---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
PlanS_conform: '1'
_id: '22950'
abstract:
- lang: eng
  text: '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.'
acknowledgement: "The authors thank the anonymous referee for constructive comments,
  which helped improve the manuscript. The authors also thank Xiaohui Fan, Xiaojing
  Lin, Camilla Pacifici, Marianna Annunziatella, Claudia Scarlata, Luis C. Ho, and
  Pablo G. Pérez-González for valuable discussions.\r\n\r\nThis work is based on observations
  made with the NASA/ESA/CSA JWST. The data were obtained from the Mikulski Archive
  for Space Telescopes (MAST) at the Space Telescope Science Institute, which is operated
  by the Association of Universities for Research in Astronomy, Inc., under NASA contract
  NAS 5-03127 for JWST. These observations are associated with JWST programs GTO #1181,
  GTO #1211, GO #1895, GO #3577, and GO #6434 (F. Sun et al. 2025).\r\n\r\nSome of
  the data products presented herein were retrieved from the Dawn JWST Archive (DJA).
  DJA is an initiative of the Cosmic Dawn Center (DAWN), which is funded by the Danish
  National Research Foundation under grant DNRF140.\r\n\r\nThis research has made
  use of data obtained from the Chandra Data Archive provided by the Chandra X-ray
  Center (CXC).\r\n\r\nThe authors acknowledge the FRESCO team led by PI P. Oesch
  for developing their observing program with a zero-exclusive-access period. Processing
  for the JADES NIRCam data release was performed on the lux cluster at the University
  of California, Santa Cruz, funded by NSF MRI grant AST 1828315. Also based on observations
  made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope
  Science Institute, which is operated by the Association of Universities for Research
  in Astronomy, Inc., under NASA contract NAS 526555. The data (G. Illingworth 2015;
  P. Oesch & D. Magee 2023; M. Rieke et al. 2023a; F. Sun & E. Egami 2025) presented
  in this article were obtained from MAST at the Space Telescope Science Institute.\r\n\r\nThe
  authors acknowledge use of the lux supercomputer at UC Santa Cruz, funded by NSF
  MRI grant AST 1828315.\r\n\r\nThe work of G.H.R. and P.R. was also supported by
  grant 80NSSC18K0555, from NASA Goddard Space Flight Center to the University of
  Arizona.\r\n\r\nA.J.B. acknowledges funding from the “FirstGalaxies” Advanced grant
  from the European Research Council (ERC) under the European Union’s Horizon 2020
  research and innovation program (grant agreement No. 789056)\r\n\r\nB.E.R. acknowledges
  support from the NIRCam Science Team contract to the University of Arizona, NAS5-02015,
  and JWST Program 3215.\r\n\r\nThe research of C.C.W. is supported by NOIRLab, which
  is managed by the Association of Universities for Research in Astronomy (AURA) under
  a cooperative agreement with the National Science Foundation.\r\n\r\nS.C. acknowledges
  support by the European Union’s HE ERC Starting grant No. 101040227 - WINGS.\r\n\r\nY.Z.,
  Z.J., B.D.J., C.N.A.W., and P.R. gratefully acknowledge the JWST/NIRCam contract
  to the University of Arizona NAS5-02015.\r\n\r\nS.A. acknowledges support from the
  JWST Mid-Infrared Instrument (MIRI) Science Team Lead, grant 80NSSC18K0555, from
  NASA Goddard Space Flight Center to the University of Arizona.\r\n\r\nR.M., F.D.E.
  acknowledge support by the Science and Technology Facilities Council (STFC), by
  the ERC through Advanced grant 695671 “QUENCH,” and by the UKRI Frontier Research
  grant RISEandFALL. R.M. also acknowledges funding from a research professorship
  from the Royal Society.\r\n\r\nL.B. acknowledges financial support from the Inter-University
  Institute for Data Intensive Astronomy (IDIA), a partnership of the University of
  Cape Town, the University of Pretoria and the University of the Western Cape, and
  from the South African Department of Science and Innovation’s National Research
  Foundation under the ISARP RADIOMAP+ Joint Research Scheme (DSI-NRF grant No. 150551)
  and the CPRR HIPPO Project (DSI-NRF grant No. SRUG22031677). C.J.E.G. acknowledges
  the financial assistance of the South African Radio Astronomy Observatory (SARAO)
  (www.sarao.ac.za)."
