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

## TL;DR

This study provides the first observational estimate of the gas inflow rate into the Milky Way's Central Molecular Zone, revealing episodic variability likely linked to galactic dynamics.

## Contribution

It introduces a simple geometrical model to determine the inflow rate from CO data, demonstrating episodic accretion in the Galactic center.

## Key findings

- Total inflow rate is approximately 2.7 solar masses per year.
- Inflow rate varies over time, indicating episodic accretion.
- Both dust lanes contribute significantly to the inflow.

## Abstract

It is well known that the Galactic bar drives a gas inflow into the Central Molecular Zone, which fuels star formation, accretion onto the central super-massive 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 $^{12}$CO 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 $1.2^{+0.7}_{-0.8}\, \rm M_\odot yr^{-1}$ and along the far-side dust lane is $1.5^{+0.9}_{-1.0}\, \rm M_\odot yr^{-1}$, which gives a total inflow of $2.7^{+1.5}_{-1.7}\, \rm M_\odot yr^{-1}$. We also provide the time series of the inflow rate $\dot{M}$ for the future few Myr. The latter shows that the inflow rate is variable with time, supporting a scenario of episodic accretion onto the Central Molecular Zone.