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Arxiv: Dust attenuation evolution in z \sim 2-12 JWST galaxies Published: 2/8/2024 9:00:01 PM Updated: 2/8/2024 9:00:01 PM

Paper abstract: A sizable fraction of the heavy elements synthesized by stars in galaxiescondenses into sub-micron-sized solid-state particles, known as dust grains.Dust produces a wavelength-dependent attenuation, A_\lambda, of the galaxyemission, thereby significantly altering its observed properties. Locally,A_\lambda is in general the sum of a power-law and a UV feature ('bump')produced by small, carbon-based grains. However, scant information existsregarding its evolution across cosmic time. Here, leveraging data from 173galaxies observed by the James Webb Space Telescope in the redshift range z = 2- 12, we report the most distant detection of the UV bump in a z ~ 7.55 galaxy(when the Universe was only ~ 700 Myr old), and show for the first time thatthe power-law slope and the bump strength decrease towards high redshifts. Wepropose that the flat A_\lambda shape at early epochs is produced by largegrains newly formed in supernova ejecta, which act as the main dust factoriesat such early epochs. Importantly, these grains have undergone minimalreprocessing in the interstellar medium due to the limited available cosmictime. This discovery opens new perspectives in the study of cosmic dust originand evolution.