Tentative detection of deuterated methane toward the low-mass protostar iras 04368+2557 in L1527

The millimeter-wave rotational transition line (J_K = 1 ₀-0₀) of deuterated methane CH₃D 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 CH₃D in interstellar clouds, if confirmed. The column density and fractional abundance of CH₃D are determined to be (9.1 ± 3.4) × 10¹⁵cm^-2 and (3.0 ± 1.1) × 10^-7, respectively, where we assume the rotational temperature of 25K. The column density and fractional abundance of the gaseous CH₄ are estimated to be (1.3-4.6) × 10¹⁷cm ^-2 and (4.3-15.2) × 10^-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.