Yechi Zhang

The James Webb Space Telescope (JWST) has extended the frontier of galaxy detection to redshifts z > 11, finding a high abundance of UV-bright sources that challenge theoretical models. However, most current results come from just a few fields, introducing uncertainties due to cosmic variance. Here, we constrain z ∼ 7–14 UV luminosity functions (LFs) over ∼400 arcmin ² across 36 independent sight lines from Data Release 2 of BEACON, a JWST pure-parallel NIRCam multiband imaging survey. We identify 164 7 < z < 12 galaxy candidates: 150 F090W, 14 F115W, and no robust F150W dropouts. In the 11 pointings overlapping with public JWST spectroscopy, we find no contaminants, indicating a high purity in our sample. Our z ∼ 7.5 UV LF agrees with previous bright-end measurements but yields lower number densities at −21 ≤ M _UV ≤ −19. At z ∼ 10, our measurements are lower than most photometric JWST results but match spectroscopic constraints, consistent with the high purity of our selection. The LFs at z ∼ 7.5 and 10 are consistent with pre-JWST models, while our limits at z > 13 do not rule out a possible excess. We measure significant clustering of bright ( M _UV < −20.5) galaxies at 7 < z < 10. Fields hosting such sources are approximately 3 times more likely to be overdense relative to the full survey, implying that UV-bright galaxies preferentially reside in the most massive halos at these redshifts. Comparing with seminumerical simulations, we estimate that M _UV < −20.5 galaxies inhabit halos ∼0.8 dex less massive at z ∼ 11 than at z ∼ 8, consistent with a shift to higher star formation rates. However, their observed clustering exceeds predictions from pre-JWST luminosity–halo mass relations, suggesting these sources reside in more massive halos than previously modelled and/or multiple halo occupation.

We systematically search for galaxy overdensities using 20 independent fields with a minimum of six filters (F090W, F115W, F150W, F277W, F356W, and F444W) from BEACON, the JWST Cycle 2 NIRCam pure-parallel imaging survey. We apply an adaptive kernel-density estimation method that incorporates the full photometric redshift probability distribution function of each galaxy to map galaxy overdensities, and identify 207 significant (>4 σ ) overdensities at 1.5 < z < 5. We measure the quenched galaxy fraction, the average specific star formation rate (sSFR), the total dark matter mass, and the local galaxy density of each system. By investigating the correlation among these observables, we find that galaxy quenching proceeds in two paths. (i) Overdensities within more massive halos exhibit higher quenched fractions and lower averaged sSFRs. This trend weakens at z ≳ 2, consistent with cold gas streams penetrating shock-heated massive halos and sustaining star formation activity at early times. (ii) We also find a dependence of the same parameters on local densities at z < 2, where the quenched fraction increases and the sSFR decreases toward higher densities. The environmental trend in sSFR weakens at z ∼ 2–3 and shows tentative evidence for a reversal at z > 3, potentially due to a larger cold gas supply in earlier times. Our study reveals a complex interplay between individual galaxies and large-scale environmental properties, marking the onset of environmental effects on galaxy quenching in massive halos at cosmic noon.

We report the detection of Ly α in CANUCS-LRD-z8.6, a recently discovered active galactic nucleus (AGN) at z = 8.63 by R. Tripodi et al. (2025), in new NIRSpec/MSA G140H/F070LP observations. We detect broad Ly α emission (FWHM = 1540 ± 260 km s ⁻¹ ) near the systemic velocity, which suggests a large ionizing bubble, considering that the Universe is almost fully neutral at the redshift. Through Ly α line-shape modeling assuming a Strömgren sphere, we find a large bubble radius, R _b = 1 . 5 − 0.2 + 0.3 pMpc, and a moderately high Ly α escape fraction, f _esc = 11% ± 3%. The intrinsic line width is inferred to be broad (2200 ± 280 km s ⁻¹ ), likely originating in the broad-line region. Existing data indicate that CANUCS-LRD-z8.6 is within a mild overdensity, δ = 1 . 8 − 0.6 + 3.0 , suggesting that other galaxies in its proximity might have contributed to the formation of the bubble. The high N IV ] _{λ 1488} /C IV _{λ 1548} and N IV ] _{λ 1488} /O III ] _{λ 1661} line ratios measured in existing NIRSpec/PRISM data indicate nitrogen enrichment in this metal-poor, low-luminosity AGN. The spectroscopic features are overall similar to those of other nitrogen-rich galaxies discovered in the literature, such as GN-z11 and GHZ2/GLASSz12. This suggests that CANUCS-LRD-z8.6 may represent one of the evolutionary phases of those nitrogen-rich galaxies.

