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Peer-reviewedCC BY 4.0The Astrophysical Journal

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

  • Quinn O. Casey1
  • Ryan C. Hickox1
  • Nikko J. Cleri2
  • Jonathan H. Cohn1
  • David M. Alexander3
  • Emmanuel Durodola1
  • Kelly E. Whalen4,5
  • Raphael E. Hviding6
  • Tonima Tasnim Ananna7
7 affiliations
  1. 1Dartmouth College
  2. 2The Pennsylvania State University
  3. 3Durham University
  4. 4NASA Goddard Space Flight Center
  5. 5Oak Ridge Associated Universities
  6. 6Max-Planck-Institut für Astronomie
  7. 7Wayne State University
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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%.

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Cite

BibTeXRIS
BibTeX
@article{casey2026population,
  title = {{A Population of Little Red Dot-like Quasars in SDSS*}},
  author = {Quinn O. Casey and Ryan C. Hickox and Nikko J. Cleri and Jonathan H. Cohn and David M. Alexander and Emmanuel Durodola and Kelly E. Whalen and Raphael E. Hviding and Tonima Tasnim Ananna},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = sep,
  doi = {10.3847/1538-4357/aea419},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea419},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - A Population of Little Red Dot-like Quasars in SDSS*
AU  - Quinn O. Casey
AU  - Ryan C. Hickox
AU  - Nikko J. Cleri
AU  - Jonathan H. Cohn
AU  - David M. Alexander
AU  - Emmanuel Durodola
AU  - Kelly E. Whalen
AU  - Raphael E. Hviding
AU  - Tonima Tasnim Ananna
PY  - 2026
DA  - 2026/09/30
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea419
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea419
AB  - 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%.
SN  - 0004-637X
SN  - 1538-4357
ER  -