Mass inflow rate into the Central Molecular Zone: observational determination and evidence of episodic accretion

It is well known that the Galactic bar drives a gas inflow into the Central Molecular Zone, which fuels star formation, accretion on to the central supermassive black hole, and large-scale outflows. This inflow happens mostly through two symmetrical dust lanes, similar to those often seen in external barred galaxies. Here, we use the fact that the Milky Way dust lanes have been previously identified in (CO)-C-12 datacubes and a simple geometrical model to derive the first observational determination of the mass inflow rate into the Central Molecular Zone. We find that the time-averaged inflow rate along the near-side dust lane is 1.2(-0.) (+0.7)(8) M-circle dot yr(-1) and along the far-side dust lane is 1.5(-1.0)(+0.9) M-circle dot yr(-1), which gives a total inflow of 2.7(-1.7)(+1.5) M-circle dot yr(-1). We also provide the time series of the inflow rate M for the future few Myr. The latter shows that the inflow rate is variable with time, supporting a scenario of episodic accretion on to the Central Molecular Zone.