Reduced incidence of little red dots at z < 3 based on number density and halo mass evolution
Abstract
An intriguing puzzle in extragalactic astronomy is the scarcity of Little Red Dots (LRDs) at z < 3, compared to their higher abundance at earlier cosmic epochs. To investigate this, we measure the overdensity for 98 specpically confirmed LRDs at 3<z<7, and find that these LRDs predominantly reside in under-dense regions at z > 4 but shift to more typical galaxy environments at z ∼ 3.5. Concurrently, cross-correlation analyses show that their dark matter halo masses grow rapidly, from ≲ 1010.1 M⊙ at z ∼ 7.5 to ∼ 1011.3 M⊙ at z ∼ 3.5, approaching the halo masses of normal galaxies at lower redshifts. Applying an empirical stellar-to-halo mass scaling relation, we find that LRDs still host over-massive black holes relative to their stellar masses at z > 4, yet converge toward the local BH-stellar mass relation at lower redshifts. The coherent evolution of LRDs' large-scale environments and halo masses toward those of normal galaxies provides a plausible explanation for their declining abundance at z < 3, even though the underlying small-scale physical mechanisms remain elusive.
Versions
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BibTeX
@misc{zhang2026reduced,
title = {{Reduced incidence of little red dots at z < 3 based on number density and halo mass evolution}},
author = {Chenxuan Zhang and Huanian Zhang and Qingwen Wu and Luis C. Ho and Jian-Min Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.02773},
eprint = {2606.02773},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.02773},
}
RIS
TY - UNPB
TI - Reduced incidence of little red dots at z < 3 based on number density and halo mass evolution
AU - Chenxuan Zhang
AU - Huanian Zhang
AU - Qingwen Wu
AU - Luis C. Ho
AU - Jian-Min Wang
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2606.02773
UR - https://arxiv.org/abs/2606.02773
AB - An intriguing puzzle in extragalactic astronomy is the scarcity of Little Red Dots (LRDs) at z < 3, compared to their higher abundance at earlier cosmic epochs. To investigate this, we measure the overdensity for 98 specpically confirmed LRDs at 3<z<7, and find that these LRDs predominantly reside in under-dense regions at z > 4 but shift to more typical galaxy environments at z ∼ 3.5. Concurrently, cross-correlation analyses show that their dark matter halo masses grow rapidly, from ≲ 10^10.1 M_⊙ at z ∼ 7.5 to ∼ 10^11.3 M_⊙ at z ∼ 3.5, approaching the halo masses of normal galaxies at lower redshifts. Applying an empirical stellar-to-halo mass scaling relation, we find that LRDs still host over-massive black holes relative to their stellar masses at z > 4, yet converge toward the local BH-stellar mass relation at lower redshifts. The coherent evolution of LRDs' large-scale environments and halo masses toward those of normal galaxies provides a plausible explanation for their declining abundance at z < 3, even though the underlying small-scale physical mechanisms remain elusive.
ER -