# The vertical metallicity gradients of mono-age stellar populations in the Milky Way with the RAVE and Gaia data

## TL;DR

This study analyzes how the vertical metallicity gradients of mono-age stellar populations in the Milky Way vary with age, revealing a trend of increasing gradient steepness and metallicity dispersion with age, supporting a flaring disc formation scenario.

## Contribution

It provides the first detailed analysis of vertical metallicity gradients across multiple mono-age populations using combined RAVE and Gaia data.

## Key findings

- No vertical metallicity gradient in the youngest stars.
- Steeper negative gradients in older populations.
- Metallicity dispersion increases with age.

## Abstract

We investigate the vertical metallicity gradients of five mono-age stellar populations between 0 and 11 Gyr for a sample of 18 435 dwarf stars selected from the cross-matched Tycho-Gaia Astrometric Solution (TGAS) and RAdial Velocity Experiment (RAVE) Data Release 5. We find a correlation between the vertical metallicity gradients and age, with no vertical metallicity gradient in the youngest population and an increasingly steeper negative vertical metallicity gradient for the older stellar populations. The metallicity at disc plane remains almost constant between 2 and 8 Gyr, and it becomes significantly lower for the $8 < \tau \leqslant 11$ Gyr population. The current analysis also reveals that the intrinsic dispersion in metallicity increases steadily with age. We discuss that our results are consistent with a scenario that (thin) disc stars formed from a flaring (thin) star-forming disc.