SHORT LIFETIME OF PROTOPLANETARY DISKS IN LOW-METALLICITY ENVIRONMENTS

We studied near-infrared disk fractions of six young clusters in the low-metallicity environments with [O/H] similar to -0.7 using deep JHK images with Subaru 8.2 m telescope. We found that disk fraction of the low-metallicity clusters declines rapidly in <1 Myr, which is much faster than the similar to 5-7 Myr observed for the solar-metallicity clusters, suggesting that disk lifetime shortens with decreasing metallicity possibly with an similar to 10(Z) dependence. Since the shorter disk lifetime reduces the time available for planet formation, this could be one of the major reasons for the strong planet-metallicity correlation. Although more quantitative observational and theoretical assessments are necessary, our results present the first direct observational evidence that can contribute to explaining the planet-metallicity correlation.