2025A&A...704A..71K

Context. We investigated the James Webb Space Telescope photometric color classification of mid-infrared (MIR) selected galaxies at high redshifts, toward cosmic noon.
Aims. The aim of the present work is to obtain a z-dependent mid-infrared (MIR) photometric galaxy classification tool based on broad spectral emission and absorption lines using the JWST Mid-Infrared Instrument (MIRI) and its broadband filters.
Methods. We used the largest Spitzer MIR spectral database to obtain synthetic photometry in the JWST/MIRI filters. We formed MIRI filter combinations to trace the strong polycyclic aromatic hydrocarbon (PAH) emission features and the 9.7 μm silicate feature in seven redshift windows from z = 0.25 - 2.10.
Results. We present z-dependent MIRI color-color plots that separate active galactic nuclei (AGN), star-forming galaxies (SFGs), and silicate absorption-dominated galaxies up to z ∼ 2. We applied the photometric MIR colors to the largest (∼34 arcmin²) MIRI survey called the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES), to identify AGN, SFGs, and Si-absorption dominated galaxies out to substantial redshifts. Our JWST/MIRI SFGs sample includes galaxies with total IR luminosities of 10^9.2 ∼ 10^11.9L_⊙ at 0.9 ≤ z < 1.57. The majority of them are consistent with the z ∼ 1 main sequence. We also identified the first examples of z ∼ 1 galaxies with deep silicate absorption.