Red Spiral Galaxies at Cosmic Noon Unveiled in the First JWST Image

Abstract

In the first image of the James Webb Space Telescope (JWST) of SMACS J0723.3-7327, one of the most outstanding features is the emergence of a large number of red spiral galaxies, because such red spiral galaxies are only a few percent in the number fraction among nearby spiral galaxies. While these apparently red galaxies were already detected with the Spitzer Space Telescope at ∼3–4 μm, the revolutionized view from the JWST’s unprecedented spatial resolution has unveiled their hidden spiral morphology for the first time. Within the red spiral galaxies, we focus on the two reddest galaxies that are very faint in the <0.9 μ m bands and show red colors in the 2–4 μm bands. Our study finds that the two extremely red spiral galaxies are likely to be in the cosmic noon (1 < z < 3). One of the extremely red spiral galaxies is more likely to be a passive galaxy having moderate dust reddening (i.e., ∼zero star formation rate with AV ~ 1 mag). The other is consistent with both passive and dusty starburst solutions (i.e., star formation rate > 100 M⊙ yr−1 with AV ∼ 3 mag). These “red spiral” galaxies would be an interesting, potentially new population of galaxies, as we start to see their detailed morphology using the JWST, for the first time.