Metallicity is a crucial tracer of galaxy evolution, providing insights into gas accretion, star formation, and feedback. At high redshift, these processes reveal how early galaxies assembled and enriched their interstellar medium. In this work, we present rest-frame optical spectroscopy of 12 massive (log(M-*/M-circle dot)>9) galaxies at z similar to 6-8 from the REBELS ALMA large program, observed with JWST NIRSpec/IFU in the prism mode. These observations span emission lines from [O II]lambda 3727,9 to [S II]lambda 6716,31, providing key information on nebular dust attenuation, ionisation states, and chemical abundances. We find lower O32 ratios (average similar to 3.7) and [OIII]lambda 5007 equivalent widths (median EW[OIII] similar to 480 angstrom) than are generally found in existing large spectroscopic surveys at z > 6, indicating less extreme ionising conditions. Strong-line diagnostics suggest that these systems are some of the most metal-rich galaxies observed at z > 6 (average Z(gas) similar to 0.4Z(circle dot)), including sources with near-solar oxygen abundances, in line with their high stellar masses (average logM(*)/M-circle dot similar to 9.5). Supplementing with literature sources at lower masses, we investigate the mass-metallicity and fundamental metallicity relations (MZR and FMR, respectively) over a 4 dex stellar mass range at 6 < z < 8. In contrast to recent studies of lower-mass galaxies, we find no evidence for negative offsets to the z = 0 FMR for the REBELS galaxies. This work demonstrates the existence of chemically-enriched galaxies just similar to 1 Gyr after the Big Bang, and indicates that the MZR is already in place at these early times, in agreement with other recent z > 3 studies.

We present results of new observations of [O i] 145 mu m and [N ii] 205 mu m emission lines from four star-forming galaxies at redshifts between z = 6.58 and 7.68 that have previous detections of [C ii] 158 mu m and dust continua. Using the Atacama Large Millimeter/submillimeter Array, we successfully detect [O i] 145 mu m emission from all targets at >4 sigma significance. However, [N ii] 205 mu m emission is undetected in all galaxies (signal-to-noise ratio < 3.5 sigma) except for a tentative detection from A1689-zD1. From the observed high [C ii]/[N ii] emission line ratios (greater than or similar to 20-80), we find that most of the [C ii] 158 mu m emission arises from neutral gas regions (3 sigma lower limits of greater than or similar to 74%-96%). From [O i] 145 mu m, [C ii] 158 mu m lines, and IR luminosities, we estimate the neutral gas densities of n(H) = 10(3.5)-10(6) cm(-3) and the far-UV (FUV) radiation strengths of G(0) similar to 10(2.5)-10(3). While the neutral gas densities are similar to those of high-redshift starburst galaxies, the FUV strengths are lower compared to both local and high-redshift starbursts. Finally, we estimate atomic hydrogen masses using [O i] 145 mu m emission lines and the oxygen abundances measured from recent JWST observations. We find gas mass ratios of f(gas) similar to 0.3-0.8, which are similar to earlier studies using [C ii] 158 mu m. Starting from this pilot observation, future large [O i] 145 mu m emission line surveys will provide us with currently little-known neutral gas properties of star-forming galaxies in the early Universe.

