A First Look into the Nature of JWST/MIRI 7.7 μm Sources from SMACS 0723

Abstract Until now, our knowledge of the extragalactic universe at mid-infrared (mid-IR) wavelengths (>5 μ m) was limited to rare active galactic nuclei and brightest normal galaxies up z ∼ 3. The advent JWST with its Mid-Infrared Instrument (MIRI) will revolutionize ability mid-IR regime as a key wavelength domain probe high- universe. In this work we present first study MIRI 7.7 m sources selected >3 σ significance from lensing cluster field SMACS J0723.3-7327. We model their spectral energy distribution (SED) fitting 13 Hubble Space Telescope broad bands, in order obtain photometric redshifts derived physical parameters for all these sources. find that galaxy sample is mainly composed = 4 has tail about 2% higher ≈ 9–10. vast majority have [3.6]–[7.7] < 0 colors very few them need high dust extinction values ( A V 3–6 mag) SED fitting. resulting lensing-corrected stellar masses span range 10 7 –10 11 M ⊙ . Overall, results clearly show observations deep fields are already useful high-redshift suggest deeper be available soon open up, time, epoch reionization wavelengths.