article_number: '205'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Pierluigi
  full_name: Rinaldi, Pierluigi
  last_name: Rinaldi
- first_name: George H.
  full_name: Rieke, George H.
  last_name: Rieke
- first_name: Zihao
  full_name: Wu, Zihao
  last_name: Wu
- first_name: Carys J. E.
  full_name: Gilbert, Carys J. E.
  last_name: Gilbert
- first_name: Fabio
  full_name: Pacucci, Fabio
  last_name: Pacucci
- first_name: Luigi
  full_name: Barchiesi, Luigi
  last_name: Barchiesi
- first_name: Stacey
  full_name: Alberts, Stacey
  last_name: Alberts
- first_name: Stefano
  full_name: Carniani, Stefano
  last_name: Carniani
- first_name: Andrew J.
  full_name: Bunker, Andrew J.
  last_name: Bunker
- first_name: Rachana
  full_name: Bhatawdekar, Rachana
  last_name: Bhatawdekar
- first_name: Francesco
  full_name: D’Eugenio, Francesco
  last_name: D’Eugenio
- first_name: Zhiyuan
  full_name: Ji, Zhiyuan
  last_name: Ji
- first_name: Benjamin D.
  full_name: Johnson, Benjamin D.
  last_name: Johnson
- first_name: Kevin
  full_name: Hainline, Kevin
  last_name: Hainline
- first_name: Vasily
  full_name: Kokorev, Vasily
  last_name: Kokorev
- first_name: Nimisha
  full_name: Kumari, Nimisha
  last_name: Kumari
- first_name: Edoardo
  full_name: Iani, Edoardo
  id: 4053390a-6b68-11ef-9828-a3b8adef8d0a
  last_name: Iani
  orcid: 0000-0001-8386-3546
- first_name: Jianwei
  full_name: Lyu, Jianwei
  last_name: Lyu
- first_name: Roberto
  full_name: Maiolino, Roberto
  last_name: Maiolino
- first_name: Eleonora
  full_name: Parlanti, Eleonora
  last_name: Parlanti
- first_name: Brant E.
  full_name: Robertson, Brant E.
  last_name: Robertson
- first_name: Yang
  full_name: Sun, Yang
  last_name: Sun
- first_name: Cristian
  full_name: Vignali, Cristian
  last_name: Vignali
- first_name: Christina C.
  full_name: Williams, Christina C.
  last_name: Williams
- first_name: Christopher N. A.
  full_name: Willmer, Christopher N. A.
  last_name: Willmer
- first_name: Yongda
  full_name: Zhu, Yongda
  last_name: Zhu
citation:
  ama: 'Rinaldi P, Rieke GH, Wu Z, et al. Beyond the dot: An LRD-like nucleus at the
    heart of an IR-bright galaxy and its implications for high-redshift LRDs. <i>The
    Astrophysical Journal</i>. 2026;1006(2). doi:<a href="https://doi.org/10.3847/1538-4357/ae80cd">10.3847/1538-4357/ae80cd</a>'
  apa: 'Rinaldi, P., Rieke, G. H., Wu, Z., Gilbert, C. J. E., Pacucci, F., Barchiesi,
    L., … Zhu, Y. (2026). Beyond the dot: An LRD-like nucleus at the heart of an IR-bright
    galaxy and its implications for high-redshift LRDs. <i>The Astrophysical Journal</i>.
