On the Origin of Infrared Bands Attributed to Tryptophan in Spitzer Observations of IC 348

• Published in: Astrophysical journal. Letters Vol. 968; no. 1; p. L9
• Main Authors: Dhariwal, Aditya, Speak, Thomas H., Zeng, Linshan, Rashidi, Amirhossein, Moore, Brendan, Berné, Olivier, Remijan, Anthony J., Schroetter, Ilane, McGuire, Brett A., Rivilla, Víctor M., Belloche, Arnaud, Jørgensen, Jes K., Djuricanin, Pavle, Momose, Takamasa, Cooke, Ilsa R.
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01-06-2024; IOP Publishing
• Subjects: Amino acids; Astrochemistry; Infrared emissions; Infrared spectra; Interstellar gas; Interstellar medium; Interstellar molecules; James Webb Space Telescope; Laboratory astrophysics; Star clusters; Tryptophan; Vapor phases
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ad4d9a

Abstract Infrared emission features toward interstellar gas of the IC 348 star cluster in Perseus have been recently proposed to originate from the amino acid tryptophan. The assignment was based on laboratory infrared spectra of tryptophan pressed into pellets, a method which is known to cause large frequency shifts compared to the gas phase. We assess the validity of the assignment based on the original Spitzer data as well as new data from JWST. In addition, we report new spectra of tryptophan condensed in para-hydrogen matrices to compare with the observed spectra. The JWST MIRI data do not show evidence for tryptophan, despite deeper integration toward IC 348. In addition, we show that several of the lines attributed to tryptophan are likely due to instrumental artifacts. This, combined with the new laboratory data, allows us to conclude that there is no compelling evidence for the tryptophan assignment.