Skip to content
DraconiticResearch
Search Sources API
203,234 studies31 sourcesUpdated 8 min ago
Peer-reviewedCC BYThe Astrophysical Journal

Beyond the Dot: An LRD-like Nucleus at the Heart of an IR-bright Galaxy and its Implications for High-redshift LRDs

  • Pierluigi Rinaldi1
  • George H. Rieke1
  • Zihao Wu2
  • Carys J E Gilbert3
  • Fabio Pacucci2,4
  • L. Barchiesi5,3
  • Stacey L. Alberts6,1
  • Stefano Carniani7
  • Andrew J. Bunker8
  • Rachana Bhatawdekar9
  • Francesco D’Eugenio10
  • Zhiyuan Ji1
14 more authors
  • Benjamin D. Johnson2
  • Kevin Hainline1
  • Vasily Kokorev11
  • Nimisha Kumari6
  • Edoardo Iani12
  • Jianwei Lyu1
  • R. Maiolino13,10
  • Eleonora Parlanti7
  • Brant E. Robertson14
  • Yang Sun1
  • C. Vignali15,16
  • Christina C. Williams17
  • Christopher N. A. Willmer1
  • Yongda Zhu1
17 affiliations
  1. 1University of Arizona
  2. 2Center for Astrophysics∣Harvard & Smithsonian
  3. 3University of Cape Town
  4. 4Harvard University
  5. 5INAF–Istituto di Radioastronomia
  6. 6Space Telescope Science Institute
  7. 7Scuola Normale Superiore
  8. 8University of Oxford
  9. 9European Space Astronomy Centre (ESAC)
  10. 10University of Cambridge
  11. 11The University of Texas at Austin
  12. 12Institute of Science and Technology Austria (ISTA)
  13. 13University College London
  14. 14University of California
  15. 15INAF–Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
  16. 16Università degli Studi di Bologna
  17. 17NSF National Optical-Infrared Astronomy Research Laboratory
Open at sourcePDFDOICite

Abstract

Little red dots (LRDs) are compact, red sources discovered by JWST at high redshift ( z ≳ 4), marked by distinctive “V-shaped” spectral energy distributions (SEDs) and often interpreted as rapidly accreting active galactic nuclei (AGNs). Their true nature remains unclear though, and their evolutionary connection to their lower-redshift counterparts is still poorly constrained. Thus, we present WISEA J123635.56+621424.2 (here dubbed the Saguaro), a z = 2.0145 galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connections to LRDs include the following: (1) its nuclear spectrum shows a clear “V-shaped” SED, and (2) when redshifted to z = 7, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that the Saguaro is not unique by describing similar objects from the literature at z ≲ 3.5. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, (perhaps) AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases.

Related

  1. How bright can a galaxy be? Extreme value predictions for high-redshift survey observables
    Christopher C. Lovell, Theodore Martin, Sandro Tacchella +2
    arXivPreprintCC BY 4.0Full textCosmologyGalaxiesarXiv
  2. The Impact of Inclination, Redshift, and Mass Ratio Selection on Cosmological Constraints from Bright Sirens Beyond Conventional Fisher Approximations
    Gustavo B. F. Lima, Rafael F. Aranha, Rodrigo S. Gonçalves
    arXivPreprintarXiv licenceFull textCosmologyGravitation & general relativityarXiv
  3. Precision kinematic Sunyaev-Zel’dovich measurements across halo mass and redshift with DESI DR2 and ACT DR6. II. Bright galaxy survey and emission-line galaxies
    Boryana Hadzhiyska, Sergio Ferraro, F. J. Qu +50
    Physical review. D/Physical review. D.Peer-reviewedCC BY19 citedCosmologyOpenAlex
  4. A new clump-based star formation model for galaxy simulations: implications for high-redshift compact star clusters
    Shu Horie, Hidenobu Yajima
    arXivPreprintCC BY 4.0Full textGalaxiesarXiv
  5. A Possible High-redshift Origin for the Short GRB 061201: Implications of a Compact Binary Merger beyond Cosmic Noon
    E. Troja, B. O’Connor, Y.-H. Yang +4
    The Astrophysical Journal LettersPeer-reviewedCC BY 4.0Full textHigh-energy astrophysicsCrossref

Cite

BibTeXRIS
BibTeX
@article{rinaldi2026beyond,
  title = {{Beyond the Dot: An LRD-like Nucleus at the Heart of an IR-bright Galaxy and its Implications for High-redshift LRDs}},
  author = {Pierluigi Rinaldi and George H. Rieke and Zihao Wu and Carys J E Gilbert and Fabio Pacucci and L. Barchiesi and Stacey L. Alberts and Stefano Carniani and Andrew J. Bunker and Rachana Bhatawdekar and Francesco D’Eugenio and Zhiyuan Ji and Benjamin D. Johnson and Kevin Hainline and Vasily Kokorev and Nimisha Kumari and Edoardo Iani and Jianwei Lyu and R. Maiolino and Eleonora Parlanti and Brant E. Robertson and Yang Sun and C. Vignali and Christina C. Williams and Christopher N. A. Willmer and Yongda Zhu},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = jul,
  doi = {10.3847/1538-4357/ae80cd},
  url = {https://doi.org/10.3847/1538-4357/ae80cd},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Beyond the Dot: An LRD-like Nucleus at the Heart of an IR-bright Galaxy and its Implications for High-redshift LRDs
AU  - Pierluigi Rinaldi
AU  - George H. Rieke
AU  - Zihao Wu
AU  - Carys J E Gilbert
AU  - Fabio Pacucci
AU  - L. Barchiesi
AU  - Stacey L. Alberts
AU  - Stefano Carniani
AU  - Andrew J. Bunker
AU  - Rachana Bhatawdekar
AU  - Francesco D’Eugenio
AU  - Zhiyuan Ji
AU  - Benjamin D. Johnson
AU  - Kevin Hainline
AU  - Vasily Kokorev
AU  - Nimisha Kumari
AU  - Edoardo Iani
AU  - Jianwei Lyu
AU  - R. Maiolino
AU  - Eleonora Parlanti
AU  - Brant E. Robertson
AU  - Yang Sun
AU  - C. Vignali
AU  - Christina C. Williams
AU  - Christopher N. A. Willmer
AU  - Yongda Zhu
PY  - 2026
DA  - 2026/07/29
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae80cd
UR  - https://doi.org/10.3847/1538-4357/ae80cd
AB  - Little red dots (LRDs) are compact, red sources discovered by JWST at high redshift ( z ≳ 4), marked by distinctive “V-shaped” spectral energy distributions (SEDs) and often interpreted as rapidly accreting active galactic nuclei (AGNs). Their true nature remains unclear though, and their evolutionary connection to their lower-redshift counterparts is still poorly constrained. Thus, we present WISEA J123635.56+621424.2 (here dubbed the Saguaro), a z = 2.0145 galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connections to LRDs include the following: (1) its nuclear spectrum shows a clear “V-shaped” SED, and (2) when redshifted to z = 7, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that the Saguaro is not unique by describing similar objects from the literature at z ≲ 3.5. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, (perhaps) AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases.
SN  - 0004-637X
SN  - 1538-4357
ER  -