James Webb Space Telescope Feed Post

Harvard ADS: UNCOVER: Significant Reddening in Cosmic Noon Quiescent Galaxies

Paper abstract: We explore the physical properties of five massive quiescent galaxies at z~2.5, revealing the presence of non-negligible dust reservoirs. JWST NIRSpec observations were obtained for each target, finding no significant line emission; multiple star formation tracers independently place upper limits between 0.1-10~M_\odot / \mathrm{yr}. Spectral energy distribution modeling with Prospector infers stellar masses between \log_{10}[M / M_\odot] ~ 10-11 and stellar mass-weighted ages between 1-2 Gyr. The inferred mass-weighted effective radii (r_{eff}~ 0.4-1.4 kpc) and inner 1 kpc stellar surface densities (\log_{10}[\Sigma / M_\odot \mathrm{kpc}^2 ]\gtrsim 9) are typical of quiescent galaxies at z \gtrsim 2. The galaxies display negative color gradients (redder core and bluer outskirts); for one galaxy, this effect results from a dusty core, while for the others it may be evidence of an "inside-out" growth process. Unlike local quiescent galaxies, we identify significant reddening in these typical cosmic noon passive galaxies; all but one require A_V \gtrsim 0.4. This finding is in qualitative agreement with previous studies but our deep 20-band NIRCam imaging is able to significantly suppress the dust-age degeneracy and confidently determine that these galaxies are reddened. We speculate about the physical effects that may drive the decline in dust content in quiescent galaxies over cosmic time.