Multiple bursts of star formation in young star clusters: The case of the Orion Nebula Cluster

TL;DR

This paper presents evidence that the Orion Nebula Cluster experienced multiple star formation bursts, challenging the traditional single-burst model, supported by new observations and a theoretical model involving feedback and dynamics.

Contribution

It provides new observational data and a theoretical framework explaining multiple star formation episodes in the ONC.

Findings

The ONC has three distinct age-separated stellar populations.

Star formation in the ONC is ongoing and occurred in multiple bursts.

A model involving feedback and cluster dynamics explains the observed populations.

Abstract

Young star clusters (YSCs) with resolved stellar populations are well suited for studying star-cluster formation. In most cases, the (pre-main-sequence) stellar populations found in the YSCs are coeval with an intrinsic age spread of up to 1Myr. Such observations can be understood as the YSCs having formed in one burst, which star formation was truncated by stellar feedback. The recent discovery that the colour-magnitude diagram of the Orion Nebula Clusters (ONC) contains three well defined age-separated populations appears to shatter this model. The implication is that the ONC formed in three bursts, with star formation still on-going in the last burst. We present new observational results focusing on the three populations in the ONC using OmegaCAM photometry and Gaia DR2 measurements. We also describe a theoretical model which may explain these observations by an interplay between stellar feedback and cluster dynamics.