Herschel/PACS Spectroscopic Survey of Protostars in Orion: The Origin of Far-Infrared CO Emission

Understand

We present far-IR (57-196 mu) spectra of 21 protostars in the Orion molecular clouds, obtained with the Photodetector Array Camera and Spectrometer (PACS) onboard the Herschel Space observatory, as part of the Herschel Orion Protostar Survey (HOPS) program.

• We analyzed the CO emission lines (J_up = 14-46) in the PACS spectra, extracted within a projected distance of <= 2000 AU centered on the protostar.
• The total luminosity of the CO lines observed with PACS (L(CO)) is found to increase with increasing L_bol.
• The CO rotational temperature implied by the line ratios increases with J, and at least 3-4 rotational temperature components are required to fit the observed rotational diagram.