An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN – radiation-driven outflows in little red dots, quasars and variable stars
12 affiliations
- 1Kavli Institute for Cosmology, University of Cambridge , Madingley Road, Cambridge, CB3 0HA ,
- 2Cavendish Laboratory, University of Cambridge , 19 JJ Thomson Avenue, Cambridge, CB3 0HE ,
- 3University College London Department of Physics and Astronomy, , Gower Street, London WC1E 6BT ,
- 4Université degli Studi di Firenze Dipartimento di Fisica e Astronomia, , Via G. Sansone 1,I-50019, Sesto Fiorentino, Firenze ,
- 5INAF - Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5, I-50125, Firenze ,
- 6University of Oxford Department of Physics, , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH ,
- 7Scuola Normale Superiore , Piazza dei Cavalieri 7, I-56126 Pisa ,
- 8Astronomy and Mathematics Centre for Astrophysics Research, Department of Physics, , University of Hertfordshire, Hatfield AL10 9AB ,
- 9Steward Observatory, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85721 ,
- 10Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, Maryland 21218 ,
- 11University of California Department of Astronomy and Astrophysics , Santa Cruz, 1156 High Street, Santa Cruz CA 96054 ,
- 12Max-Planck-Institut für extraterrestrische Physik (MPE) , Gießenbachstraße 1, 85748 Garching ,
Abstract
A notable achievement of the first generation of JWST surveys was the discovery of an abundance of faint high-redshift (z > 4) broad-line active galactic nuclei (AGN) in the Lbol < 1045 erg s−1 regime, previously only accessible at z < 1. The high prevalence of absorption features in their broad hydrogen lines is one of the peculiarities of a significant fraction of this new population. In this paper, we conduct a broad census of Balmer absorption in a sample of 47 Type-1 AGN spanning 2 < z < 7. Accounting for incompleteness of JWST spectroscopic data, we estimate that 44−6+21 % of Little Red Dots (LRDs) have absorption in Hα while the incidence rate is <25 % (at 2σ) in Little Blue Dots (LBDs). Additionally, R1000 JWST/NIRSpec data is strongly resolution limited, implying an inability to disentangle Doppler broadening in the absorption from optical depth effects. This is alleviated with R2700 observations, although some degeneracies remain. We find a significant correlation between the velocity of the Balmer absorption and the [OIII]5007 narrow line luminosity, suggesting a common driving mechanism. We do not find any other significant correlations (and do not confirm previously claimed correlations) between Balmer absorption and other spectral properties of LRDs (except for the expected correlation between Hα and Hβ absorption velocities). Comparing LRDs, quasars and stellar Hα absorbers, we establish that absorption in both LRDs and broad absorption line quasars is consistent with radiatively driven outflows, echoing the physics of variable stars yet occurring at vastly different scales.
Related
- The obscured nucleus of NGC 3256,S. I. Anisotropic active galactic nucleus near-IR radiation field traced by CO v=1--0 with JWST NIRSpec
- Radiation hydrodynamics of star–disc collisions: From system parameters to outflows and light curves
- Studying Outflows with Synthetic Absorption Line Spectra from High Resolution Simulations
- The WISSH quasars project XIII. A multi-epoch study of ultra-fast broad absorption line outflows at cosmic noon
- Radiation-hydrodynamics of star-disc collisions: From system parameters to outflows and lightcurves
BibTeX
@article{juodzbalis2026incomplete,
title = {{An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN – radiation-driven outflows in little red dots, quasars and variable stars}},
author = {Ignas Juodz̭balis and Xihan Ji and Francesco D’Eugenio and Jan Scholtz and Roberto Maiolino and Amanda Stoffers and Alessandro Marconi and Elena Bertola and Andrew J Bunker and Stefano Carniani and Giovanni Cresci and Emma Curtis-Lake and Zheng Ma and Cosimo Marconcini and Eleonora Parlanti and Pierluigi Rinaldi and Brant Robertson and Hannah Übler and Giacomo Venturi and Junyu Zhang},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = nov,
doi = {10.1093/mnras/stag2131},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2131/9017889},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN – radiation-driven outflows in little red dots, quasars and variable stars
AU - Ignas Juodz̭balis
AU - Xihan Ji
AU - Francesco D’Eugenio
AU - Jan Scholtz
AU - Roberto Maiolino
AU - Amanda Stoffers
AU - Alessandro Marconi
AU - Elena Bertola
AU - Andrew J Bunker
AU - Stefano Carniani
AU - Giovanni Cresci
AU - Emma Curtis-Lake
AU - Zheng Ma
AU - Cosimo Marconcini
AU - Eleonora Parlanti
AU - Pierluigi Rinaldi
AU - Brant Robertson
AU - Hannah Übler
AU - Giacomo Venturi
AU - Junyu Zhang
PY - 2026
DA - 2026/11/06
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag2131
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2131/9017889
AB - A notable achievement of the first generation of JWST surveys was the discovery of an abundance of faint high-redshift (z > 4) broad-line active galactic nuclei (AGN) in the Lbol < 1045 erg s−1 regime, previously only accessible at z < 1. The high prevalence of absorption features in their broad hydrogen lines is one of the peculiarities of a significant fraction of this new population. In this paper, we conduct a broad census of Balmer absorption in a sample of 47 Type-1 AGN spanning 2 < z < 7. Accounting for incompleteness of JWST spectroscopic data, we estimate that 44_−6^+21 % of Little Red Dots (LRDs) have absorption in Hα while the incidence rate is <25 % (at 2σ) in Little Blue Dots (LBDs). Additionally, R1000 JWST/NIRSpec data is strongly resolution limited, implying an inability to disentangle Doppler broadening in the absorption from optical depth effects. This is alleviated with R2700 observations, although some degeneracies remain. We find a significant correlation between the velocity of the Balmer absorption and the [OIII]5007 narrow line luminosity, suggesting a common driving mechanism. We do not find any other significant correlations (and do not confirm previously claimed correlations) between Balmer absorption and other spectral properties of LRDs (except for the expected correlation between Hα and Hβ absorption velocities). Comparing LRDs, quasars and stellar Hα absorbers, we establish that absorption in both LRDs and broad absorption line quasars is consistent with radiatively driven outflows, echoing the physics of variable stars yet occurring at vastly different scales.
SN - 0035-8711
SN - 1365-2966
ER -