Volume 604, August 2017
|Number of page(s)||8|
|Section||Galactic structure, stellar clusters and populations|
|Published online||27 July 2017|
A tale of three cities
OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster
1 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
2 INAF–Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy
3 Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, 35122 Padova, Italy
4 Science Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
5 European Southern Observatory, Alonso de Córdova 3107, 19001 Casilla Santiago, Chile
6 School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane Campus, Hatfield, AL10 9AB, UK
7 Departamento de Astronomía, Universidad de Chile, Casilla 36-D Correo Central, Santiago, Chile
8 CSIC-INTA Centro de Astrobiologia Carretera Ajalvir km 4, 28550 Madrid, Spain
9 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
10 Armagh Observatory, College Hill, Armagh BT61 9DG, UK
11 Astrophysics Group, Keele University, Keele ST5 5BG, UK
12 Excellence Cluster Universe, Garching bei München, Germany
Received: 13 January 2017
Accepted: 26 May 2017
As part of the accretion discs in Hα with OmegaCAM (ADHOC) survey, we imaged a region of 12 × 8 square degrees around the Orion Nebula Cluster in r, i and Hα. 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.
Key words: stars: pre-main sequence / open clusters and associations: individual: Orion
© ESO, 2017
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.