A Population of Little Red Dot-like Quasars in SDSS
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 AGN templates. Local LRD-like objects allow for detailed studies of the underlying physical processes with archival multi-wavelength datasets unavailable in the high-z Universe. We show that the 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) which 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 [NeV]λ3426 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 NIR. 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%.
Related
- An ALMA Band 7 survey of SDSS/Herschel quasars in Stripe 82: II. The nature of FIR-bright quasars
- Little Red and Blue Dots: AGN-excited narrow lines, Lyman-α emission, and resemblance to standard quasars
- Luminosity Function of Quasars at 1.0 < z < 3.5 from SDSS and DESI
- An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN – radiation-driven outflows in little red dots, quasars and variable stars
- The Lumina Project: The Demographics of Active Galactic Nuclei from Quasars to Little Red Dots at z ≥ 3
BibTeX
@misc{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},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.26098},
eprint = {2606.26098},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.26098},
note = {CC BY 4.0},
}
RIS
TY - UNPB
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 - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2606.26098
UR - https://arxiv.org/abs/2606.26098
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 AGN templates. Local LRD-like objects allow for detailed studies of the underlying physical processes with archival multi-wavelength datasets unavailable in the high-z Universe. We show that the 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) which 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 [NeV]λ3426 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 NIR. 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%.
ER -