# The EDGE-CALIFA survey: Variations in the Molecular Gas Depletion Time in Local Galaxies

## TL;DR

This study uses spatially resolved CO and optical data to analyze how molecular gas depletion time varies within local galaxies, revealing central regions often have shorter depletion times linked to stellar density.

## Contribution

It provides the first detailed spatial analysis of molecular gas depletion time variations within local galaxies using combined EDGE and CALIFA data.

## Key findings

- 14 galaxies show shorter central depletion times (~1 Gyr) compared to disks (~2.4 Gyrs)
- Central regions with shorter depletion times have higher stellar surface density
- Shorter depletion times are linked to molecular gas compression by stellar gravity

## Abstract

We present results from the EDGE survey, a spatially resolved CO(1-0) follow-up to CALIFA, an optical Integral Field Unit (IFU) survey of local galaxies. By combining the data products of EDGE and CALIFA, we study the variation in molecular gas depletion time ($\tau_{\rm dep}$) on kiloparsec scales in 52 galaxies. We divide each galaxy into two parts: the center, defined as the region within $0.1 \ R_{25}$, and the disk, defined as the region between $0.1$ and $0.7 \ R_{25}$. We find that 14 galaxies show a shorter $\tau_{\rm dep}$ ($\sim 1$ Gyr) in the center relative to that in the disk ($\tau_{\rm dep} \sim 2.4$ Gyrs), which means the central region in those galaxies is more efficient at forming stars per unit molecular gas mass. This finding implies that the centers with shorter $\tau_{\rm dep}$ resemble the intermediate regime between galactic disks and starburst galaxies. Furthermore, the central drop in $\tau_{\rm dep}$ is correlated with a central increase in the stellar surface density, suggesting that a shorter $\tau_{\rm dep}$ is associated with molecular gas compression by the stellar gravitational potential. We argue that varying the CO-to-H$_2$ conversion factor only exaggerates the central drop of $\tau_{\rm dep}$.