Ly alpha spectroscopy with JWST is opening a new window on the sizes of ionized bubbles through the reionization epoch. Theoretical expectations suggest typical bubble radii should be 0.6-1.5 pMpc at z similar or equal to 7, assuming neutral hydrogen fractions of the intergalactic medium in the range = 0.5-0.7. Here, we investigate this picture using JWST to characterize the environment and Ly alpha emission of 292 galaxies at 7.0 < z < 8.5 across five fields spanning a comoving volume of 1.3 & times; 10(6) Mpc(3). If the reionization predictions are correct, we should see overdensities and strong Ly alpha emission clustered in redshift windows of dz = 0.04-0.08 and angular scales of 5 '-11 '. We detect Ly alpha emission in 36 out of 292 galaxies, including nine new Ly alpha detections, two of which (in the UltraDeep Survey field) show extremely large equivalent widths (EW = 200(-78)(+50) & Aring; and 284(-75)(+56) & Aring;). We identify 13 significant (4-11 & times;) galaxy overdensities using redshifts from NIRCam grism and NIRSpec. Strong Ly alpha emitters are almost uniformly found in the overdensities, with nearly all located between the center and back of the structures. The overdensities that host the strong Ly alpha emitters span typical line-of-sight distances (dz similar to 0.14) and angular scales (similar to 8 ') that are comparable to the predicted bubble sizes at z similar or equal to 7. We discuss evidence that the Extended Groth Strip is mostly ionized along a 24 pMpc sight line at z similar or equal to 7.0-7.6, based on the presence of three overdense structures and 10 Ly alpha emitters in this volume, and find such a large ionized region would pose tension with standard reionization models.

JWST has revealed a population of super-luminous early galaxies with a volume density in excess of most expectations. The spectra reveal diverse properties: while some reveal strong emission lines characteristic of galaxies in the midst of strong bursts, others show weak emission lines that could reflect old stellar populations, large escape fractions, or post-burst star formation histories. Through the JWST Cycle 4 large program SPURS, we have obtained ultra-deep (29 hr) rest-frame UV spectroscopy of a z=9.3 super-luminous (M_ UV=-21.66) galaxy with large assembled stellar mass (1.6×10^9 M_⊙) and extremely weak emission lines (Hβ EW ≈25 Å). The strong stellar wind features and rest-optical line ratios suggest the galaxy is already significantly enriched, with a metallicity of 0.4–0.7 Z_⊙. The interstellar absorption lines reveal outflows (v≃ -161 km s^-1) with a large neutral gas covering fraction, suggesting that the weak emission lines are not due to large escape fractions. The combination of the Balmer break, weak emission lines, and stellar wind features constrains the star formation history, indicating a recent burst of star formation lasting 10–20 Myr followed by a downturn over the last 10 Myr. The observations suggest that z≳ 9 weak emission line galaxies such as this source can be explained by stochastic star formation, provided that the downturns in star formation are recent (i.e., <10 Myr prior to observation). The ultra-deep grating spectrum enables the IGM damping wing to be characterized, decoupling the effects of local absorption. The smooth Lyα break indicates that this source, one of the most massive galaxies known at z>9, is likely situated in a small ionized bubble (0.29_-0.09^+0.11 pMpc), as is common at large neutral hydrogen fractions (x̅_ HI=0.81_-0.21^+0.14).

Context. JWST provides a unique dataset for studying the earliest stages of reionisation at z > 9, promising insights into the first galaxies. Many JWST/NIRSpec prism spectra of z > 5 galaxies have revealed smooth Lyman-alpha breaks, implying damping wing scattering by neutral hydrogen. Aims. We investigate what current prism spectra imply about the intergalactic medium (IGM) at z > 6 and how best to use NIRSpec spectra to recover IGM properties. We use a sample of 99 z ∼ 5.5 − 13 galaxies with high S/N prism spectra in the public archive, including 12 at z > 10. Methods. We analyse these spectra using damping wing sightlines from inhomogeneous reionising IGM simulations, mapping between the distance of a source from the neutral IGM and the average IGM neutral fraction. We marginalise over absorption by local neutral hydrogen around the galaxies and Lyman-alpha emission. Results. We observe a decline in the median and variance of flux around the Ly α break with increasing redshift, consistent with an increasingly neutral IGM, as ionized regions become smaller and rarer. At z ≳ 9 the spectra become consistent with an almost fully neutral IGM. We find S/N > 15 per pixel is required to robustly estimate IGM properties from prism spectra. We fit a sub-sample of high S/N spectra and infer mean IGM neutral fractions of x̄ H I = 0.33 −0.27 +0.18 , 0.64 −0.23 +0.17 (> 0.70 excluding GNz11) at z ≈ 6.5, 9.3. We also investigate local HI absorption, finding a median column density of log 10 N H I ≈ 10 20.8 cm −2 , comparable to z ∼ 3 Lyman-break galaxies, with no significant redshift evolution z ≳ 5.5. We find galaxies showing the highest column density absorption are more likely to be in close associations of sources (≲500 pkpc), implying absorption is enhanced in massive dark matter halos. Future deep prism and grating spectroscopy of z > 9 sources will provide tighter constraints on the earliest stages of reionisation, key for understanding the onset of star formation.

