654 indexed papers · 430 research notes

Research archive

2025-03-13 · 2503.10958v1

Dot to dot: high-$z$ little red dots in $M_{\rm bh}$-$M_{\rm \star}$ diagrams with galaxy-morphology-specific scaling relations

Alister W. Graham, Igor V. Chilingarian, Dieu D. Nguyen, et al.

Places high‑z little red dots onto morphology‑aware Mbh–M★ diagrams alongside compact stellar systems and local galaxy sequences. With 2023–2024 masses, LRDs are not NSCs (NSCs have higher Mbh/M★); the least‑massive LRDs overlap UCD‑like Mbh and M★, and the full LRD set spans from UCDs to primaeval S0s, while spirals and merger‑built ETGs sit at higher M★. Low‑z AGN align with the quasi‑quadratic/steeper relations defined by local disc galaxies with direct black‑hole masses, emphasizing morphology in coevolution. As 2025 mass updates arrive, placements may shift, potentially bringing LRDs closer to NSCs/UCDs/green‑peas.

LRD overmassive BH demographics high-z

2025-03-07 · 2503.05537v1

Little Red Dots as the Very First Activity of Black Hole Growth

Kohei Inayoshi

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Using 341 Little Red Dots (39 with spectroscopic redshifts) compiled from JWST surveys, this paper models their occurrence across cosmic time. The counts peak at z ~ 6–8 and fall steeply by z < 4, well described by a log‑normal distribution interpreted as the first one or two accretion episodes of newborn seed black holes. Dense circumnuclear gas naturally explains broad Balmer-line absorption, X‑ray weakness, and brief super‑Eddington bursts that yield overmassive BHs relative to local relations. Summing recurrent episodes reproduces the global AGN abundance evolution ∝ (1+z)^(−5/2) and provides an analytic form for the LRD redshift dependence for future tests.

LRD BH seeds super-Eddington overmassive BH demographics high-z

2025-03-05 · 2503.03870v1

The Convergence of Heavy and Light Seeds to Overmassive Black Holes at Cosmic Dawn

Haojie Hu, Kohei Inayoshi, Zoltan Haiman, et al.

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A semi-analytic growth model tied to dark-matter halo assembly follows M_BH/M_star for both heavy and light seeds under feedback-limited, episodic super-Eddington accretion. Despite mass loss in winds, the ratio first increases and then converges to a universal ~0.1–0.3 set by the balance between nuclear gas feeding and star-formation efficiency, forming an attractor in the M_BH–M_star plane. On this attractor, overmassive BHs grow more slowly than their hosts while undermassive seeds catch up rapidly, erasing seed-memory by z~4–6. The model predicts that 10^5–10^6 Msun BHs at higher redshift that deviate from this trend would reveal their birth conditions.

overmassive BH BH seeds super-Eddington simulation high-z

2025-01-22 · 2501.13082v1

BlackTHUNDER -- A non-stellar Balmer break in a black hole-dominated little red dot at $z=7.04$

Xihan Ji, Roberto Maiolino, Hannah Übler, et al.

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BlackTHUNDER analyzes JWST NIRSpec-IFU plus archival MSA data of the triply imaged lensed LRD Abell2744-QSO1 at z=7.04, confirming a smooth Balmer break and a broad Hβ from the BLR. The narrow Hβ dispersion gives M_dyn < 4×10^8 Msun, capping the stellar contribution to <10% of the optical continuum and favoring a non-stellar Balmer break produced by an AGN continuum filtered by very dense (n_H ~ 10^10 cm^-3), nearly dust-free gas likely in/around the BLR; a tentative 3σ Hβ absorption appears in the R2700 spectrum. The black hole is overmassive relative to both stellar and dynamical masses, with hints of variability and an initial reverberation-mapping attempt. This picture alleviates the extreme stellar-density problem for LRDs and may generalize to similar V-shaped continua.

LRD v-shaped SED broad Balmer overmassive BH spectroscopy high-z