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

¹ Institut de Radioastronomie Millimétrique, 300 Rue de la Piscine, 38400 Saint-Martin-d’Hères, France
² Centro de Astrobiología (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, Madrid, Spain
³ INAF Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, 50125 Florence, Italy
⁴ Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching bei München, Germany
⁵ Laboratory for the study of the Universe and eXtreme phenomena (LUX), Observatoire de Paris, 5, place Jules Janssen, 92195 Meudon, France
⁶ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁷ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁸ Department of Space, Earth and Environment, Chalmers University of Technology, 412 96 Gothenburg, Sweden
⁹ Department of Astronomy, University of Virginia, 530 McCormick Road Charlottesville 22904-4325, USA
¹⁰ Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹¹ European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
¹² Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹³ Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 29 October 2025
Accepted: 8 December 2025

Abstract

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.