First Mapping of Prebiotic Molecule CH ₂ NH in a Prestellar Core

Abstract We present the first spatially resolved map of methanimine (CH 2 NH) in the prestellar core L1544 using the IRAM 30 m telescope. The 2 0,2 –1 0,1 line at 127 GHz was mapped with 20″ resolution (∼2800 au), revealing extended CH 2 NH emission across the core. The peak line intensity coincides with the well-known c-C 3 H 2 peak, while the integrated intensity peaks between the HNCO and dust continuum peaks due to broader linewidths in the latter region. Column densities of CH 2 NH are ∼(0.5–1.4×)10 12 cm −2 , corresponding to fractional abundances of 5 × 10 −11 –1 × 10 −10 , with a trend decreasing from the southern, carbon-chain rich region to the dust and HNCO peak in the north. Comparison with complementary molecular maps and the gas-grain chemical model of Sipilä et al. suggests that neutral–neutral gas-phase reactions and dissociative recombination dominate in the outer carbon-chain shell. This study demonstrates that CH 2 NH, a simple nitrogen- and carbon-bearing molecule previously detected with pointed observations in other cold cores, is present and spatially extended in the evolved prestellar core L1544. This indicates that prebiotic nitrogen-carbon chemistry continues efficiently up to the onset of gravitational collapse, providing key constraints for astrochemical models and the early stages of chemical complexity leading to amino acids.