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Abstract Little Red Dots (LRDs), among the most enigmatic high-redshift discoveries by JWST, are commonly believed to be powered by accreting supermassive black holes. Here, we explore the possibility that these sources are globular clusters in formation, with rest-frame UV arising from a very young stellar population and rest-frame optical from a short-lived supermassive (>10⁴ M_⊙) star. The spectral profiles of LRDs are broadly consistent with this scenario, though the observed temperatures and bolometric luminosities favor emission reprocessed by optically thick continuum-driven winds not fully captured by current models. The LRDz ∼ 5−7 UV luminosity function naturally evolves, under standard evolutionary and mass-loss prescriptions, into a present-day mass function with a turnover at ${\log }_{10}($ M_*/M_⊙) = 5.3 and an exponential cutoff at high masses, consistent with local globular cluster populations. We estimate the total present-day number density of LRDs formed across all redshifts to be ≈0.3 Mpc⁻³, similar within uncertainties to local globular clusters. The observed LRD redshift range matches the age distribution of metal-poor globular clusters, without current LRD counterparts to the metal-rich population. If LRDs are globular clusters in formation, we predict chemical abundance patterns characteristic of multiple stellar populations, including enhanced He and N, and potential Na–O and Al–Mg anticorrelations. These results offer a local perspective to explore this surprisingly abundant population of distant sources, and a potential new window into extreme stellar astrophysics in the early Universe. 

We used the ultra-deep GLIMPSE JWST/NIRCam survey to constrain the faint end of the [O III]+Hβluminosity function (LF) down to 10³⁹erg s⁻¹atz ∼ 7 − 9 behind the lensed Hubble Frontier Field galaxy cluster Abell S1063. We applied a spectral energy distribution fitting on a Lyman-break galaxy selected sample of 164 lensed galaxies and measured their combined Hβ+[O III]λλ4960, 5008 flux to build the emission line LF. We found a [O III]+HβLF with a faint-end slope (α= −1.78^+0.06_−0.06forz = 7 − 8 andα= −1.55^+0.11_−0.11forz = 8 − 9), which is flatter than the UV LF at similar redshifts (α ≤ −2) and suggests a lower number density of weak [O III]+Hβemitting galaxies at fixedM_UV. We analysed several possible explanations: (i) a decrease in the [O III]+Hβ-to-UV ratio due to bursty star formation histories (SFHs), (ii) the effect of metallicity on the [O III]-to-Hβratio, or (iii) signs of a faint-end turnover in the UV LF. Under the assumption of an evolving [O III]-to-Hβratio, we separated the contribution of [O III]λ5008 and Hβand obtained a flatter [O III]λ5008 LF (α= −1.66^+0.05_−0.05forz = 7 − 8 andα= −1.45^+0.09_−0.10forz = 8 − 9) but steeper HβLF ($$ \alpha=-1.95_{-0.08}^{+0.08} $$ forz = 7 − 8 andα= −1.68^+0.13_−0.14forz = 8 − 9). The combination of a decreasing metallicity and bursty SFH can reconcile the observed differences between the UV and [O III]+HβLF. By converting this LF into the ionising photon-production rateṄ_ion, we show that galaxies withL_Hα ≥ 10³⁹erg s⁻¹, that is, with a star formation rate (SFR) (Hα)  ≥  5 × 10⁻³M_⊙yr⁻¹) cause 31%−90% and 46%−156% of the ionising photon budget (at 7 < z < 8 and 8 < z < 9), when we assume a constant escape fraction of Lyman-continuum photon (f_esc = 0.14). The shape of the LF further shows the negligible contribution of faint galaxies to theṄ_ion. Additionally, we derived the cosmic star formation rate density (SFRD), finding results consistent with previous estimates. However, the sensitivity of GLIMPSE to lower SFRs reinforces the conclusion that very faint galaxies contribute very little toṄ_ionand the SFRD. Our results suggests that GLIMPSE has detected the bulk of the total [O III]+Hβemission from star-forming galaxies, and that galaxies below our detection limits are likely minor contributors to cosmic re-ionisation. 

