Similarity between compact extremely red objects discovered with JWST in cosmic dawn and blue-excess dust-obscured galaxies known in cosmic noon

Abstract

Spatially compact objects with extremely red color in the rest-frame optical to near-infrared (0.4--1 $\mu \mathrm{m}$) and blue color in the rest-frame ultraviolet (UV; 0.2--0.4 $\mu \mathrm{m}$) have been discovered at $5<z<9$ using the James Webb Space Telescope (JWST). These extremely red objects (JWST-EROs) exhibit spectral energy distributions (SEDs) that are difficult to explain using a single component of either star-forming galaxies or quasars, leading to two-component models in which the blue UV and extremely red optical are explained using less-dusty and dusty spectra of galaxies or quasars, respectively. Here, we report the remarkable similarity in SEDs between JWST-EROs and blue-excess dust-obscured galaxies (BluDOGs) identified at $2<z<3$. BluDOGs are a population of active galactic nuclei (AGNs) with blackhole masses of $\sim 10^{8-9}$ M${}_{\odot }$, which are one order of magnitude larger than those in some JWST-EROs. The Eddington ratios of BluDOGs are one or higher, whereas those of JWST-EROs are in the range of 0.1--1. Therefore, JWST-EROs are less massive, less active, and more common counterparts in higher-$z$ of BluDOGs in cosmic noon. Conversely, JWST-EROs have a significantly higher fraction of those with blue-excess than DOGs. We present the average UV spectra of BluDOGs as a comparison to JWST-EROs and discuss a coherent evolutionary scenario for dusty AGN populations.

10 pages, 5 figures, accepted for publication in ApJL