2026ApJ...996L..32L

We present the first spatially resolved map of methanimine (CH₂NH) 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 CH₂NH emission across the core. The peak line intensity coincides with the well-known c-C₃H₂ peak, while the integrated intensity peaks between the HNCO and dust continuum peaks due to broader linewidths in the latter region. Column densities of CH₂NH are ∼(0.5-1.4×)10¹² 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 CH₂NH, 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.