JOYS: Linking the molecular ice and gas phase composition toward the high-mass hot core IRAS 18089–1732

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
² Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
³ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁴ Max Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
⁶ INAF - Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
⁷ UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁸ Department of Physics, University of Helsinki, PO box 64, 00014 Helsinki, Finland
⁹ INAF - Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, Italy

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

Received: 17 December 2025
Accepted: 24 March 2026

Abstract

Context. The formation and destruction of molecules in the interstellar medium involve a complex interplay between gas phase reactions, as well as processes on grain surfaces and within icy mantles. In recent decades, the gas phase composition of the cold material toward star-forming regions could be well characterized using (sub)millimeter facilities. Prior to the launch of the James Webb Space Telescope (JWST), ice species other than the main constituents (i.e., H₂O, CO, CO₂, NH₃, CH₄, and CH₃OH) were challenging to detect due to insufficient sensitivity as well as angular and/or spectral resolution.

Aims. We aim to determine molecular ice and gas phase column densities toward the young and embedded high-mass hot core IRAS 18089-1732 within a region of 5000 au.

Methods. We used spectroscopic data from 5 to 28 μm obtained with JWST to derive the ice column densities of H₂O, SO₂, OCN⁻, CH₄, HCOO⁻, HCOOH, CH₃CHO, CH₃COOH, C₂H₅OH, CH₃OCH₃, and CH₃COCH₃. We inferred the gas phase column densities for a total of 38 molecules, including O-, N-, S-, and Si-bearing species, as well as less abundant isotopologs, from sensitive molecular line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at 3 mm wavelengths.

Results. We find comparable abundances (relative to C₂H₅OH or CH₃OH) in both phases for C₂H₅OH, CH₃OH, and CH₃OCH₃. The abundances of SO₂ and CH₃COCH₃ are higher in the gas phase, suggesting additional gas phase formation routes. The abundance of CH₃CHO is one order of magnitude higher in the ices compared to the gas phase. The ice abundances (relative to H₂O ice) toward the IRAS 18089 hot core are similar to previously studied Galactic low- and high-mass protostars. There are hints of a decreasing abundance with galactocentric distance for OCN⁻, CH₃OH, and CH₃CHO ices.

Conclusions. It is evident that not all species show comparable abundances in the ice and gas phases. However, we do find similar trends when species show elevated ice or gas phase abundances in the high-mass hot core IRAS 18089, compared to low-mass hot cores. To better understand the reaction pathways of molecular species, statistical surveys analyzing both the ice and gas phase chemical composition of high- and low-mass protostars at different Galactocentric radii are essential.