An Upper Limit to the Age of the Galactic Bar

Abstract

Using data from the Two Micron All Sky Survey, we identify a population of infrared carbon stars with J-K_S ≥ 2 in the Milky Way. These stars are shown to trace the stellar bar previously identified in IR and optical surveys. The properties of C stars strongly suggest that they are of intermediate age. We conclude that the bar is likely to have formed more recently than 3 Gyr ago and must be younger than 6 Gyr. Implications and further tests of this conclusion are briefly discussed.