We present detections of auroral emission lines of [O iii], [O ii], [S iii], and [S ii] in deep JWST/NIRSpec spectroscopy for 41 star-forming galaxies at z = 1.4-7.2 from the AURORA survey. We combine these new observations with 98 star-forming galaxies at z = 1.3-10.6 with detected auroral lines drawn from the literature to form a sample of 139 high-redshift galaxies with robust electron temperature and direct-method oxygen abundance determinations. This sample notably covers a wider dynamic range in metallicity than previous work, spanning 0.02-0.9 Z circle dot. We calibrate empirical relations between 19 emission-line ratios and oxygen abundance, providing a robust tool set to infer accurate gas-phase metallicities of high-redshift galaxies when auroral lines are not detected. While calibrations based on lines of alpha elements (O, Ne, S, Ar) appear reliable, we find significant scatter in calibrations involving lines of N driven by a high dispersion in N/O at fixed O/H, suggesting that N-based line ratios are less reliable tracers of the oxygen abundance at high redshift. These new high-redshift calibrations are notably offset from those based on typical z similar to 0 galaxy and H ii region samples, and are better matched by samples of extreme local galaxies that are analogs of high-redshift sources. The new metallicity calibrations presented in this work pave the way for robust studies of galaxy chemical evolution in the early Universe, leading to a better understanding of baryon cycling and galaxy formation from Cosmic Noon through the Epoch of Reionization.

Accurate chemical compositions of star-forming regions provide a critical diagnostic tool for characterizing the star formation history and gas flows that regulate galaxy formation. However, the abundance discrepancy factor (ADF) between measurements derived from the "direct" optical electron temperature (Te) method and those from recombination lines (RLs) introduces a similar to 0.2 dex systematic uncertainty in the oxygen abundance. The degree of uncertainty for other elements is unknown. We conduct a comprehensive analysis of O++ and N+ ion abundances using optical and far-infrared (far-IR) spectra of a star-forming region within the nearby dwarf galaxy Haro 3, which exhibits a typical ADF. Assuming homogeneous conditions, the far-IR emission indicates an oxygen abundance higher than that derived using the Te method and consistent with the RL value, as expected from temperature fluctuations, whereas the far-IR nitrogen abundance is too large to be explained by temperature fluctuations. A two-phase analytical model reveals that differential dust obscuration associated with temperature inhomogeneity is likely required to explain all the emission-line ratios, and that the total oxygen metallicity of two phases is consistent with the RL metallicity. Our findings underscore the critical importance of resolving the cause of abundance discrepancies and understanding the biases between different metallicity methods. This work presents a promising methodology, and we identify further approaches to address the dominant sources of uncertainty.

We provide a review of our current knowledge of galaxies throughout the first billion years of cosmic history. This field has undergone a transformation in the last two years following the launch of JWST, and we aim to deliver an observational overview of what we have learned about z≳ 5 galaxies. We introduce the latest selection methods of high redshift galaxies and describe new measurements of the census of continuum-selected and dusty star forming galaxies at z≳ 5. We discuss new measurements of the UV luminosity function at z≳ 10 and associated implications for early star formation. We then summarize what is being learned about the physical properties of early galaxies, with up-to-date discussions of the sizes, masses, ages, metallicities, abundance patterns, UV colors, dust properties, and ionizing sources in z≳ 5 galaxies. We review observational evidence for bursty star formation histories and describe prospects for characterizing the duty cycle with future observations. We provide a brief overview of the insight being gained through new detections of AGN in early galaxies. Finally we introduce the latest constraints on the contribution of galaxies to reionziation and discuss how JWST measurements of Lyα emission offer the potential to probe the earliest stages of the process. This review is meant to provide a broad introduction to those new to the observational study of very high redshift galaxies.

