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Abstract The detection of strong Balmer breaks and absorption features in Little Red Dots (LRDs) suggests they host active galactic nuclei embedded within dense gas envelopes, potentially powered by super-Eddington accretion. We present GLIMPSE-17775, a luminous (L_bol ∼ 10⁴⁵erg s⁻¹) LRD atz= 3.501 behind Abell S1063 (μ ∼ 2), observed with deep JWST/NIRCam and a ∼20 hr (80 hr delensed) NIRSpec G395M spectrum. The data reveal over 40 emission and absorption features, including a rich forest of low-ionization Feiilines and numerous broad hydrogen recombination transitions. We use this depth to test the dense-gas interpretation through five independent diagnostics. Nearly all permitted lines show exponential wings with consistent FWHM, a signature of Thomson scattering requiringn_e ≳ 10⁸cm⁻³. Adopting this width yieldsM_BH ∼ 10^6.7M_⊙, a factor of 10 lower than Gaussian fits, andλ_Edd ∼ 1.8. Additional diagnostics support the same picture: a pronounced Balmer break (f_ν,4050/f_ν,3670 = 2.0 ± 0.1), enhanced Heiλ7065 andλ10830 with P-Cygni absorption, Bowen-fluorescent Oiλ8446–λ11290 emission requiring Lyβpumping, and 16 Feiilines matching fluorescence models. These features indicate a dense (n ∼ 10⁸cm⁻³), partially ionized cocoon where scattering and fluorescence dominate line formation, providing strong evidence that at least some LRDs are powered by super-Eddington black hole growth in the early Universe. 

Abstract Early JWST photometric studies discovered a population of UV-faint ( $<{\mathit{L}}_{\mathrm{UV}}^{*}$ )z ∼ 6.5–8 Lyman break galaxies with spectral energy distributions implying young ages (∼10 Myr) yet relatively weak Hβ+ [Oiii] equivalent widths (EW_{Hβ+ [Oiii]} ≈ 400 Å). These galaxies seemingly contradict the implicit understanding that young star-forming galaxies are ubiquitously strong Hβ+ [Oiii] emitters, i.e., extreme emission line galaxies (EW ≳750 Å). Low metallicities, high Lyman continuum escape fractions, and rapidly declining star formation histories have been proposed as primary drivers behind low Hβ+ [Oiii] EWs, but the blend of Hβ+ [Oiii] in photometric studies makes proving one of these scenarios difficult. We aim to characterize this peculiar population with deep spectroscopy from the JWST Advanced Deep Extragalactic Survey. We find that a significant subset of these galaxies atz ≳ 2 with modest Hβ+ [Oiii] EWs (≈300–600 Å) have high ionization efficiencies ( $\log {\xi }_{\mathrm{ion}}\gtrsim 25.5\mathrm{Hz}{\mathrm{erg}}^{-1}$ ). Suppressed [Oiii] EW values yet elevated Hαand HβEW values imply that the level of chemical enrichment is the primary culprit, supported by spectroscopic measurements of metallicities below 12 + log(O/H) ≈ 7.70 (0.1Z_⊙). We demonstrate that integrated Hβ+ [Oiii] selections (e.g., Hβ+ [Oiii] EW > 700 Å) exclude the most metal-poor efficient ionizers and favor (1) more chemically enriched systems with comparable extreme radiation fields and (2) older starbursting systems. In contrast, metallicity degeneracies are reduced in Hαspace, enabling the identification of these metal-poor efficient ionizers by their specific star formation rate. 

Abstract We study the large-scale environments and clustering properties of 28 low-luminosity active galactic nuclei (AGNs) atz = 3.9–6 in the GOODS-N field. Our sample, identified from the JWST NIRCam Imaging and WFSS data in Complete NIRCam Grism Redshift Survey and First Reionization Epoch Spectroscopically Complete Observations surveys with either broad Hαemission lines or V-shaped continua, are compared to 782 Hαemitters (HAEs) selected from the same data. These AGNs are located in diverse large-scale environments and do not preferentially reside in denser environments compared to HAEs. Their overdensity field,δ, averaged over (15h⁻¹cMpc)³, ranges from −0.56 to 10.56, and shows no clear correlation with broad-line luminosity, black hole (BH) masses, or the AGN fraction. It suggests that >10 cMpc structures do not significantly influence BH growth. We measure the two-point cross-correlation function of AGNs with HAEs, finding a comparable amplitude to that of the HAE autocorrelation. This indicates similar bias parameters and host dark matter halo masses for AGNs and HAEs. The correlation length of field AGNs is 4.26h⁻¹cMpc and 7.66h⁻¹cMpc at 3.9 < z < 5 and 5 < z < 6, respectively. We infer a median host dark matter halo mass of $\log (M_h/M_{\odot })\approx 11.0-11.2$ and host stellar masses of $\log \left(M_{\star }/M_{\odot }\right)\approx 8.4\text{–}8.6$ by comparing with the UniverseMachinesimulation. Our clustering analysis suggests that low-luminosity AGNs at high redshift reside in normal star-forming galaxies with overmassive BHs. They represent an intrinsically distinct population from luminous quasars and could be a common phase in galaxy evolution. 

Abstract We study the luminosity function (LF) and clustering properties of 888 Hαemitters (HAEs) at 3.75 < z < 6 in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans ∼62 arcmin²and reachesL_Hα ∼ 10^41.2erg s⁻¹. We identify two prominent filamentary protoclusters atz ≈ 4.41 andz ≈ 5.19, hosting 98 and 144 HAEs, respectively. The observed HαLFs show similar shallow faint-end slopes for both protocluster and field galaxies at 3.75 < z < 5, and for the protocluster at 5 < z < 6 (α ≈ −1.2 to −1.3). In contrast, the field LF at 5 < z < 6 has a much steeper slope ( $\alpha =-1.87_{-0.23}^{+0.30}$ ), suggesting that protocluster galaxies atz > 5 are more evolved, resembling the populations at 3.75 < z < 5. The observed star formation rate density from Hαintegrated down to 0.45M_⊙yr⁻¹, is $0.050_{-0.003}^{+0.002}{M}_{\odot }{\mathrm{yr}}^{-1}{\mathrm{Mpc}}^{-3}$ at 3.75 < z < 5 and $0.046_{-0.004}^{+0.006}{M}_{\odot }{\mathrm{yr}}^{-1}{\mathrm{Mpc}}^{-3}$ at 5 < z < 6, with protoclusters contributing about 25% and 55%, respectively. This implies a large fraction of star formation atz> 4 occurs in protoclusters. For the first time, we conduct the star formation-rate-limited three-dimensional clustering analysis atz > 4. We find that the filamentary geometry of protoclusters flattens the power-law shape of the HAE autocorrelation functions, with slopes much shallower than the typically assumed value. The autocorrelation function of field HAEs has a correlation length of $r_0=4.61_{-0.68}^{+1.00}{h}^{-1}\mathrm{Mpc}$ atz ≈ 4−5 and $r_0=6.23_{-1.13}^{+1.68}{h}^{-1}\mathrm{Mpc}$ atz ≈ 5−6. Comparing the observed correlation functions with the UniverseMachinesimulation, we infer the dark matter (sub-)halo masses of HAEs to be $\log (M_h/M_{\odot })=11.0-11.2$ atz ≈ 4−6, with a scatter of 0.4 dex.