(LRDs)2: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample
8 affiliations
- 1Department of Astronomy , Tsinghua University , Beijing 100084 , China
- 2Steward Observatory , University of Arizona , 933 N. Cherry Ave. , Tucson , AZ 85721 , USA
- 3Center for Astrophysics | Harvard & Smithsonian , 60 Garden St. , Cambridge , MA 02138 , USA
- 4Chinese Academy of Sciences South America Center for Astronomy , National Astronomical Observatories , CAS , Beijing 100101 , China
- 5European Southern Observatory , Alonso de Córdova 3107 , Casilla 19001 , Vitacura , Santiago 19 , Chile
- 6Department of Astrophysical Sciences , Princeton University , 4 Ivy Lane , Princeton , NJ 08544 , USA
- 7Department of Astronomy , School of Physics , Peking University , Beijing 100871 , China
- 8Kavli Institute for Astronomy and Astrophysics , Peking University , Beijing 100871 , China
Abstract
JWST has revealed a substantial population of "Little Red Dots" (LRDs) at z>4, challenging conventional AGN frameworks. However, the low-redshift regime remains largely unexplored. In the second paper of the (LRDs)2 series, we present a systematic selection from DESI DR1 and identify 27 LRDs at z=0.2−0.9, yielding a number density lower limit of 7.5×10−10 cMpc−3. We conducted near-IR spectroscopic follow-up observations for 21 of them, revealing their full SED shapes and emission lines. These low-z LRDs share the hallmark properties of their high-z counterparts: compact morphology, V-shaped UV-optical continua, broad Balmer emission with extreme decrements (median Hα/Hβ∼15), frequent Balmer absorption (70%), and blackbody-like optical-to-near-IR continua. All have low metallicity, occupy the same regions in the BPT diagram as high-z LRDs, and have softer ionizing spectra than typical AGNs. The consistency between low-z and high-z LRD properties indicates the same physical processes at work. The correlation between broad-line Balmer luminosity and L5100 deviates from that of local type-1 AGNs, limiting the direct application of local BH mass calibrations. Ionized [O III] outflows are ubiquitous (78%). One LRD at z=0.196, J1717+3807, shows robust long-term variability in i and WISE bands. The optical-to-NIR continua of LRDs reveal a wide range of temperatures ∼2000−4700 K (peak 0.6−1.4 μm), with a subset showing cooler and larger envelopes than those at high z. Low-z LRDs serve not only as proximate laboratories for probing the nature of LRDs, but also trace the cosmic evolution of this population from the cosmic dawn to the present day.
Related
- A Spectral Framework for Testing the Quasi-Star Hypothesis in Little Red Dots I: Weighing LRDs by Their Super-Eddington Luminosity Ratios---No Signs of Overmassive Black Holes
- The Dance of the Little Red Dots: Spectroscopy of Two Blue Companions at z = 3.9 and 5.5 Reveals Young, Metal-Poor Starbursts Merging with Their LRDs within a Few Hundred Myr
- The THRILS Factor: Investigating the properties of Little Red Dots (LRDs) at 3<z<6 with JWST/NIRSpec
- A Cosmological Framework for Stellar Collisions at High Redshift in Proto-globular Clusters, Nuclear Star Clusters, and Little Red Dots
- A Vision for Little Red Dots in the Low-Redshift Universe with ALMA2040
BibTeX
@misc{lin2026lrds2,
title = {{(LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample}},
author = {Xiaojing Lin and Xiaohui Fan and Zheng Cai and Yichen Liu and Fengwu Sun and Fuyan Bian and Mingyu Li and Junjie Mao and Jenny E. Greene and Hanpu Liu and Jiaxuan Li and Weizhe Liu and Yilun Ma and Zechang Sun and Zijian Zhang},
howpublished = {arXiv},
year = {2026},
month = may,
doi = {10.48550/arxiv.2605.21574},
eprint = {2605.21574},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.21574},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - (LRDs)^2: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample
AU - Xiaojing Lin
AU - Xiaohui Fan
AU - Zheng Cai
AU - Yichen Liu
AU - Fengwu Sun
AU - Fuyan Bian
AU - Mingyu Li
AU - Junjie Mao
AU - Jenny E. Greene
AU - Hanpu Liu
AU - Jiaxuan Li
AU - Weizhe Liu
AU - Yilun Ma
AU - Zechang Sun
AU - Zijian Zhang
PY - 2026
DA - 2026/05/20
PB - arXiv
DO - 10.48550/arxiv.2605.21574
UR - https://arxiv.org/abs/2605.21574
AB - JWST has revealed a substantial population of "Little Red Dots" (LRDs) at z>4, challenging conventional AGN frameworks. However, the low-redshift regime remains largely unexplored. In the second paper of the (LRDs)^2 series, we present a systematic selection from DESI DR1 and identify 27 LRDs at z=0.2−0.9, yielding a number density lower limit of 7.5×10^−10 cMpc^−3. We conducted near-IR spectroscopic follow-up observations for 21 of them, revealing their full SED shapes and emission lines. These low-z LRDs share the hallmark properties of their high-z counterparts: compact morphology, V-shaped UV-optical continua, broad Balmer emission with extreme decrements (median Hα/Hβ∼15), frequent Balmer absorption (70%), and blackbody-like optical-to-near-IR continua. All have low metallicity, occupy the same regions in the BPT diagram as high-z LRDs, and have softer ionizing spectra than typical AGNs. The consistency between low-z and high-z LRD properties indicates the same physical processes at work. The correlation between broad-line Balmer luminosity and L_5100 deviates from that of local type-1 AGNs, limiting the direct application of local BH mass calibrations. Ionized [O III] outflows are ubiquitous (78%). One LRD at z=0.196, J1717+3807, shows robust long-term variability in i and WISE bands. The optical-to-NIR continua of LRDs reveal a wide range of temperatures ∼2000−4700 K (peak 0.6−1.4 μm), with a subset showing cooler and larger envelopes than those at high z. Low-z LRDs serve not only as proximate laboratories for probing the nature of LRDs, but also trace the cosmic evolution of this population from the cosmic dawn to the present day.
SN - 2331-8422
ER -