We characterize the JWST spectra of 61 galaxies at z = 9-14, including 30 newly confirmed galaxies. We directly compare the z > 9 spectroscopic properties against 401 galaxies at 6 < z < 9, with the goal of identifying evolution in the star formation histories and interstellar medium. We measure rest-UV emission-line properties and UV continuum slopes, while also investigating the rest-optical emission lines for the subset of galaxies at 9.0 < z < 9.6. With these spectra, we constrain the stellar masses, specific star formation rates (sSFRs), dust attenuation, and the average metallicity and abundance pattern of z > 9 galaxies. Our dataset indicates that the emission lines undergo a marked change at z > 9, with extremely large C III], H beta, and H gamma equivalent widths becoming 2 and 3 & times; more common at z > 9 relative to 6 < z < 9. Using the spectra, we infer the distribution of star formation rates (SFRs) on short (SFR3Myr) and medium (SFR3-50Myr) timescales, finding that rapid SFR upturns (large SFR3Myr/SFR3-50Myr ratios) are significantly more likely among z > 9 galaxies. These results may reflect a larger dispersion in UV luminosity at fixed halo mass and larger baryon accretion rates at z > 9, although other physical effects may also contribute. We suggest that the shift in star formation conditions explains the prevalence of extreme nebular spectra that have been detected at z > 9, with hard ionizing sources and nitrogen enhancements becoming more typical at the highest redshifts. Finally, we identify five z > 9 spectroscopically confirmed galaxies with red UV colors (beta greater than or similar to -1.5), revealing either a small population with moderate dust attenuation (tau(V) = 0.23-0.35) or very high density nebular-dominated galaxies with hot stellar populations.

We present an overview of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES), an ambitious program of infrared imaging and spectroscopy in the GOODS-S and GOODS-N deep fields, designed to study galaxy evolution from high redshift to cosmic noon. JADES uses about 770 hours of Cycle 1 guaranteed time largely from the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) instrument teams. In GOODS-S, in and around the Hubble Ultra Deep Field and Chandra Deep Field South, JADES produces a deep imaging region of ~45 arcmin$^2$ with an average of 130 hrs of exposure time spread over 9 NIRCam filters. This is extended at medium depth in GOODS-S and GOODS-N with NIRCam imaging of ~175 arcmin$^2$ with an average exposure time of 20 hrs spread over 8-10 filters. In both fields, we conduct extensive NIRSpec multi-object spectroscopy, including 2 deep pointings of 55 hrs exposure time, 14 medium pointings of ~12 hrs, and 15 shallower pointings of ~4 hrs, targeting over 5000 HST and JWST-detected faint sources with 5 low, medium, and high-resolution dispersers covering 0.6-5.3 microns. Finally, JADES extends redward via coordinated parallels with the JWST Mid-Infrared Instrument (MIRI), featuring ~9 arcmin$^2$ with 43 hours of exposure at 7.7 microns and twice that area with 2-6.5 hours of exposure at 12.8 microns For nearly 30 years, the GOODS-S and GOODS-N fields have been developed as the premier deep fields on the sky; JADES is now providing a compelling start on the JWST legacy in these fields.

