Chemical complexity in star formation induced by stellar feedback: Cores shock-formed by the supernova remnant W44

Journal article, 2026

Context. Low-velocity shocks from supernova remnants (SNRs) may set the physical and chemical conditions of star formation in molecular clouds. Recent evidence suggests that even the Sun might have formed through this process. However, the chemical conditions of shock-induced star-forming regions remain poorly constrained. Aims. We study the chemical complexity of a shock-impacted clump, with the potential to yield star formation, named the Clump and located at the interface between the SNR W44 and the infrared dark cloud G034.77-00.55. We test whether the Clump has chemical properties consistent with those observed in star-forming regions unaffected by SNRs. Methods. We used high-sensitivity, broad spectral surveys at 3 and 7 mm obtained with the 30m antenna at the Instituto de Radioastronomia Millímetrica and the 40 m antenna at the Yebes observatory, to identify D-bearing molecules and complex organic molecules (COMs) towards the Clump. For all species, we estimated molecular abundances and compared them with those observed across starforming regions at different evolutionary stages and masses, as well as comets. Results. We detect multiple deuterated molecules (DCO⁺, DNC, DCN, CH2DOH) and COMs (CH3OH, CH3CHO, CH3CCH, CH3CN, CH3SH) with excitation temperatures of 5-13 K. To the best of our knowledge, this is the first detection of COMs towards a site of SNR-cloud interaction. The derived D/H ratios (~0.01-0.04) and COM abundances are consistent with those reported towards typical low-mass starless cores and comparable to cometary values. The overall level of chemical complexity is relatively low, in line with an early evolutionary stage. Conclusions. We suggest that the Clump is an early stage shock-induced low-mass star-forming region, not yet protostellar. We speculate that SNR-driven shocks may set the physical and chemical conditions to form stars. The resulting chemical budget may be preserved along the formation process of a planetary system, being finally incorporated into planetesimals and cometesimals.