Bar-driven Transport of Molecular Gas in Spiral Galaxies: Observational Evidence

The NRO-OVRO CO imaging survey showed that molecular gas was more concentrated to the central kiloparsec in barred spiral galaxies than in their unbarred counterparts. The result provided not only evidence for bar-driven gas transport but also estimates on the mean rate of gas transfer and lower limits to the lifetime of bars. Other lines of evidence for the bar-driven transport of ISM in spiral galaxies are summarized. They are complementary with each other.