Delving deep : a population of extremely dusty dwarfs observed by JWST

Abstract

Aims. We take advantage of the NIRCam photometric observations available as part of the Cosmic Evolution Early Release Science survey (CEERS) to identify and analyse very red sources in an effort to discover very dusty star forming galaxies.

Methods. We select red galaxies as objects with a S/N > 3 at 4.4 μm and a S/N < 2 in all JWST and HST filters at λ ≤ 2 μm, which corresponds to [F200W]−[F444W]> 1.2 considering CEERS depths. This selection is ideal to identify very dusty (AV > 1 mag) galaxies with stellar masses between 106 and 1010 M⊙ at z < 5, more massive dusty galaxies at z = 5 − 18 and galaxies at z > 18 due to the Lyman absorption, independently of their dust extinction.

Results. Our sample of F200W-dropouts contains no strong candidates at z > 6.5, instead it consists almost completely (∼81%) of z < 2 low-mass galaxies, with a median stellar mass of 107.3 M⊙. These galaxies show an exceptional dust extinction with median value of AV = 4.9 mag, completely unexpected given their low stellar mass. The remaining galaxies, which are at z < 6.5, show similar large dust extinction (AV > 1), but they are generally more massive > 107.5 M⊙.