2012ApJ...758L...4S

The millimeter-wave rotational transition line (J_K= 1₀-0₀) of deuterated methane CH₃ 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 CH₃ D in interstellar clouds, if confirmed. The column density and fractional abundance of CH₃ D are determined to be (9.1±3.4)x10¹⁵/cm2 and (3.0±1.1)x10^–7, respectively, where we assume the rotational temperature of 25 K. The column density and fractional abundance of the gaseous CH₄ are estimated to be (1.3-4.6) x 10¹⁷/cm2 and (4.3-15.2)x10^–6, respectively, by adopting the molecular D/H ratios of 2%-7% reported for various molecules in L1527. The fractional abundance of CH₄ is higher than or comparable to that found in high-mass star-forming cores by infrared observations. It is sufficiently high to trigger the efficient production of various carbon-chain molecules in a lukewarm region near the protostar, which supports the scenario of warm carbon-chain chemistry.