# Constraining churning and blurring in the Milky Way using large spectroscopic surveys -- an exploratory study

## TL;DR

This study explores how stars in the Milky Way move due to processes like blurring and churning, using large spectroscopic surveys combined with Gaia data to quantify their impact on stellar migration.

## Contribution

It introduces a framework to distinguish and quantify the effects of churning and blurring in stellar migration using elemental abundances, ages, and orbital data.

## Key findings

- Approximately 50% of stars experienced radial migration.
- About 10% have undergone only churning.
- 5-7% of stars show no evidence of either process.

## Abstract

We have investigated the possibilities to quantify how much stars move in the Milky Way stellar disk due to diffuse processes (i.e. so called blurring) and due to influences from spiral arms and the bar (i.e. so called churning). To this end we assume that it is possible to infer the formation radius of a star if we know their elemental abundances and age as well as the metallicity profile of the interstellar medium at the time of the formation of the star. Using this information, coupled with orbital information derived from Gaia DR2 data and radial velocities from large spectroscopic surveys, we show that it is possible to isolate stellar samples such that we can start to quantify how important the role of churning is. We use data from APOGEE DR14, parallaxes from Gaia and stellar ages based on C and N elemental abundances in the stars. In our sample, we find that about half of the stars have experienced some sort of radial migration (based solely on their orbital properties), 10 % have likely have suffered only from churning, whilst a modest 5-7 % of stars have never experienced either churning or blurring making them ideal tracers of the original properties of the cool stellar disk. Our investigation shows that it is possible to put up a framework where we can begin to quantify churning and blurring an important. Important aspects for future work would include to investigate how selection effects should be accounted for.