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

TL;DR

This study reports the tentative first detection of deuterated methane (CH$_3$D) in an interstellar cloud, specifically toward a low-mass protostar, providing insights into molecular abundances and chemical processes in star-forming regions.

Contribution

It presents the first tentative detection of CH$_3$D in an interstellar cloud and estimates its abundance, supporting theories of warm carbon-chain chemistry near protostars.

Findings

Tentative detection of CH$_3$D toward IRAS 04368+2557

Estimated column density and abundance of CH$_3$D

High abundance of CH$_4$ supports warm carbon-chain chemistry

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 $(9.1\pm3.4) \times 10^{15}$ cm$^{-2}$ and $(3.0\pm1.1) \times 10^{-7}$, 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.