Astrophys. J., 744, 163 (2012/January-2)
A search for interstellar carbon-chain alcohol HC4 OH in star-forming region L1527 and dark cloud TMC-1.
ARAKI M., TAKANO S., YAMABE H., KOSHIKAWA N., TSUKIYAMA K., NAKANE A., OKABAYASHI T., KUNIMATSU A. and KUZE N.
Abstract (from CDS):
We report a sensitive search for the rotational transitions of the carbon-chain alcohol HC4 OH in the frequency range 21.2-46.7 GHz in the star-forming region L1527 and the dark cloud TMC-1. The motivation was laboratory detection of HC4 OH by microwave spectroscopy. Despite achieving rms noise levels of several millikelvin in the antenna temperature using the 45 m telescope at Nobeyama Radio Observatory, the detection was not successful, leading to 3σ upper limits corresponding to the column densities of 2.0x1012 and 5.6x1012/cm2 in L1527 and TMC-1, respectively. These upper limits indicate that [HC4OH]/[HC5N] ratios are less than 0.3 and 0.1 in L1527 and TMC-1, respectively, where HC5 N is an HC4-chain cyanide and HC4OH is a hydroxide. These ratios suggest that the cyano carbon-chain molecule dominates the hydroxyl carbon-chain molecule in L1527 and TMC-1. This is contrary to the case of saturated compounds in hot cores, e.g., CH3 OH and CH3CN, and can be a chemical feature of carbon-chain molecules in L1527 and TMC-1. In addition, the column densities of the "unsubstituted" carbon-chain molecule C4 H and the sulfur-bearing molecules SO and HCS+ were determined from detected lines in L1527.
astrochemistry - ISM: clouds - ISM: molecules - radio lines: ISM
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