    IOP Publishing. <a href="https://doi.org/10.3847/1538-4357/ae80cd">https://doi.org/10.3847/1538-4357/ae80cd</a>'
  chicago: 'Rinaldi, Pierluigi, George H. Rieke, Zihao Wu, Carys J. E. Gilbert, Fabio
    Pacucci, Luigi Barchiesi, Stacey Alberts, et al. “Beyond the Dot: An LRD-like
    Nucleus at the Heart of an IR-Bright Galaxy and Its Implications for High-Redshift
    LRDs.” <i>The Astrophysical Journal</i>. IOP Publishing, 2026. <a href="https://doi.org/10.3847/1538-4357/ae80cd">https://doi.org/10.3847/1538-4357/ae80cd</a>.'
  ieee: 'P. Rinaldi <i>et al.</i>, “Beyond the dot: An LRD-like nucleus at the heart
    of an IR-bright galaxy and its implications for high-redshift LRDs,” <i>The Astrophysical
    Journal</i>, vol. 1006, no. 2. IOP Publishing, 2026.'
  ista: 'Rinaldi P, Rieke GH, Wu Z, Gilbert CJE, Pacucci F, Barchiesi L, Alberts S,
    Carniani S, Bunker AJ, Bhatawdekar R, D’Eugenio F, Ji Z, Johnson BD, Hainline
    K, Kokorev V, Kumari N, Iani E, Lyu J, Maiolino R, Parlanti E, Robertson BE, Sun
    Y, Vignali C, Williams CC, Willmer CNA, Zhu Y. 2026. Beyond the dot: An LRD-like
    nucleus at the heart of an IR-bright galaxy and its implications for high-redshift
    LRDs. The Astrophysical Journal. 1006(2), 205.'
  mla: 'Rinaldi, Pierluigi, et al. “Beyond the Dot: An LRD-like Nucleus at the Heart
    of an IR-Bright Galaxy and Its Implications for High-Redshift LRDs.” <i>The Astrophysical
    Journal</i>, vol. 1006, no. 2, 205, IOP Publishing, 2026, doi:<a href="https://doi.org/10.3847/1538-4357/ae80cd">10.3847/1538-4357/ae80cd</a>.'
  short: P. Rinaldi, G.H. Rieke, Z. Wu, C.J.E. Gilbert, F. Pacucci, L. Barchiesi,
    S. Alberts, S. Carniani, A.J. Bunker, R. Bhatawdekar, F. D’Eugenio, Z. Ji, B.D.
    Johnson, K. Hainline, V. Kokorev, N. Kumari, E. Iani, J. Lyu, R. Maiolino, E.
    Parlanti, B.E. Robertson, Y. Sun, C. Vignali, C.C. Williams, C.N.A. Willmer, Y.
    Zhu, The Astrophysical Journal 1006 (2026).
das_tickbox: '1'
dataavailabilitystatement: "Facilities: CXO - Chandra X-ray Observatory satellite,
  HST - Hubble Space Telescope satellite, JWST - James Webb Space Telescope.\r\n\r\nSoftware:
  Astropy (Astropy Collaboration et al. 2022), Bagpipes (A. C. Carnall et al. 2019),
  MSAEXP (G. Brammer 2023)NumPy (C. R. Harris et al. 2020), pandas (T. p. d team 2024)Photutils
  (L. Bradley et al. 2016), TOPCAT (M. Taylor 2022), CIAO (A. Fruscione et al. 2006),
  XSpec (K. Arnaud et al. 1999), STPSF (M. D. Perrin et al. 2014)."
date_created: 2026-09-17T11:05:32Z
date_published: 2026-07-29T00:00:00Z
date_updated: 2026-09-22T06:14:37Z
day: '29'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae80cd
external_id:
  arxiv:
  - '2507.17738'
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fulldoi: https://doi.org/10.3847/1538-4357/ae80cd
has_accepted_license: '1'
intvolume: '      1006'
issue: '2'
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
  eissn:
  - 1538-4357
  issn:
  - 0004-637X
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
researchdata_availability: no
scopus_import: '1'
status: public
supplementarymaterial: yes
title: 'Beyond the dot: An LRD-like nucleus at the heart of an IR-bright galaxy and
  its implications for high-redshift LRDs'
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
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type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1006
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