Unveiling hidden properties of young star clusters: differential reddening, star-formation spread and binary fraction

TL;DR

This paper introduces a semi-analytical method using adaptive simulated annealing to accurately determine key parameters of young star clusters from photometric data, even with complicating factors like differential reddening and binaries.

Contribution

The paper presents a novel semi-analytical approach combined with ASA to retrieve multiple cluster parameters from Hess diagrams, accounting for realistic effects like reddening and binaries.

Findings

Successfully retrieves cluster parameters from simulated data.

Effectively accounts for differential reddening and binaries.

Provides a comprehensive tool for young cluster analysis.

Abstract

Usually, important parameters of young, low-mass star clusters are very difficult to obtain by means of photometry, especially when differential reddening and/or binaries occur in large amounts. We present a semi-analytical approach that, applied to the Hess diagram of a young star cluster, is able to retrieve the values of mass, age, star-formation spread, distance modulus, foreground and differential reddening, and binary fraction. The global optimisation method known as adaptive simulated annealing (ASA) is used to minimise the residuals between the observed and simulated Hess diagrams of a star cluster. The simulations are realistic and take the most relevant parameters of young clusters into account. Important features of the simulations are: a normal (Gaussian) differential reddening distribution, a time-decreasing star-formation rate, the unresolved binaries, and the smearing effect produced by photometric uncertainties on Hess diagrams. Free parameters are: cluster mass, age, distance modulus, star-formation spread, foreground and differential reddening, and binary fraction.