Members of 5 cluster in Ori OB1a association

DOI

The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13Myr old. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with 10% precision. While four of the clusters have ages between 11 and 13Myr, the ASCC 20 cluster stands out at an age of 21+/-3Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21Myr old population on the younger parts of the complex, including their formation.

Cone search capability for table J/A+A/631/A166/table1 (Parameters used in the final step of the clustering algorithm)

Cone search capability for table J/A+A/631/A166/tableb1 (Members of ASCC 16)

Cone search capability for table J/A+A/631/A166/tableb2 (Members of ASCC 21)

Cone search capability for table J/A+A/631/A166/tableb3 (Members of ASCC 21a)

Cone search capability for table J/A+A/631/A166/tableb4 (Members of ASCC 20)

Cone search capability for table J/A+A/631/A166/tableb5 (Members of ASCC 18)

Identifier
DOI http://doi.org/10.26093/cds/vizier.36310166
Source https://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/A+A/631/A166
Related Identifier https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/631/A166
Related Identifier http://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/631/A166
Metadata Access http://dc.g-vo.org/rr/q/pmh/pubreg.xml?verb=GetRecord&metadataPrefix=oai_b2find&identifier=ivo://CDS.VizieR/J/A+A/631/A166
Provenance
Creator Kos J.; Bland-Hawthorn J.; Asplund M.; Buder S.; Lewis G.F.; Lin J.,Martell S.L.; Ness M.K.; Sharma S.; De Silva G.M.; Simpson J.D.,Zucker D.B.; Zwitter T.; Cotar K.; Spina L.
Publisher CDS
Publication Year 2019
Rights https://cds.unistra.fr/vizier-org/licences_vizier.html
OpenAccess true
Contact CDS support team <cds-question(at)unistra.fr>
Representation
Resource Type Dataset; AstroObjects
Discipline Astrophysics and Astronomy; Exoplanet Astronomy; Galactic and extragalactic Astronomy; Natural Sciences; Observational Astronomy; Physics; Stellar Astronomy