A new sample of Little Red Dots at z<0.45 in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability
4 affiliations
- 1Institute of Science and Technology Austria (ISTA) , Am Campus 1 , 3400 Klosterneuburg , Austria
- 2MIT Kavli Institute for Astrophysics and Space Research , 70 Vassar Street , Cambridge , MA 02139 , USA
- 3Center for Astrophysics , Harvard & Smithsonian , 60 Garden St , Cambridge , MA 02138 , USA
- 4Max-Planck-Institut für Astronomie , Königstuhl 17 , D-69117 Heidelberg , Germany
Abstract
JWST has unveiled an abundant population of compact broad-line emitters largely at z≳4, the Little Red Dots (LRDs), which might represent a previously unprobed supermassive black hole evolution channel predominant at high redshift. However, the LRDs have remained mostly elusive at lower redshift (z≲2) where detailed studies are possible from ground-based observatories. We searched for low-redshift LRDs in the Dark Energy Spectroscopic Instrument (DESI) survey. Our search is primarily based on emission line properties, as opposed to earlier approaches that searched for compact sources with specific photometric spectral energy distributions. We report the discovery of eight LRDs at z=0.2−0.45, which show spectral features akin to the high-redshift LRDs in the rest-frame optical. The sources are characterized by broad Balmer lines, steep Balmer decrements, compact morphologies, Balmer absorption features and/or strong He I emission, but weak or absent He II, [Ne V] or other high excitation lines typical of Type I AGN. For 7 out of 8 sources, we retrieve dense-cadence light curves from time-domain surveys and for most sources we find weak to no intrinsic variability (0.0−0.1 mag) over 4−17 years in the rest-frame. We also highlight the identification of a quasar with similar Balmer line profiles as LRDs, but shows differences in Balmer decrement, significant variability, and high-ionisation lines. Given the effective volume 4.9Gpc3 covered by DESI DR1 at z<0.45, our sample corresponds to a number density of 1.6×10−9Mpc−3, indicating a number density ∼10,000 times lower than in the first billion years of cosmic time. We find a dearth of luminous and red LRDs at z<1 compared to higher-redshift, which could suggest lower gas feeding rates of LRD activity due to higher metallicities at later cosmic epochs.
Related
- The Balmer Absorber Strength Problem of Little Red Dots
- Origins of the UV Continuum and Balmer Emission Lines in Little Red Dots: Observational Validation of Dense Gas Envelope Models Enshrouding the Active Galactic Nucleus
- An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN – radiation-driven outflows in little red dots, quasars and variable stars
- A Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7
- Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots
BibTeX
@misc{park2026sample,
title = {{A new sample of Little Red Dots at $z<0.45$ in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability}},
author = {Kevin Park and Alberto Torralba and Jorryt Matthee and Sara Mascia and Zoltán Haiman and Rohan P. Naidu and Anna de Graaff},
howpublished = {arXiv (Cornell University)},
year = {2026},
month = may,
doi = {10.48550/arxiv.2605.14233},
url = {https://arxiv.org/abs/2605.14233},
note = {CC BY},
}
RIS
TY - UNPB
TI - A new sample of Little Red Dots at z<0.45 in DESI DR1: Broad Balmer lines, low ionization spectrum and no variability
AU - Kevin Park
AU - Alberto Torralba
AU - Jorryt Matthee
AU - Sara Mascia
AU - Zoltán Haiman
AU - Rohan P. Naidu
AU - Anna de Graaff
PY - 2026
DA - 2026/05/14
PB - arXiv (Cornell University)
DO - 10.48550/arxiv.2605.14233
UR - https://arxiv.org/abs/2605.14233
AB - JWST has unveiled an abundant population of compact broad-line emitters largely at z≳4, the Little Red Dots (LRDs), which might represent a previously unprobed supermassive black hole evolution channel predominant at high redshift. However, the LRDs have remained mostly elusive at lower redshift (z≲2) where detailed studies are possible from ground-based observatories. We searched for low-redshift LRDs in the Dark Energy Spectroscopic Instrument (DESI) survey. Our search is primarily based on emission line properties, as opposed to earlier approaches that searched for compact sources with specific photometric spectral energy distributions. We report the discovery of eight LRDs at z=0.2−0.45, which show spectral features akin to the high-redshift LRDs in the rest-frame optical. The sources are characterized by broad Balmer lines, steep Balmer decrements, compact morphologies, Balmer absorption features and/or strong He I emission, but weak or absent He II, [Ne V] or other high excitation lines typical of Type I AGN. For 7 out of 8 sources, we retrieve dense-cadence light curves from time-domain surveys and for most sources we find weak to no intrinsic variability (0.0−0.1 mag) over 4−17 years in the rest-frame. We also highlight the identification of a quasar with similar Balmer line profiles as LRDs, but shows differences in Balmer decrement, significant variability, and high-ionisation lines. Given the effective volume 4.9Gpc^3 covered by DESI DR1 at z<0.45, our sample corresponds to a number density of 1.6×10^−9Mpc^−3, indicating a number density ∼10,000 times lower than in the first billion years of cosmic time. We find a dearth of luminous and red LRDs at z<1 compared to higher-redshift, which could suggest lower gas feeding rates of LRD activity due to higher metallicities at later cosmic epochs.
SN - 2331-8422
ER -