Evidence for dense gas heated by the explosion in Orion KL

Abstract

We mapped the kinetic temperature structure of Orion KL in a $\sim$20${}^{\prime \prime }$ ($\sim$8000 AU) sized region with para-H${}_2$CS $7_{07}-6_{06}$, $7_{26}-6_{25}$, and $7_{25}-6_{24}$ making use of ALMA Band 6 Science Verification data. The kinetic temperatures obtained with a resolution of $1\hbox{$\,.\!\!^{\prime\prime}$}65$$\times$$1\hbox{$\,.\!\!^{\prime\prime}$}14$ ($\sim$550 AU) are deduced by modeling the measured averaged velocity-integrated intensity ratios of para-H${}_2$CS $7_{26}-6_{25}/7_{07}-6_{06}$ and $7_{25}-6_{24}/7_{07}-6_{06}$ with a RADEX non-LTE model. The kinetic temperatures of the dense gas, derived from the para-H${}_2$CS line ratios at a spatial density of 10${}^7$ cm${}^{-3}$, are high, ranging from 43 to $>$500 K with an unweighted average of $\sim$170 K. There is no evidence for internal sources playing an important role in the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump, and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecular filaments traced by H${}_2$CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive event, which occurred several hundred years ago greatly affecting the energetics of the Orion KL region. Thus, with the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL are probably caused by shocks from the explosive event, leading to a dominant component of externally heated dense gas.

Accepted for publication to ApJ

References in corpus (21)

• The distance to the Orion Nebula
• The Gould's Belt Distances Survey (GOBELINS) II. Distances and structure towards the Orion Molecular Clouds
• Monitoring the Large Proper Motions of Radio Sources in the Orion BN/KL Region
• The ALMA View of the OMC1 Explosion in Orion
• VLA observations of ammonia in high-mass star formation regions
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde
• The Orion Protostellar Explosion and Runaway Stars Revisited: Stellar Masses, Disk Retention, and an Outflow from BN
• Temperature structures in Galactic Center clouds - Direct evidence for gas heating via turbulence
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde. II. The Large Magellanic Cloud
• The Proper Motions of the Double Radio Source n in the Orion BN/KL Region
• New Evidence for the Dynamical Decay of a Multiple System in the Orion Kleinmann-Low Nebula
• Temperature profiles of young disk-like structures: The case of IRAS 16293A
• ALMA Imaging of Millimeter/Submillimeter Continuum Emission in Orion KL
• VERA and ALMA Observations of the H2O Supermaser Burst in Orion KL
• A Detailed View of the Circumstellar Environment and Disk of the Forming O-star AFGL 4176
• Sulfur-bearing molecules in Orion KL
• ALMA observations of the archetypal "hot core" that isn't: Orion KL
• The complexity of Orion: an ALMA view III. The explosion impact
• Physical and chemical differentiation of the luminous star-forming region W49A - Results from the JCMT Spectral Legacy Survey
• NH${}_3$ (1,1) hyperfine intensity anomalies in the Orion A molecular cloud

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• The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
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• Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I. Orion A
• Mapping physical parameters in Orion KL at high spatial resolution
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde V. The massive filament DR21
• On the Relationship between CH${}_3$OD Abundance and Temperature in the Orion KL Nebula
• A Tale of Three: Magnetic Fields along the Orion Integral-Shaped Filament as Revealed by JCMT BISTRO survey
• Unmasking the physical information inherent to interstellar spectral line profiles with Machine Learning. I. Application of LTE to HCN and HNC transitions