A tale of three cities - OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster

Wright, Nicholas J.

Abstract

As part of the accretion discs in Ha with OmegaCAM (ADHOC) survey, we imaged a region of 12 × 8 square degrees around the Orion Nebula Cluster in r, i and Ha. Thanks to the high-quality photometry obtained, we discovered three well-separated pre-main sequences in the color-magnitude diagram. The populations are all concentrated towards the cluster’s center. Although several explanations can be invoked to explain these sequences, we are left with two competitive but intriguing scenarios: a population of unresolved binaries with an exotic mass ratio distribution, or three populations with different ages. Independent high-resolution spectroscopy supports the presence of discrete episodes of star formation, each separated by about a million years. The stars from the two putative youngest populations rotate faster than the older ones, in agreement with the evolution of stellar rotation observed in pre-main sequence stars younger than 4 Myr in several star forming regions.? Whatever the final explanation, our results prompt a revised look at the formation mode and early evolution of stars in clusters.

Citation

Wright, N. J. (2017). A tale of three cities - OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster. Astronomy and Astrophysics, A22 - A22. https://doi.org/10.1051/0004-6361/201730432

• Acceptance Date: May 26, 2017
• Publication Date: Jul 27, 2017
• Journal: Astronomy and Astrophysics
• Print ISSN: 2329-1273
• Publisher: Hans Publishers
• Pages: A22 - A22
• DOI: https://doi.org/10.1051/0004-6361/201730432
• Keywords: stars: pre-main sequence, open clusters and associations: individual: Orion
• Publisher URL: https://doi.org/10.1051/0004-6361/201730432