The ALMA View of the OMC1 Explosion in Orion

Abstract

Most massive stars form in dense clusters where gravitational interactions with other stars may be common. The two nearest forming massive stars, the BN object and Source I, located behind the Orion Nebula, were ejected with velocities of $\sim$29 and $\sim$13 km s${}^{-1}$ about 500 years ago by such interactions. This event generated an explosion in the gas. New ALMA observations show in unprecedented detail, a roughly spherically symmetric distribution of over a hundred ${}^{12}$CO J=2$-$1 streamers with velocities extending from V${}_{LSR}$ =$-$150 to +145 km s${}^{-1}$. The streamer radial velocities increase (or decrease) linearly with projected distance from the explosion center, forming a `Hubble Flow' confined to within 50 arcseconds of the explosion center. They point toward the high proper-motion, shock-excited H${}_2$ and [Fe ii ] `fingertips' and lower-velocity CO in the H${}_2$ wakes comprising Orion's `fingers'. In some directions, the H${}_2$ `fingers' extend more than a factor of two farther from the ejection center than the CO streamers. Such deviations from spherical symmetry may be caused by ejecta running into dense gas or the dynamics of the N-body interaction that ejected the stars and produced the explosion. This $\sim$10${}^{48}$ erg event may have been powered by the release of gravitational potential energy associated with the formation of a compact binary or a protostellar merger. Orion may be the prototype for a new class of stellar explosion responsible for luminous infrared transients in nearby galaxies.

34 pages, 17 figures

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• An Asymmetric Keplerian Disk Surrounding the O-type Protostar IRAS16547$-$4247
• Orion Source I's disk is salty
• The Orion Protostellar Explosion and Runaway Stars Revisited: Stellar Masses, Disk Retention, and an Outflow from BN
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• The CARMA-NRO Orion Survey: Protostellar Outflows, Energetics, and Filamentary Alignment
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• The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
• The complexity of Orion: an ALMA view III. The explosion impact
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• Supersonic Expansion of the Bipolar Hii Region Sh2-106: A 3,500 Year-Old Explosion?
• G5.89: An Explosive Outflow Powered by a Proto-Stellar Merger?
• Observations of Orion Source I Disk and Outflow Interface
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• Magnetic Field Structure of Orion Source I
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• Magnetic fields and outflows in the large Bok globule CB 54
• Possible Explosive Dispersal Outflow in IRAS 16076-5134 revealed with ALMA
• The CARMA-NRO Orion Survey: Statistical Signatures of Feedback in the Orion A Molecular Cloud
• Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions
• Hierarchical Structure of YSO Clusters in the W40 and Serpens South Region: Group Extraction and Comparison with Fractal Clusters
• Confirming the Explosive Dispersal Outflow in DR21 with ALMA
• Studying star-forming processes at core and clump scales: the case of the young stellar object G29.862-0.0044
• An orbital release model for the Orion BN/KL fingers
• A molecular-line study of the interstellar bullet engine IRAS 05506+2414
• VVV-WIT-01: highly obscured classical nova or protostellar collision?
• Formation of Orion Fingers
• Modelling the CO streamers in the explosive ejection of Orion BN/KL region
• Explosive ejections generated by gravitational interactions