Year: 2026
Type: preprint
Abstract: The physical conditions of the interstellar medium (ISM) are thought to differ greatly at high redshifts compared to local galaxies. Polycyclic aromatic hydrocarbons (PAHs) are key ISM constituents, mediating the heating and cooling of gas in photo-dissociation regions. However, PAHs are unexplored in main-sequence (MS) galaxies at z~1-2 (cosmic noon), limiting our view of the ISM's thermal and chemical balance. We present the PAH Spectroscopic Survey (PAHSPECS) JWST program, the first MIRI/MRS survey of the 3.3, 6.2, 7.7, 8.6 and 11.3$μ$m PAH features in MS galaxies at z~1. The five targets come from the deep ALMA CO and continuum flux-limited sample in the HUDF. We detect the 6.2, 7.7 and 11.3$μ$m PAHs in all galaxies, and the 3.3$μ$m feature in only two. Spectral energy distribution (SED) fitting to broad-band mid-IR photometry recovers the 6.2 and 7.7$μ$m PAH luminosities derived from spectral decomposition of the MRS spectra to within ~25% accuracy. However, the 3.3 and 11.3$μ$m features are overestimated by ~50% (up to 3-5x). Spatially resolved maps of ASPECS-6, the most extended source, show variations of the 7.7$μ$m PAH contribution to the MIRI F1500W flux, suggesting that while photometry can infer PAH luminosity accurately, IFU spectroscopy is necessary to study variations in PAH ratios and characterize galaxy dust properties. The PAH fraction of the total dust mass from photometric SED modeling roughly agrees with the $L_{\rm PAH}/L_{\rm IR}$ ratio measured from spectroscopy, but the correlation is not as tight as models predict. On average, PAHSPECS galaxies show an excess in 6.2$μ$m equivalent width relative to nearby dusty luminous systems, but lower 3.3$μ$m equivalent widths than local systems, similar to higher-mass starbursts at z~1-3. This points to differential changes in the size distributions of neutral and ionized PAHs in cosmic noon galaxies.
Source: arXiv (Cornell University)
Authors: Shivaei, Irene, Santos, Tanio Díaz, Boogaard, Leindert A., Sandstrom, Karin, Lofaro, Cristina, Donnan, Fergus R., González, Pablo G. Pérez, Aránda, Roman Fernández, Márquez, Javier Álvarez, Aravena, Manuel, Decarli, Roberto, Galliano, Frédéric, Inami, Hanae, Östlin, Göran, Popping, Gergö, Walter, Fabian, van der Wer, Paul
Institutions: Centro de Astrobiología, FORTH Institute of Astrophysics, Foundation for Research and Technology Hellas, Leiden University, Leiden Observatory, University of California San Diego, Universidad Diego Portales, Osservatorio di Astrofisica e Scienza dello Spazio, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, Hiroshima University, Hiroshima Astrophysical Science Center, Stockholm University, AlbaNova, European Southern Observatory, Max Planck Institute for Astronomy
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Comunidad de Madrid, Space Telescope Science Institute, National Radio Astronomy Observatory, European Commission, Agence Nationale de la Recherche, Centre National d’Etudes Spatiales, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Korea Astronomy and Space Science Institute, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, Agencia Nacional de Investigación y Desarrollo, National Science and Technology Council, National Institutes of Natural Sciences, Institut National de Physique Nucléaire et de Physique des Particules
Awards: G103270039, G1424166960, G2421315707, G256731684, G433322167, G4518818167, MILLENIUM NUCLEUS FOR GALAXIES, G5084717281, G5568641063, G58316358, G6273510985, G6662351857, Revealing dust Evolution - Depletion, Emission and Extinction Modeling In Nearby Galaxies (REDEEMING), G7080048889, ORCHIDS: ORIGIN OF THE [CII] HALOS IN DISTANT SYSTEMS, CENTRO DE ASTROFISICA Y TECNOLOGIAS AFINES (CATA), Fuel Up: How Cold Gas Fuels Star Formation Through Cosmic Time
OpenAlex ID: W7214341229