Confidence levels of evolutionary synthesis models

TL;DR

This paper investigates the inherent uncertainties in evolutionary synthesis models of stellar clusters, focusing on confidence limits of parameters like EW(Hb), and quantifies the dispersion of these parameters due to stochastic IMF effects.

Contribution

It introduces a method to quantify confidence limits in synthesis models, accounting for stochastic IMF variations in young stellar clusters.

Findings

Dispersion of EW(Hb) is about 18% at 90% confidence for 10^5 Mo clusters.

Confidence levels provide a measure of uncertainty in model predictions.

Stochastic effects significantly impact the interpretation of observed cluster parameters.

Abstract

The stochastic nature of the IMF in young stellar clusters implies that clusters of the same mass and age do not present the same unique values of their observed parameters. Instead they follow a distribution. We address the study of such distributions, parameterised in terms of their confidence limits, in evolutionary synthesis models. These confidence limits can be understood as the inherent uncertainties of the synthesis models. Here we concentrate on some parameters such as EW(Hb) in emission. For instance, we show that for a cluster where 10^5 Mo have been transformed into stars, the dispersion of EW(Hb) is about 18% within the 90% confidence levels at ages between 3.5 and 5 Myrs.