Investigating the Growth of Little Red Dot Descendants at z<4 with the JWST

Abstract

One of JWST's most remarkable discoveries is a population of compact red galaxies known as Little Red Dots (LRDs). Their existence raises many questions about their nature, origin, and evolution. These galaxies show a steep decline in number density-nearly two orders of magnitude-from $z=6$ to $z=3$. In this study, we explore their potential evolution by identifying candidate descendants in CEERS, assuming a single evolutionary path: the development of a blue star-forming outskirt around the red compact core. Our color-magnitude selection identifies galaxies as red as LRDs at $z<4$, surrounded by young, blue stellar outskirts. Morphological parameters were derived from single Sérsic profile fits; physical properties were obtained from SED fitting using a stellar-only model. These "post-LRD" candidates show LRD-like features with $M_{\ast }\sim 10^{10}{M}_{\odot }$, central densities (${\Sigma }_{\ast }\sim 10^{11}{M}_{\odot }{\text{kpc}}^{-2}$ ), compact sizes, and red rest-frame colors, but with an added extended component. Their number density at $z=3\pm 0.5$ ( $\sim 10^{-4.15}{\text{Mpc}}^{-3}$) matches that of LRDs at $5<z<7$ , supporting a possible evolutionary link. We observe a redshift-dependent increase in outskirts mass fraction and galaxy size-from $\sim 250$ pc at $z=5$ to $\sim 600$ pc at $z=3$-suggesting global stellar growth. Meanwhile, the core remains red and compact, but the V-shaped SED fades as the outskirts grow. These findings support an evolutionary scenario in which LRDs gradually acquire an extended stellar component over cosmic time by cold accretion. This may explain the apparent decline in their observed number density at lower redshift.

Accepted for Publication in A&A

References in corpus (39)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• EAZY: A Fast, Public Photometric Redshift Code
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets
• A population of red candidate massive galaxies ~600 Myr after the Big Bang
• NIRCam Performance on JWST In Flight
• JADES. The diverse population of infant Black Holes at 4<z<11: merging, tiny, poor, but mighty
• CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results
• The dramatic size evolution of elliptical galaxies and the quasar feedback
• JWST CEERS & JADES Active Galaxies at z = 4-7 Violate the Local $M_{\bullet }-M_{\star }$ Relation at $>3\sigma$: Implications for Low-Mass Black Holes and Seeding Models
• Star formation sustained by gas accretion
• CEERS Key Paper V: A triality on the nature of HST-dark galaxies
• RUBIES: Evolved Stellar Populations with Extended Formation Histories at $z\sim 7-8$ in Candidate Massive Galaxies Identified with JWST/NIRSpec
• A consistent measure of the merger histories of massive galaxies using close-pair statistics I: Major mergers at $z<3.5$
• EPOCHS VI: The Size and Shape Evolution of Galaxies since z ~ 8 with JWST Observations
• CEERS Key Paper VI: JWST/MIRI Uncovers a Large Population of Obscured AGN at High Redshifts
• A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
• AutoProf -- I. An automated non-parametric light profile pipeline for modern galaxy surveys
• ASTRODEEP-JWST: NIRCam-HST multiband photometry and redshifts for half a million sources in six extragalactic deep fields
• Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1
• Galaxy Size and Mass Build-up in the First 2 Gyrs of Cosmic History from Multi-Wavelength JWST NIRCam Imaging
• JWST CEERS probes the role of stellar mass and morphology in obscuring galaxies
• Exploring the AGN Fraction of a Sample of JWST's Little Red Dots at $5<z<8$: Overmassive Black Holes Are Strongly Favored
• Challenging the AGN scenario for JWST/NIRSpec LRD and non-LRD broad H$\alpha$ emitters in light of non-detection of NIRCam photometric variability and X-ray
• No [CII] or dust detection in two Little Red Dots at z${}_{\mathrm{spec}}$ > 7
• AstroPhot: Fitting Everything Everywhere All at Once in Astronomical Images
• Redshifting galaxies from DESI to JWST CEERS: Correction of biases and uncertainties in quantifying morphology
• JWST/MIRI reveals the true number density of massive galaxies in the early Universe
• Cosmic Outliers: Low-Spin Halos Explain the Abundance, Compactness, and Redshift Evolution of the Little Red Dots
• Lonely Little Red Dots: Challenges to the AGN-nature of little red dots through their clustering and spectral energy distributions
• Active galactic nuclei-heated dust revealed in "little red dots"
• Euclid Quick Data Release (Q1). Extending the quest for little red dots to z<4
• Possible environmental quenching in an interacting little red dot pair at $z\sim 7$
• Where Have All the Little Red Dots Gone? Supermassive Black Hole Binary Dynamics and its Impact on Galaxy Properties
• JWST Reveals Bulge-dominated Star-forming Galaxies at Cosmic Noon
• A weak Ly$\alpha$ halo for an extremely bright Little Red Dot: Indications of enshrouded SMBH growth
• Compact dust-obscured star-formation and the origin of the galaxy bimodality

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• The rise and fall of Little Red Dots could be driven by the environment
• Rapid sinking and efficient mergers of supermassive black holes in compact high-redshift galaxies