Year: 2026
Type: preprint
Abstract: Context. Cosmic noon (z ~ 1-3) marks the peak of the cosmic star-formation rate density, when dust-obscured star formation dominated galaxy growth. Mid-infrared spectroscopy probes the interstellar medium through PAH emission, whose band ratios trace PAH charge, size, and local radiation-field conditions. Aims. We characterize the PAH properties of five z ~ 1.1 star-forming galaxies from the PAHSPECS survey and investigate how their PAH luminosities and band ratios relate to global galaxy properties. We compare them with local luminous infrared galaxies (LIRGs) to assess whether PAH emission at cosmic noon differs from that nearby. Methods. We analyze JWST/MIRI MRS observations of five ASPECS galaxies in the HUDF. Integrated spectra are extracted with wavelength-dependent apertures and modeled with CAFE, including ancillary photometry to constrain the dust emission. Stellar masses and SFRs are derived with Prospector. Results. Compared to local LIRGs, most PAHSPECS sources show higher 6.2/7.7 and lower 11.3/7.7 ratios, suggesting an ionized PAH component weighted toward smaller grains. The 3.3/11.3 ratio is less constrained, since the 3.3 micron feature is detected in only two sources. Within the sample, 11.3/7.7 increases with sSFR and star-formation surface density, while 6.2/7.7 decreases with sSFR, consistent with preferential processing of small ionized PAH carriers. ASPECS-15, the AGN-hosting source, has the lowest 6.2/7.7 ratio and highest sSFR, suggesting a reduced contribution from small PAHs, potentially due to AGN activity. The 7.7 micron luminosity follows the local L7.7-SFR relation, supporting its use as a star-formation tracer at z ~ 1. Conclusions. PAH emission at cosmic noon appears shaped by different ISM conditions than in nearby starburst galaxies, likely reflecting more intense radiation fields, while the 7.7 micron feature remains a robust SFR tracer.
Source: arXiv (Cornell University)
Authors: Lofaro, Cristina Maria, Santos, Tanio Díaz, Shivaei, Irene, Boogaard, Leindert A., Sandstrom, Karin, Donnan, Fergus R., Aravena, Manuel, Pérez-González, Pablo G., Aranda, Román Fernández, Decarli, Roberto, Galliano, Frédéric, Inami, Hanae, Östlin, Göran, Popping, Gergö, van der Werf, Paul, Walter, Fabian
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Aeronautics and Space Administration, Comunidad de Madrid, Space Telescope Science Institute, Agence Nationale de la Recherche, Centre National d’Etudes Spatiales, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Centre National de la Recherche Scientifique, Hellenic Foundation for Research and Innovation, Agencia Nacional de Investigación y Desarrollo, Institut National de Physique Nucléaire et de Physique des Particules
Awards: G103270039, G1338664626, G1424166960, G2421315707, G2428672771, G256731684, G39472684, MILLENIUM NUCLEUS FOR GALAXIES, G5084717281, G5568641063, G6662351857, Revealing dust Evolution - Depletion, Emission and Extinction Modeling In Nearby Galaxies (REDEEMING), 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: W7164999600