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 We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10%Z_⊙), lensed, compact (R_eff ∼ 20 pc) galaxy RXCJ2248 atz= 6.1, revealed by unprecedentedly deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and broad Balmer and [Oiii] components (FWHM ∼700–3000 km s⁻¹). We detect broadened Heiiλ1640 andλ4687 (FWHM ∼ 530 km s⁻¹) and strong Niiiλ4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed Wolf Rayet (WR) features to date. We measure the multiphase nebular density across five ions, the direct-method metallicity ( $12+\log (\mathrm{O}/\mathrm{H})=7.753\pm 0.025$ ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( $\log (\mathrm{N}/\mathrm{O})=-0.391\pm 0.037$ from N⁺, N⁺², and N⁺³) but suppressed C/O relative to empirical C/N trends. We show that this abundance pattern can be explained by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback but before dilution by later yields (e.g., supernovae). The observed frequency of strong N emitters at high−zimplies a ∼50 Myr burst duty cycle, suggesting that N/O outliers may represent a brief but ubiquitous phase in the evolution of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the first direct evidence of WR-driven nitrogen enrichment in the first billion years of the Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn. 

Abstract As observations have yet to constrain the ionizing properties of the faintest (M_UV≳ −16) galaxies, their contribution to cosmic reionization remains unclear. The rest-frame ultraviolet (UV) continuum slope (β) is a powerful diagnostic of stellar populations and one of the few feasible indicators of the escape fraction of ionizing photons (f_esc) for such faint galaxies at high redshift. Leveraging ultradeep JWST/NIRCam GLIMPSE imaging of the strong lensing field Abell S1063, we estimate the UV continuum slopes of 553 galaxies atz> 6 with absolute magnitudes down toM_UV≃ −12.5. We find a modest evolution ofβwith redshift and a flattening in theβ–M_UVrelation such that galaxies fainter thanM_UV∼ −16.5 no longer exhibit the bluest UV slopes. The 136 ultrafaint galaxies withM_UV> −16 are a diverse population encompassing dusty (30%), old (15%), and low-mass (50%) galaxies. We apply the empiricalβ–f_escrelation from local Lyman continuum leakers, finding the meanf_escpeaks at ∼20% atM_UV= −16.5 and declines towards fainter galaxies, while remaining consistent withf_esc= 14% within the uncertainties, in agreement with recent radiative transfer simulations. Incorporating GLIMPSE constraints on the UV luminosity function, ionizing photon production efficiency, and escape fractions produces a reionization history consistent with independent observational constraints. Our results indicate galaxies with anM_UVbetween −18 and −14 supplied ∼60% of the ionizing photons to cosmic reionization, while the lowerf_escof fainter galaxies produces a natural cutoff in the ionizing photon production rate density. 

ABSTRACT Using ultra-deep James Webb Space Telescope (JWST)/NIRCam imaging from the GLIMPSE survey, enhanced by gravitational lensing from the Abell S1063 cluster, we investigate the faintest galaxies ever observed at redshifts $$z\sim 9{\text{-}}15$$. We identify 105 galaxy candidates spanning absolute ultraviolet (UV) magnitudes $$M_{\mathrm{UV}}$$\sim -18$$ to $-13$, about 3 mag fainter, on average, than prior JWST studies. We place strong constraints on the ultra-faint end of the UV luminosity function (UVLF), finding minimal evolution in the faint-end slope, from $$\alpha =-2.01\pm 0.20$$ at $z=9$ to $$\alpha =-2.10\pm 0.19$$ at $z=13$, in contrast to the rapid evolution observed at $$z\sim 0{\text{-}}9$$. Integrating the UVLF down to $$M_{\mathrm{UV}}$$=-16$, we find the cosmic star formation rate density, $$\rho _{\rm SFR}$$, evolves as $$\propto (1+z)^{-2.94^{+0.06}_{-0.10}}$$, over $$z=9{\text{-}}13$$, which is significantly shallower than most theoretical predictions. Extending the integration limit to $$M_{\mathrm{UV}}$$=-13$ reveals galaxies fainter than $$M_{\mathrm{UV}}$$=-16$ contribute over 50 per cent of the total cosmic star formation rate density at $$z\sim 12$$. This excess may indicate enhanced star formation efficiency during the earliest phases of galaxy formation. Alternatively, it could arise from bursty star formation histories; minimal dust attenuation; or an evolving initial mass function. However, existing models incorporating these effects fail to fully reproduce the observed redshift evolution of $$\rho _{\rm SFR}$$. We note that low-redshift contamination and cosmic variance may affect our results, as the limited survey volume may not be representative of the broader galaxy population. Similar observations and spectroscopic confirmation are required to validate these findings. 

