Saved in:
| Main Authors: | , , , , , , , , , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2026
|
| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.21574 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866911703337271296 |
|---|---|
| author | Lin, Xiaojing Fan, Xiaohui Cai, Zheng Liu, Yichen Sun, Fengwu Bian, Fuyan Li, Mingyu Mao, Junjie Greene, Jenny E. Liu, Hanpu Li, Jiaxuan Liu, Weizhe Ma, Yilun Sun, Zechang Zhang, Zijian |
| author_facet | Lin, Xiaojing Fan, Xiaohui Cai, Zheng Liu, Yichen Sun, Fengwu Bian, Fuyan Li, Mingyu Mao, Junjie Greene, Jenny E. Liu, Hanpu Li, Jiaxuan Liu, Weizhe Ma, Yilun Sun, Zechang Zhang, Zijian |
| contents | 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 $7.5 \times 10^{-10}$ cMpc$^{-3}$. We conducted near-IR spectroscopic follow-up observations for 18 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 H$α$/H$β\sim 16$), frequent Balmer absorption (67%), 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 $\sim 2000-4700$ K (peak $0.6-1.5$ $μ$m), 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_21574 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | (LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample Lin, Xiaojing Fan, Xiaohui Cai, Zheng Liu, Yichen Sun, Fengwu Bian, Fuyan Li, Mingyu Mao, Junjie Greene, Jenny E. Liu, Hanpu Li, Jiaxuan Liu, Weizhe Ma, Yilun Sun, Zechang Zhang, Zijian Astrophysics of Galaxies 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 $7.5 \times 10^{-10}$ cMpc$^{-3}$. We conducted near-IR spectroscopic follow-up observations for 18 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 H$α$/H$β\sim 16$), frequent Balmer absorption (67%), 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 $\sim 2000-4700$ K (peak $0.6-1.5$ $μ$m), 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. |
| title | (LRDs)$^2$: The Low-ReDshift Little Red Dots Survey. II. DESI DR1 Sample |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2605.21574 |