Ambipolar-diffusion timescale, star formation timescale, and the ages of molecular clouds: Is there a discrepancy?

We reexamine critically the estimates of the duration of different phases of star formation and the lifetimes of molecular clouds based on the ages of T Tauri stars, age spreads of stars in clusters, and statistics of prestellar cores. We show that all available observational data are consistent with lifetimes of molecular clouds comparable to approximate to10(7) yr, as well as with the predictions of the theory of self-initiated, ambipolar-diffusion-controlled star formation. We conclude that there exists no observational support for either young'' molecular clouds or rapid'' star formation.