We present the first robust helium (He) abundance measurements in star-forming galaxies at redshifts 1.6 ≲ z ≲ 3.3 using deep, moderate-resolution JWST/NIRSpec spectroscopy from the AURORA survey. We establish a high- z He sample consisting of 20 galaxies with multiple high-signal-to-noise-ratio (>5 σ ) He i emission-line detections, including the critical near-infrared λ 10833 line. This is the first study at high redshift leveraging λ 10833 to break degeneracies between temperature, electron density, optical depth, and He ^+ /H ^+ , enabling reliable He abundance determinations in the early Universe. We use a custom Markov Chain Monte Carlo framework incorporating direct-method electron temperature priors, extended optical depth ( τ _λ _3890 ) model grids up to densities of 10 ^6 cm ^−3 , and simultaneous fits of the physical conditions and He i /H i line ratios to derive ionic He ^+ /H ^+ abundances. Most of the AURORA galaxies follow the extrapolated z ∼ 0 He/H–O/H trend, indicating modest He enrichment by z ∼ 2–3. However, we identify a subpopulation of four galaxies that exhibit elevated He mass fractions (Δ Y > 0.03) without corresponding enhancements in N/O or α -elements (∼20% of the sample). This abundance pattern is inconsistent with enrichment from asymptotic giant branch stars, but favors early He enrichment from very massive stars ( M ≳ 100 M _⊙ ), which can eject He-rich, N-poor material via stellar winds and binary stripping in young stellar populations. We speculate that these elevated-He systems may represent an early phase of globular cluster (GC) formation where N enrichment is still lagging behind He production. This work demonstrates the power of JWST multi-line He i spectroscopy for tracing early stellar feedback, enrichment pathways, and GC progenitor signatures in the high-redshift Universe.

We report the discovery of a doubly imaged little red dot (LRD) candidate behind the galaxy cluster Abell 383, which we dub A383-LRD1. Initially classified as a dropout galaxy in HST imaging with several ground-based emission line detections placing it at z(spec) = 6.027, new JWST/NIRCam observations taken as part of the cycle 4 VENUS survey now reveal that the source consists of two underlying components. These consist of a red point-source with a V-shaped SED consistent with LRD selection criteria and a nearby (similar to 380 pc) compact blue companion, which was the main contributor to the previous rest-frame UV detections. Based on lensing symmetry and its SED, the LRD appears to lie at a similar redshift as well. The magnification of the two images of A383-LRD1 is mu(A) = 16.2 +/- 1.2 and mu(B) = 9.0 +/- 0.6, respectively, and the predicted time delay between them is Delta t(grav) = 5.20 +/- 0.14 yr (similar to 0.7 yr in the rest-frame). After correcting for the lensing magnification, we derived an absolute magnitude of M-UV,M- LRD = -16.8 +/- 0.3 for the LRD and M-UV,M- BC = -18.2 +/- 0.2 for the blue companion. We performed SED fits to both components, revealing the LRD to show the best fit with a black hole star (BH*) model and a substantial host galaxy, along with the blue companion with an extremely young, emission-line dominated star-forming nebula. If it is verified spectroscopically in the future, A383-LRD1 would represent the second known multiply imaged LRD detected to date, following A2744-QSO1. To our knowledge, it would also stand as the first LRD system with a confirmed detection of [C II]lambda 158 mu m emission from ALMA observations. Thanks to the lensing magnification, this system opens a unique door to studying the relation between a LRD, its host galaxy, and its environment. It represents a prime candidate for deep JWST spectroscopy and high-resolution ALMA follow-up observations.

The rest-frame ultraviolet (UV) spectra of star-forming galaxies are increasingly important as they become one of the primary windows to probe the physical properties of cosmic dawn (z > 8) galaxies with the James Webb Space Telescope. However, the systematic discrepancies between UV and optical gas-phase metallicity measurements remain poorly understood in the local universe, partly due to challenges in achieving precise comparisons between UV and optical spectra for the same objects. In this work, we introduce a novel method that leverages the He II lambda 1640 and He II lambda 4686 nebular emission lines to achieve accurate aperture and reddening corrections between UV and optical spectra. Here we apply this method to three nearby Blue Compact Dwarf (BCD) galaxies. Our results demonstrate that this approach enables precise measurements, with electron temperatures (T-e) derived from UV and optical spectra exhibiting closer agreement compared to previous studies, and O/H abundance agreeing within 0.1 dex. However, two BCDs appear to have lower UV-based electron temperatures T-e1666 < T-e4363, in contrast to expectations from the temperature fluctuation model. We consider a variety of possible explanations for these unphysical temperatures - differential dust attenuation, aperture differences, and spatial extent of emission lines - but no suitable cause is identified. These findings suggest a complex gaseous environment associated with star formation, and underscore the need for additional observations to further investigate the nature of He II nebular emission and address the systematic issues between UV and optical nebular properties. Nonetheless, the close empirical agreement of these results indicates that UV- and optical-based nebular temperature and abundance measurements can be reliably compared within 0.1 dex, providing a solid foundation for evolutionary studies from the local Universe to cosmic dawn.

