5-25 $\mu$m Galaxy Number Counts from Deep JWST Data

TL;DR

This paper presents deep galaxy number counts in eight mid-infrared bands from JWST and other surveys, revealing discrepancies with galaxy formation models and measuring the cosmic infrared background.

Contribution

It provides the deepest mid-infrared galaxy counts to date, combining JWST, Spitzer, and AKARI data, and compares these counts to theoretical models.

Findings

Counts extend over 3-5 orders of magnitude in flux.

Discrepancies observed between counts and semi-analytical models.

Measured cosmic infrared background fluxes are consistent with previous surveys.

Abstract

Galaxy number counts probe the evolution of galaxies over cosmic time, and serve as a valuable comparison point to theoretical models of galaxy formation. We present new galaxy number counts in eight photometric bands between 5 and 25 $\mu$m from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES) and the JWST Advanced Deep Extragalactic Survey (JADES) deep MIRI parallel, extending to unprecedented depth. By combining our new MIRI counts with existing data from Spitzer and AKARI, we achieve counts across 3-5 orders of magnitude in flux in all MIRI bands. Our counts diverge from predictions from recent semi-analytical models of galaxy formation, likely owing to their treatment of mid-infrared aromatic features. Finally, we integrate our combined JWST-Spitzer counts at 8 and 24 $\mu$m to measure the cosmic infrared background (CIB) light at these wavelengths; our measured CIB fluxes are consistent with those from previous mid-infrared surveys, but larger than predicted by some models based on TeV blazar data.