Structural Parameters of Star Clusters: Stochastic Effects

TL;DR

This study investigates how stochastic effects of bright stars impact the accuracy of structural parameters in star clusters, highlighting the need for stochastic simulations to properly assess uncertainties.

Contribution

It introduces a simulation-based approach to quantify uncertainties in cluster structural parameters caused by stochastic stellar effects.

Findings

Clusters under $10^4 M_\odot$ show large uncertainties in size parameters.

Young clusters (<10 Myr) have systematically underestimated sizes.

Stochastic simulations are essential for accurate structural parameter estimation.

Abstract

Stochasticity of bright stars introduces uncertainty and bias into derived structural parameters of star clusters. We have simulated a grid of cluster $V$-band images, observed with Subaru Suprime-Cam with age, mass, and size representing a cluster population in the M31 galaxy and derived their structural parameters by fitting King model to the surface brightness distribution. We have found that clusters less massive than $10^4 M_\odot$ show significant uncertainty in their core and tidal radii for all ages, while clusters younger than 10 Myr have their sizes systematically underestimated for all masses. This emphasizes the importance of stochastic simulations to asses the true uncertainty of structural parameters in studies of semi-resolved and unresolved clusters.