ABSTRACT Strong $\text{Ly}\, \alpha$ emission observed from galaxies when the Universe is expected to be highly neutral is thought to trace large ionized regions that facilitate the transmission of $\text{Ly}\, \alpha$ through the intergalactic medium (IGM). In this work, we use deep JWST$\text{Ly}\, \alpha$ spectroscopy to constrain the size of a candidate ionized bubble at $z\sim 8.7$ in the Extended Groth Strip (EGS) field, with a potential radius of $R_\mathrm{ b}=2$ physical Mpc (pMpc) or larger. We measure a photometric galaxy density and find that the volume is a factor of ${\sim} 2.5\text{-}3.6$ overdense, suggesting that there may be a large population of galaxies capable of creating an $R_\mathrm{ b}\sim 2$ pMpc bubble. Then, we infer the $\text{Ly}\, \alpha$ transmission through the IGM for galaxies in the EGS volume using our deep spectroscopy, finding $\mathcal {T}_{\small IGM}=0.26_{-0.14}^{+0.25}$. This transmission is consistent with the average at $z\sim 9$ and is mildly inconsistent with the transmission expected for an $R_\mathrm{ b}\sim 2$ pMpc bubble ($\mathcal {T}_{{\small IGM},2\, \text{pMpc}}=0.53\text{-}0.63$), implying that such a large bubble is unlikely to be present. However, the photometric galaxy density in the EGS field is larger than in several other deep fields. This overdensity and the moderate $\text{Ly}\, \alpha$ transmission may be consistent with smaller, $R_\mathrm{ b}\sim 0.5\text{-}1$ pMpc bubbles in EGS. This additionally motivates the need for future wider area $\text{Ly}\, \alpha$ spectroscopy in EGS and other fields to obtain a more representative understanding of the sizes of ionized bubbles in the early stages of reionization, and the properties of the galaxies that create them.

Measuring the ionizing photon production efficiency xi(ion,0)-the ratio of the ionizing photon output rate Q(H)0 to the UV continuum luminosity L-UV-in galaxies at z > 6 is crucial for constraining their contribution to cosmic reionization. We present integrated and spatially resolved measurements of xi(ion,0) for 12 exceptionally bright (M-UV similar to -22 mag) star-forming galaxies at z similar to 7 from the Reionization Era Bright Emission Line Survey (REBELS). These measurements are based on JWST NIRSpec/Integral Field Unit PRISM spectroscopy, probing the rest-frame UV and optical regime. Notably, in 8 of the 12 galaxies, the spectral coverage includes H alpha, enabling self-consistent dust attenuation estimates in both the ionized gas and stellar continuum via the Balmer decrement and rest-UV slope, respectively. We find global log(xi(ion,0)) values ranging from 25.19 +/- 0.11 to 25.61 +/- 0.11, with a weighted mean of 25.44 +/- 0.15, consistent with the canonical value of similar to 25.3. Using a sample of 25 star-forming clumps within these galaxies, we explore local variations in the ionizing photon production efficiency, finding a broader range, from 24.52 +/- 0.21 to 26.18 +/- 0.61. We identify strong correlations between xi(ion,0) and the specific star formation rate, star formation surface density, H beta equivalent width, and stellar mass. Clumps with the highest xi(ion,0) exhibit EW0(H beta) >= 150 & Aring;, consistent with young stellar ages. From previous Ly alpha measurements in three galaxies, we estimate a typical Ly alpha escape fraction of f(esc,Ly alpha) similar to 2%, suggesting similar or lower escape fractions for LyC photons. Combining this with our H alpha measurements, we infer ionized bubble sizes similar to 1 pMpc, aligned with expectations from Ly alpha-detected systems and reionization models.