Abstract Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and carefully validate it through completeness and contamination simulations. We systematically search ≃ 500 arcmin²across JWST legacy fields for Pop III candidates, including GLIMPSE, which, assisted by gravitational lensing, has produced JWST’s deepest NIRCam imaging thus far. We discover one promising Pop III galaxy candidate (GLIMPSE-16043) at $z=6.50_{-0.24}^{+0.03}$ , a moderately lensed galaxy ( $\mu =2.9_{-0.2}^{+0.1}$ ) with an intrinsic UV magnitude of $M_{\mathrm{UV}}=-15.89_{-0.14}^{+0.12}$ . It exhibits key Pop III features: strong Hαemission (rest-frame EW 2810 ± 550 Å); a Balmer jump; no dust (UV slopeβ = −2.34 ± 0.36); and undetectable metal lines (e.g., [Oiii]; [Oiii]/Hβ < 0.44), implying a gas-phase metallicity ofZ_gas/Z_⊙ < 0.5%. These properties indicate the presence of a nascent, metal-deficient young stellar population (<5 Myr) with a stellar mass of ≃10⁵M_⊙. Intriguingly, this source deviates significantly from the extrapolated UV–metallicity relation derived from recent JWST observations atz= 4–10, consistent with UV enhancement by a top-heavy Pop III initial mass function or the presence of an extremely metal-poor active galactic nucleus. We also derive the first observational constraints on the Pop III UV luminosity function atz ≃ 6–7. The volume density of GLIMPSE-16043 (≈10⁻⁴cMpc⁻³) is in excellent agreement with theoretical predictions, independently reinforcing its plausibility. This study demonstrates the power of our novel NIRCam method to finally reveal distant galaxies even more pristine than the Milky Way’s most metal-poor satellites, thereby promising to bring us closer to the first generation of stars than we have ever been before. 

Abstract SN H0pe is a triply imaged supernova (SN) at redshiftz= 1.78 discovered using the James Webb Space Telescope. In order to classify the SN spectroscopically and measure the relative time delays of its three images (designated A, B, and C), we acquired NIRSpec follow-up spectroscopy spanning 0.6–5μm. From the high signal-to-noise spectra of the two bright images B and C, we first classify the SN, whose spectra most closely match those of SN 1994D and SN 2013dy, as a Type Ia SN. We identify prominent blueshifted absorption features corresponding to Siiiλ6355 and CaiiHλ3970 and Kλ3935. We next measure the absolute phases of the three images from our spectra, which allow us to constrain their relative time delays. The absolute phases of the three images, determined by fitting the three spectra to Hsiao07 SN templates, are ${6.5}_{-1.8}^{+2.4}$ days, ${24.3}_{-3.9}^{+3.9}$ days, and ${50.6}_{-15.3}^{+16.1}$ days for the brightest to faintest images. These correspond to relative time delays between Image A and Image B and between Image B and Image C of $-{122.3}_{-43.8}^{+43.7}$ days and ${49.3}_{-14.7}^{+12.2}$ days, respectively. The SALT3-NIR model yields phases and time delays consistent with these values. After unblinding, we additionally explored the effect of using Hsiao07 template spectra for simulations through 80 days instead of 60 days past maximum, and found a small (11.5 and 1.0 days, respectively) yet statistically insignificant (∼0.25σand ∼0.1σ) effect on the inferred image delays. 

Strong gravitational magnification enables the detection of faint background sources and allows researchers to resolve their internal structures and even identify individual stars in distant galaxies. Highly magnified individual stars are useful in various applications, including studies of stellar populations in distant galaxies and constraining dark matter structures in the lensing plane. However, these applications have been hampered by the small number of individual stars observed, as typically one or a few stars are identified from each distant galaxy. Here, we report the discovery of more than 40 microlensed stars in a single galaxy behind Abell 370 at redshift of 0.725 (dubbed ‘the Dragon arc’) when the Universe was half of its current age, using James Webb Space Telescope observations with the time-domain technique. These events were found near the expected lensing critical curves, suggesting that these are magnified stars that appear as transients from intracluster stellar microlenses. Through multi-wavelength photometry, we constrained their stellar types and found that many of them are consistent with red giants or supergiants magnified by factors of hundreds. This finding reveals a high occurrence of microlensing events in the Dragon arc and demonstrates that time-domain observations by the James Webb Space Telescope could lead to the possibility of conducting statistical studies of high-redshift stars.