The Host Galaxy (If Any) of the Little Red Dots

2024/11/07 by Changhao Chen, Luis C. Ho, Chen, Chang-Hao +5 · 22 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena

paper · pdf · doi:10.48550/arxiv.2411.04446

openalex publication_date 2024/11/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01

Abstract

We investigate the host galaxy properties of eight little red dots (LRDs) selected from the JWST UNCOVER survey, applying a new technique (\tt\string GalfitS) to simultaneously fit the morphology and spectral energy distribution using multi-band NIRCam images covering ∼ 1-4 μ\rm m. We detect the host galaxy in only one LRD, MSAID38108 at z = 4.96, which has a stellar mass of log (M_*/M_\odot) = 8.66^+0.24_-0.23, an effective radius R_e=0.66^+0.08_-0.05 kpc, and a Sérsic index n=0.71^+0.07_-0.08. No host emission centered on the central point source is found in the other seven LRDs. We derive stringent upper limits for the stellar mass of a hypothetical host galaxy by conducting realistic mock simulations that place high-redshift galaxy images under the LRDs. Based on the black hole masses estimated from the broad Hα emission line, the derived stellar mass limits are at least a factor of 10 lower than expected from the z ≈ 0 scaling relation between black hole mass and host galaxy stellar mass. Intriguingly, four of the LRDs (50% of the sample) show extended, off-centered emission, which is particularly prominent in the bluer bands. The asymmetric emission of two sources can be modeled as stellar emission, but the nature of the other two is unclear.

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• A Promise for the JWST era: Massive black holes directly collapsed from wave dark matter haloes, and Star formation in and around their accretion flows
• CAPERS-LRD-z9: A Gas-enshrouded Little Red Dot Hosting a Broad-line Active Galactic Nucleus at z = 9.288
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• The Balmer Break and Optical Continuum of Little Red Dots from Super-Eddington Accretion
• Overmassive Black holes live in compact galaxies in the early Universe
• JWST Insights into Narrow-line Little Red Dots
• Dust Budget Crisis in Little Red Dots
• NEXUS: A Spectroscopic Census of Broad-line AGNs and Little Red Dots at 3\lesssim z\lesssim 6
• The Dichotomy in the Nuclear and Host Galaxy Properties of High-redshift Quasars
• Composite spectrum of Little Red Dot from a standard inner disk and an unstable outer disk

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