We present deep ALMA Band 7 observations of the $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ line and underlying dust continuum emission in four UV-bright, gravitationally lensed (magnification $\mu = 1.4-3.8$), JWST-selected galaxies at $z = 8.5 - 10.3$, with observed magnitudes $-22.5 \lesssim M_\mathrm{UV} \lesssim -20.5$. $\mathrm{[O\,III]}$ is confidently detected in UNCOVER-10646 at $z=8.5080 \pm 0.0011$ ($15\sigma$) and DHZ1 at $z=9.3113 \pm 0.0006$ ($6\sigma$), with both being intrinsically luminous systems [$L_\mathrm{[O\,III]} = (1.1 - 1.6) \times 10^9\,L_\odot$] that follow the local $\mathrm{[O\,III]}$-SFR relation. $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ remains undetected in the two $z>10$ targets, including in the $z=10.07$ X-ray AGN UHZ1, where we obtain a deep limit of $L_\mathrm{[O\,III]} < 6 \times 10^7\,L_\odot$. Dust emission is not detected in any individual source nor in a stack ($<3\sigma$). The high S/N $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ detection in UNCOVER-10646 uniquely reveals an additional broad component ($\mathrm{FWHM} = 1366_{-329}^{+473}\,\mathrm{km/s}$; $\Delta\mathrm{BIC}\approx20$) indicative of an ionized outflow. We infer a high outflow rate of $\dot{M}_\mathrm{out} = 128_{-46}^{+80}\,M_\odot\,\mathrm{yr}^{-1}$, corresponding to a mass loading factor $\eta = \dot{M}_\mathrm{out}/\mathrm{SFR} = 2.9_{-1.0}^{+1.8}$ that matches or exceeds theoretical predictions and JWST-based studies of ionized outflows at high redshift. While high-resolution ALMA follow-up is required to confirm and spatially resolve the outflow, this first systematic study at $z>8$ highlights the unique diagnostic power of $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ in characterizing galaxies in the early Universe.

We present ultra-deep JWST spectroscopy of GN-z11 (z=10.6) obtained through the SPURS Cycle 4 Large Program, providing the deepest rest-UV view yet obtained of a galaxy at z>10. GN-z11 was previously found to be nitrogen-enhanced with detectable Lyα. The SPURS spectrum reveals P-Cygni stellar wind features and broad He II emission that are jointly reproduced by stellar population models incorporating very massive stars (VMS; >100 M_⊙) at low metallicity and young ages (≲3 Myr). We also detect a broad (FWHM=1670 km s^-1) component to N IV] λ1486, now seen in several nitrogen emitters, potentially arising from dense WN winds or LBV-like outbursts associated with a population of VMS in a dense environment, though an AGN-driven wind cannot be excluded. In either scenario, this broad component may trace the gas producing GN-z11's nitrogen enhancement. Rest-UV absorption lines reveal a fast (∼500 km s^-1), highly ionized outflow and a negligible neutral gas covering fraction. We resolve the weak Lyα emission (EW=5.6 Å, f_ esc,Lyα=2.7%), finding a broad red wing (44% of flux at >500 km s^-1) that should experience reduced IGM damping wing suppression and help explain Lyα visibility at z>10. Fine-structure O I* λ1304 emission indicates dense neutral gas near a subset of the ionizing sources, which may also scatter Lyα to the large observed velocities. The weak low-ionization absorption favors a picture in which this dense neutral gas is confined to a compact nuclear region. Together, these results are consistent with a rapid burst of star formation building up the dense nuclear regions and surrounding clusters in GN-z11.

