Little Red Dot Cosmology: A Matter-Era Baryon Acoustic Oscillations Probe of ΛCDM
Abstract
The discovery of Little Red Dots (LRDs) with JWST provides a new source population for cosmology in a largely unmapped period of cosmic history. LRDs are most numerous at 4≲ z≲9, thereby bridging existing low-redshift large-scale-structure measurements and the cosmic microwave background. In this epoch, the Universe is deep in the matter-dominated era, where dark energy is dynamically negligible and the expansion history is tightly predicted in ΛCDM, making these redshifts a clean test of the standard cosmological model. Recent measurements indicate that LRDs have number densities of n̅∼10−4 h3 Mpc−3, a bias rising from b∼ 3 to ∼8 over this interval, and distinctive spectrophotometric signatures -- a remarkably favorable combination for baryon acoustic oscillation (BAO) measurements. Using a Fisher forecast with these fiducial inputs, we find that a wide-field spectroscopic survey of LRDs over a DESI-like (14,000 deg2) footprint delivers a percent-level isotropic distance scale measurement of DV/rd across four bins spanning 4≲ z≲9. LRDs are therefore a compelling target for future wide-field near- to mid-infrared spectroscopy aimed at mapping large-scale structure deep into the matter-dominated era.
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BibTeX
@misc{zebrowski2026little,
title = {{Little Red Dot Cosmology: A Matter-Era Baryon Acoustic Oscillations Probe of $Λ$CDM}},
author = {Jessica A. Zebrowski and Rohan P. Naidu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.06926},
eprint = {2609.06926},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06926},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Little Red Dot Cosmology: A Matter-Era Baryon Acoustic Oscillations Probe of ΛCDM
AU - Jessica A. Zebrowski
AU - Rohan P. Naidu
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.06926
UR - https://arxiv.org/abs/2609.06926
AB - The discovery of Little Red Dots (LRDs) with JWST provides a new source population for cosmology in a largely unmapped period of cosmic history. LRDs are most numerous at 4≲ z≲9, thereby bridging existing low-redshift large-scale-structure measurements and the cosmic microwave background. In this epoch, the Universe is deep in the matter-dominated era, where dark energy is dynamically negligible and the expansion history is tightly predicted in ΛCDM, making these redshifts a clean test of the standard cosmological model. Recent measurements indicate that LRDs have number densities of n̅∼10^−4 h^3 Mpc^−3, a bias rising from b∼ 3 to ∼8 over this interval, and distinctive spectrophotometric signatures -- a remarkably favorable combination for baryon acoustic oscillation (BAO) measurements. Using a Fisher forecast with these fiducial inputs, we find that a wide-field spectroscopic survey of LRDs over a DESI-like (14,000 deg^2) footprint delivers a percent-level isotropic distance scale measurement of D_V/r_d across four bins spanning 4≲ z≲9. LRDs are therefore a compelling target for future wide-field near- to mid-infrared spectroscopy aimed at mapping large-scale structure deep into the matter-dominated era.
ER -