Non-extensive processes associated with heating of the Galactic disc

TL;DR

This study applies non-extensive statistical mechanics to analyze the non-Gaussian velocity distributions in the Galactic disc, revealing non-random heating behavior especially in the vertical component, challenging previous assumptions.

Contribution

It introduces a non-extensive statistical model to Galactic disc heating analysis, highlighting non-random behavior in stellar velocity evolution, particularly in the vertical component.

Findings

Vertical velocity component W does not heat randomly.

The q-index varies non-randomly with stellar age.

Non-Gaussian effects are significant in galactic kinematic analysis.

Abstract

We analyse the mechanisms ruling galactic disc heating through the dynamics of space velocities $U$, $V$ and $W$, extracted from the Geneva-Copenhagen catalogue. To do this, we use a model based on non-extensive statistical mechanics, where we derive the probability distribution functions that quantify the non-Gaussian effects. Furthermore, we find that the deviation $q-1$ at a given stellar age follows non-random behaviour. As a result, the $q$-index behaviour indicates that the vertical component $W$, perpendicular to the Galactic plane, does not ``heat up'' at random, which is in disagreement with previous works that attributed the evolution of $W$ to randomness. Finally, our results bring a new perspective to this matter and open the way for studying Galactic kinematic components through the eyes of more robust statistical models that consider non-Gaussian effects.