Work

A Population of Little Red Dot-like Quasars in SDSS*

Year: 2026

Type: article

Abstract: Compact and red sources in the high-redshift ( z ∼ 5) Universe, known as “Little Red Dots” (LRDs), are among JWST’s most intriguing discoveries. These sources have broad Balmer emission lines, weak X-ray emission, and unique spectral energy distributions (SEDs) poorly fit by either stellar or active galactic nucleus (AGN) templates. Local LRD-like objects allow for detailed studies of the underlying physical processes with archival multiwavelength datasets unavailable in the high- z Universe. We show that the Sloan Digital Sky Survey (SDSS) ugriz filters at z ≈ 0.4, 0.8 overlap well with the JWST filters used to select LRDs at z ∼ 5. We use SDSS quasars to define a sample of ∼1300 Local Red Dots (LoRDs) that share the same photometric colors of LRDs. A subset of the LoRD sample selected to have V-shaped continua ( N = 244) show prominent higher-order Balmer absorption features and [Ne v ] λ 3426 emission, both of which would likely be missed in JWST/PRISM observations given the low spectral resolution. A composite SED of the LoRDs differs from a typical quasar SED in the rest-frame UV/optical, but the two agree with each other in the near-infrared. The LoRD SED matches well with a stack of LRDs and can be modeled either as a reddened AGN combined with a host galaxy, or as a reddened AGN combined with a host galaxy and a cool blackbody. Interestingly, the LoRDs are X-ray detected at a rate comparable to typical quasars. However, the probability that LoRDs and typical quasars would go undetected, if subject to the LRD X-ray upper limits, is >50%.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/aea419