Little Red Dots with Broad Hβ Lines Reveal the Black Hole Mass Function at 7<z<9.5
Abstract
We present a systematic search for broad Hβ emission at 7<z<9.5 in 21,770 JWST/NIRSpec PRISM spectra drawn from four blank fields and six lensing clusters with photometry spanning 1942 arcmin2. We find a sample of 20 sources with statistically significant broad-Hβ emission, including 13 new sources. Our entire sample has colors and morphologies consistent with little red dots (LRDs), compared to only 37\% of broad-line emitters at 3.5<z<6. Interpreting the broad-lines as indicators of Broad-line Active Galactic Nuclei (BLAGN), we infer black hole masses of 4.2×106−2.1×108\,M⊙. We calculate completeness corrections and construct the black hole mass function at z∼8. The normalization of the black hole mass function rises by ≈1.0~dex from z∼8−5, consistent with average black hole growth at fEdd≈0.1. Comparing with cosmological simulations, the z∼8 black hole mass function requires heavy (105\,M⊙) seeds or super-Eddington accretion onto light or intermediate mass seeds to match its normalization. Finally, we infer bolometric luminosities for the sample and construct a bolometric luminosity function. We integrate over this luminosity function to derive a black hole accretion density (BHAD) of 4.8+5.8−2.6×10−7 M⊙ yr−1 Mpc−3, showing broad agreement with previous photometric work, but disagreement with previous X-ray models, reinforcing the idea that BLAGN are more common in the early universe than previously expected.
Related
- Wings of little dots: Exponential broad lines from a stratified broad-line region
- Where did all the Little Red Dots go? The abundance of LRD analogues among objects with broad lines at z < 0.35
- A new sample of Little Red Dots at z<0.45 in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability
- Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots
- UV spectra of little red dots: Broad-line N/C, gas recycling and black hole masses
BibTeX
@misc{taylor2026little,
title = {{Little Red Dots with Broad H$β$ Lines Reveal the Black Hole Mass Function at 7<z<9.5}},
author = {Anthony J. Taylor and Steven L. Finkelstein and Hollis B. Akins and Vasily Kokorev and Pablo Arrabal Haro and Sophie Koudmani and Caitlin M. Casey and Mark Dickinson and Junehyoung Jeon and Madisyn Brooks and Volker Bromm and Christopher J. Conselice and Kelcey Davis and Callum T. Donnan and Andreas L. Faisst and Seiji Fujimoto and Lukas J. Furtak and Mauro Giavalisco and Ansh R. Gupta and Michaela Hirschmann and Tiger Yu-Yang Hsiao and Dale D. Kocevski and Anton M. Koekemoer and Gene C. K. Leung and Ray A. Lucas and Lorenzo Napolitano and Casey Papovich and Laura Pentericci and Pablo G. Perez-Gonzalez and Rachel S. Somerville and Fabian Walter and L. Y. Aaron Yung},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37564},
eprint = {2610.37564},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37564},
}
RIS
TY - UNPB
TI - Little Red Dots with Broad Hβ Lines Reveal the Black Hole Mass Function at 7<z<9.5
AU - Anthony J. Taylor
AU - Steven L. Finkelstein
AU - Hollis B. Akins
AU - Vasily Kokorev
AU - Pablo Arrabal Haro
AU - Sophie Koudmani
AU - Caitlin M. Casey
AU - Mark Dickinson
AU - Junehyoung Jeon
AU - Madisyn Brooks
AU - Volker Bromm
AU - Christopher J. Conselice
AU - Kelcey Davis
AU - Callum T. Donnan
AU - Andreas L. Faisst
AU - Seiji Fujimoto
AU - Lukas J. Furtak
AU - Mauro Giavalisco
AU - Ansh R. Gupta
AU - Michaela Hirschmann
AU - Tiger Yu-Yang Hsiao
AU - Dale D. Kocevski
AU - Anton M. Koekemoer
AU - Gene C. K. Leung
AU - Ray A. Lucas
AU - Lorenzo Napolitano
AU - Casey Papovich
AU - Laura Pentericci
AU - Pablo G. Perez-Gonzalez
AU - Rachel S. Somerville
AU - Fabian Walter
AU - L. Y. Aaron Yung
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37564
UR - https://arxiv.org/abs/2610.37564
AB - We present a systematic search for broad Hβ emission at 7<z<9.5 in 21,770 JWST/NIRSpec PRISM spectra drawn from four blank fields and six lensing clusters with photometry spanning 1942 arcmin^2. We find a sample of 20 sources with statistically significant broad-Hβ emission, including 13 new sources. Our entire sample has colors and morphologies consistent with little red dots (LRDs), compared to only 37\% of broad-line emitters at 3.5<z<6. Interpreting the broad-lines as indicators of Broad-line Active Galactic Nuclei (BLAGN), we infer black hole masses of 4.2×10^6−2.1×10^8\,M_⊙. We calculate completeness corrections and construct the black hole mass function at z∼8. The normalization of the black hole mass function rises by ≈1.0~dex from z∼8−5, consistent with average black hole growth at f_Edd≈0.1. Comparing with cosmological simulations, the z∼8 black hole mass function requires heavy (10^5\,M_⊙) seeds or super-Eddington accretion onto light or intermediate mass seeds to match its normalization. Finally, we infer bolometric luminosities for the sample and construct a bolometric luminosity function. We integrate over this luminosity function to derive a black hole accretion density (BHAD) of 4.8^+5.8_−2.6×10^−7 M_⊙ yr^−1 Mpc^−3, showing broad agreement with previous photometric work, but disagreement with previous X-ray models, reinforcing the idea that BLAGN are more common in the early universe than previously expected.
ER -