We report the discovery of a doubly imaged little red dot (LRD) candidate behind the galaxy cluster Abell 383, which we dub A383-LRD1. Initially classified as a dropout galaxy in HST imaging with several ground-based emission line detections placing it at zspec = 6.027, new JWST/NIRCam observations taken as part of the cycle 4 VENUS survey now reveal that the source consists of two underlying components. These consist of a red point-source with a V-shaped SED consistent with LRD selection criteria and a nearby (∼380 pc) compact blue companion, which was the main contributor to the previous rest-frame UV detections. Based on lensing symmetry and its SED, the LRD appears to lie at a similar redshift as well. The magnification of the two images of A383-LRD1 is μA = 16.2 ± 1.2 and μB = 9.0 ± 0.6, respectively, and the predicted time delay between them is Δtgrav = 5.20 ± 0.14 yr (∼0.7 yr in the rest-frame). After correcting for the lensing magnification, we derived an absolute magnitude of MUV, LRD = −16.8 ± 0.3 for the LRD and MUV, BC = −18.2 ± 0.2 for the blue companion. We performed SED fits to both components, revealing the LRD to show the best fit with a black hole star (BH*) model and a substantial host galaxy, along with the blue companion with an extremely young, emission-line dominated star-forming nebula. If it is verified spectroscopically in the future, A383-LRD1 would represent the second known multiply imaged LRD detected to date, following A2744-QSO1. To our knowledge, it would also stand as the first LRD system with a confirmed detection of [C II]λ158 μm emission from ALMA observations. Thanks to the lensing magnification, this system opens a unique door to studying the relation between a LRD, its host galaxy, and its environment. It represents a prime candidate for deep JWST spectroscopy and high-resolution ALMA follow-up observations.

We present Keck/MOSFIRE H-band spectroscopic measurements covering the [CIII]1907, CIII]1909 doublet for a sample of 8 z 7 spectroscopically-confirmed star-forming galaxies drawn from the Reionization Era Bright Emission Line Survey (REBELS). This sample is notable for its bright median UV luminosity (Muv=-22.5 AB) and large median stellar mass (log(Mstar/Msun)=9.2). Although three sources show tentative evidence of a CIII] detection, we obtain no confident detections for any of the 8 REBELS sources. The median [CIII]1907+CIII]1909 3-sigma upper limit in equivalent width (EW) for the REBELS-MOSFIRE sample is 6.5 AA, and a stack of their H-band MOSFIRE spectra yields a non-detection with an associated 3-sigma upper limit of 2.6 AA. These upper limits fall significantly below the CIII] EW measured in a composite spectrum of representative z 7 star-forming galaxies, as well as those measured for notable early star-forming galaxies such as GN-z11, GHZ2, GS-z12, and RXCJ2248-ID. The lack of strong CIII] emission can be understood within the context of the stellar populations of the REBELS galaxies, as well as the ionization conditions and gas-phase metallicity implied by rest-frame optical spectroscopic properties ([OIII]+Hb EWs, and [OIII]5007/[OII]3727 and [NeIII]3869/[OII]3727 line ratios). The REBELS-MOSFIRE sample represents the higher-mass, higher-metallicity, lower-excitation tail of the z 7 galaxy population, whose ionizing properties must be fully characterized to constrain the role of star-forming galaxies during cosmic reionization.

We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (similar to 10%Z circle dot), lensed, compact (Reff similar to 20 pc) galaxy RXCJ2248 at z = 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 [O iii] components (FWHM similar to 700-3000 km s-1). We detect broadened He ii lambda 1640 and lambda 4687 (FWHM similar to 530 km s-1) and strong N iii lambda 4642 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(O/H)=7.753 +/- 0.025 ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( log(N/O)=-0.391 +/- 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 (similar to 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-z implies a similar to 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.