First Image with the CfA Superconductive HEB Receiver: The Protostellar Outflow from IRAS 20126+4104 in CO (J = 7–6)

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Abstract
We present a spectral line image in CO (J = 7–6) of the spatially compact molecular outflow from the massive protostar IRAS 20126+4014, observed using a novel superconductive hot‐electron bolometer (HEB) heterodyne receiver we recently installed at the 10 m Heinrich Hertz Telescope. The bipolar outflow is clearly detected and resolved with a center of symmetry situated at the position of the massive protostar, previously identified as an IRAS source and a millimeter continuum source. The peaks of the emission from the red‐ and blueshifted CO lobes are separated by ≈14'' (0.1 pc), and the velocity of the CO emission extends ±30 km s−1 from the ambient cloud velocity. The total outflowing gas mass is approximately 4M⊙, while the outflow rate is at least 6 × 10-4 M⊙ yr−1. Both high‐velocity CO emission maxima trail the NH3 (3, 3) and SiO clumps located 3''–4'' downstream (farther from the IR source) in the flow. The high‐excitation CO line and the NH3 are likely tracing the heated gas entrained in different parts of the bow shocks. By interpreting our observations in terms of a jet‐driven model, we estimate the density in the underlying jet to be at least 105 cm−3. The outflow appears much more compact and in a different orientation than the arcminute‐scale north/south flow seen in low‐J transitions of CO. These observations represent the first successful operation of a superconductive HEB receiver on a telescope and demonstrate the importance of high‐frequency submillimeter lines to the understanding of the protostellar environment.