Hunting for Runaways from the Orion Nebula Cluster

Abstract

We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45° around the ONC and out to 1 kpc to find sources that overlapped in angular position with the cluster in the last ~10 Myr. We find ~17,000 runaway/walkaway candidates satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and WISE photometry; (3) having a high degree of optical variability; (4) having closest approach distances well constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC and discuss its implications for cluster formation theories via comparison with numerical simulations.

22 pages, 10 figures, and 5 tables. Accepted for publication in ApJ

References in corpus (12)

• The Gaia mission
• Equilibrium Star Cluster Formation
• A Classification Scheme for Young Stellar Objects Using the WIDE-FIELD INFRARED SURVEY EXPLORER AllWISE Catalog: Revealing Low-Density Star Formation in the Outer Galaxy
• Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O
• Identification of Young Stellar Object candidates in the $Gaia$ DR2 x AllWISE catalogue with machine learning methods
• A Tale of Three Cities: OmegaCAM discovers multiple sequences in the color-magnitude diagram of the Orion Nebula Cluster
• The Structure, Dynamics and Star Formation Rate of the Orion Nebula Cluster
• Runaway and walkaway stars from the ONC with Gaia DR2
• When the tale comes true: multiple populations and wide binaries in the Orion Nebula Cluster
• The Orion Protostellar Explosion and Runaway Stars Revisited: Stellar Masses, Disk Retention, and an Outflow from BN
• Dynamical evolution of star-forming regions: III. Unbound stars and predictions for Gaia
• A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars

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• From downtown to the outskirts: a radio survey of the Orion Nebula Cluster
• Finding the dispersing siblings of young open clusters. Dynamical traceback simulations using Gaia DR3
• Analysis of Selected Runaway Stars in the Orion Nebula Based on Data from the Gaia EDR3 Catalogue
• Deviations from the universal Initial Mass Function in binary star clusters