A map of OMC-1 in CO 9-8

Abstract

The distribution of 12C16O J=9-8 (1.037 THz) emission has been mapped in OMC-1 at 35 points with 84" resolution. This is the first map of this source in this transition and only the second velocity-resolved ground-based observation of a line in the terahertz frequency band. There is emission present at all points in the map, a region roughly 4' by 6' in size, with peak antenna temperature dropping only near the edges. Away from the Orion KL outflow, the velocity structure suggests that most of the emission comes from the OMC-1 photon-dominated region, with a typical linewidthof 3-6 km/s. Large velocity gradient modeling of the emission in J=9-8 and six lower transitions suggests that the lines originate in regions with temperatures around 120 K and densities of at least 10^(3.5) cm^(-3) near theta^(1) C Ori and at the Orion Bar, and from 70 K gas at around 10^(4) cm^(-3) southeast and west of the bar. These observations are among the first made with the 0.8 m Smithsonian Astrophysical Observatory Receiver Lab Telescope, a new instrument designed to observe at frequencies above 1 THz from an extremely high and dry site in northern Chile.

Minor changes to references, text to match ApJ version

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• CO J=6--5 in Arp 220: strong effects of dust on high-J CO lines
• APEX CO (9-8) Mapping of an Extremely High-Velocity and Jet-like Outflow in a High-Mass Star-Forming Region
• A map of OMC-1 in CO 9-8
• Submillimeter Atmospheric Transparency at Maunakea, at the South Pole, and at Chajnantor
• Twenty years of PWV measurements in the Chajnantor Area
• Observations in the 1.3 and 1.5 THz Atmospheric Windows with the Receiver Lab Telescope
• High Velocity Outflow in CO J=7-6 from the Orion Hot Core
• First-generation Science Cases for Ground-based Terahertz Telescopes
• The sub-mm J=6-5 line of 13CO in Orion
• The distribution of warm gas in the G327.3--0.6 massive star-forming region