Orion Source I's disk is salty

Abstract

We report the detection of NaCl, KCl, and their ${}^{37}$Cl and ${}^{41}$K isotopologues toward the disk around Orion SrcI. About 60 transitions of these molecules were identified. This is the first detection of these molecules in the interstellar medium not associated with the ejecta of evolved stars. It is also the first ever detection of the vibrationally excited states of these lines in the ISM above v = 1, with firm detections up to v = 6. The salt emission traces the region just above the continuum disk, possibly forming the base of the outflow. The emission from the vibrationally excited transitions is inconsistent with a single temperature, implying the lines are not in LTE. We examine several possible explanations of the observed high excitation lines, concluding that the vibrational states are most likely to be radiatively excited via rovibrational transitions in the 25-35 μm (NaCl) and 35-45 μm (KCl) range. We suggest that the molecules are produced by destruction of dust particles. Because these molecules are so rare, they are potentially unique tools for identifying high-mass protostellar disks and measuring the radiation environment around accreting young stars.

Accepted to ApJ. Analysis code at https://github.com/keflavich/Orion_ALMA_2016.1.00165.S, paper source at https://github.com/keflavich/SaltyDisk, and data at https://zenodo.org/record/1213350

References in corpus (6)

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• Disk-Driven Rotating Bipolar Outflow in Orion Source I
• The ALMA View of the OMC1 Explosion in Orion
• ALMA Observations of Orion Source I at 350 and 660 GHz
• New Evidence for the Dynamical Decay of a Multiple System in the Orion Kleinmann-Low Nebula
• The circumestellar disk of the B0 protostar powering the HH 80-81 radio jet