Tentative Detection of Deuterated Methane toward the Low-Mass Protostar IRAS 04368+2557 in L1527

Abstract

The millimeter-wave rotational transition line ($J_K=1_0-0_0$) of deuterated methane CH${}_3$D has tentatively been detected toward the low-mass Class 0 protostar IRAS 04368+2557 in L1527 with the Heinrich Hertz Submillimeter Telescope. This is the first detection of CH${}_3$D in interstellar clouds, if confirmed. The column density and fractional abundance of CH${}_3$D are determined to be $(9.1\pm 3.4)\times 10^{15}$ cm${}^{-2}$ and $(3.0\pm 1.1)\times 10^{-7}$, respectively, where we assume the rotational temperature of 25 K. The column density and fractional abundance of the gaseous CH${}_4$ are estimated to be $(1.3-4.6)\times 10^{17}$ cm${}^{-2}$ and $(4.3-15.2)\times 10^{-6}$, respectively, by adopting the molecular D/H ratios of 2--7% reported for various molecules in L1527. The fractional abundance of CH${}_4$ is higher than or comparable to that found in high-mass star-forming cores by infrared observations. It is sufficiently high for triggering the efficient production of various carbon-chain molecules in a lukewarm region near the protostar, which supports the picture of the warm carbon-chain chemistry.

13 pages

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