for the three objects that have published spectroscopy). We report no statistically significant evidence for a bimodal structure of the VJHK Centaur colors (Kolmogorov-Smirnov and dip tests on up to 17 objects). The Centaur H-K colors show some robust evidence (significance level > 99.99%) for a continuous structure. We also report a statistically significant bimodal structure of the Centaur B-R distribution, which is compatible with the results published by Peixinho et al. in 2003 with different data. Classical KBOs show no trends at the 3 sigma level. The V-J color is marginally correlated with perihelion distance q (which is consistent with results reported by Doressoundiram et al. in 2005 on B-R colors). Resonant and scattered disk objects are under-represented ( seven and nine objects, respectively) and show no statistically significant trend. Some of the marginal trends are mentioned as worthy of subsequent monitoring.