A stochastic model to reproduce the star-formation history of individual galaxies in hydrodynamic simulations

TL;DR

This paper introduces a stochastic model that accurately reproduces the star formation histories of individual galaxies in hydrodynamical simulations by combining main sequence evolution with fractional Brownian motions.

Contribution

The model uniquely combines main sequence tracking with fractional Brownian motions to describe galaxy SFHs, providing a standard for simulation comparison.

Findings

Fractional Brownian motions can replicate many SFH features.

Main sequence evolution varies across simulations.

Variations and mass-loss rates are key for accurate SFH reconstruction.

Abstract

The star formation history (SFH) of galaxies is critical for understanding galaxy evolution. Hydrodynamical simulations enable us to precisely reconstruct the SFH of galaxies and establish a link to the underlying physical processes. In this work, we present a model to describe individual galaxies' SFHs from three simulations: TheThreeHundred, Illustris-1 and TNG100-1. This model divides the galaxy SFH into two distinct components: the "main sequence" and the "variation". The "main sequence" part is generated by tracing the history of the $SFR-M_*$ main sequence of galaxies across time. The "variation" part consists of the scatter around the main sequence, which is reproduced by fractional Brownian motions. We find that: 1) The evolution of the main sequence varies between simulations; 2) fractional Brownian motions can reproduce many features of SFHs, however, discrepancies still exist; 3) The variations and mass-loss rate are crucial for reconstructing the SFHs of the simulations. This model provides a fair description of the SFHs in simulations. On the other hand, by correlating the fractional Brownian motion model to simulation data, we provide a 'standard' against which to compare simulations.