We present analyses of a nitrogen-enriched star-forming galaxy, ID60001, at z = 4.6928 based on James Webb Space Telescope/NIRSpec Multi-Object Spectroscopy and NIRCam photometry. From rest-frame optical emission lines we derive the nitrogen-to-oxygen (N/O) abundance ratio of ID60001 to be log ( N / O ) = − 0.7 6 − 0.03 + 0.03 ( [ N / O ] = 0.1 0 − 0.03 + 0.03 ), which is significantly elevated at the corresponding metallicity 12 + log ( O / H ) = 7.7 5 − 0.01 + 0.01 ( Z / Z _⊙ = 0.12) compared to local counterparts. We discuss possible scenarios for elevated N/O abundance in ID60001, including pristine gas inflow, Wolf–Rayet (W-R) stars, and oxygen depletion by Type II supernova winds. Based on the moderately broadened He ii λ 4686 emission line, galaxy morphology, and star formation history, we conclude that the elevated N/O abundance of ID60001 is likely originated from massive (>25 M _⊙ ) W-R stars that directly collapse into a black hole. We also stress the importance of reliable electron density measurements when deriving N/O abundance with rest-frame optical emission lines.

SBS 0335-052E is a young star-forming dwarf galaxy with a total stellar mass of M _* ≲ 10 ⁸ M _⊙ and an extremely low metallicity ( Z ∼ 1/40 Z _⊙ ), which has long been considered to be devoid of an active galactic nucleus (AGN). Here, we report the detection of temporal flux variability of SBS 0335-052E in near-infrared (NIR) 3–4 μ m bands on timescales of several years, showing dimming and brightening of up to 50% over 14 yr, based on archival data from the Wide-field Infrared Survey Explorer. Our spectral energy distribution (SED) fitting of archival ultraviolet (UV)-NIR photometry, including AGN SED models, indicates that the variable NIR emission arises from an edge-on AGN dust torus. The UV-optical emission from the accretion disk is obscured and does not reach us, leading to the dominance of the host galaxy’s young stellar population in the UV-optical wavelengths. This analysis favors the presence of a Compton-thick, heavily obscured AGN in SBS 0335-052E, consistent with its observed X-ray weakness. From the SED fitting, we estimate an AGN bolometric luminosity of L _bol = 1.2 × 10 ⁴³ erg s ⁻¹ , which implies a black hole (BH) mass of M _BH ≃ 10 ⁵ M _⊙ if the AGN is accreting at the Eddington limit. If confirmed, SBS 0335-052E would be the least massive galaxy known to host an AGN, likely harboring an intermediate-mass BH.

We present a spectroscopic redshift catalogue of sources within the Abell 2744 cluster field, derived from JWST/NIRISS observations, obtained as part of the GLASS-JWST Early Release Science programme. We describe the data reduction, the contamination modelling, and the source detection, as well as the data quality assessment, the redshift determination, and the validation. The catalogue consists of 354 secure and 134 tentative redshifts, of which 245 are new spectroscopic redshifts, spanning the range 0.1≤z≤8.2. These include 17 galaxies at the cluster redshift, one galaxy at z≈8, and a triply imaged galaxy at z = 2.653±0.002. Comparing against galaxies with existing spectroscopic redshifts (z_spec), we find a small offset of Δz=(z_spec−z_NIRISS)/(1+z_spec) =(1.3±1.6)×10⁻³. We also present a forced extraction tool (PYGRIFE) and a visualisation tool (PYGCG) to the community, to aid with the reduction and classification of grism data. This catalogue will enable future studies of the spatially resolved properties of galaxies throughout cosmic noon, including dust attenuation and star formation. As a first application of the catalogue, we discuss the spectroscopic confirmation of multiple image systems and the identification of multiple overdensities at 1<z<2.7.

We study outflows in 130 galaxies with −22 < M _UV < −16 at z = 3–9 identified in JWST NIRSpec and NIRCam WFSS data taken by the ERO, CEERS, FRESCO, GLASS, and JADES programs. We identify 30 out of the 130 galaxies with broad components of FWHM ∼ 200–700 km s⁻¹ in the emission lines of Hα and [O iii] that trace ionized outflows. Four out of the 30 outflowing galaxies are Type 1 AGN whose Hα emission lines include line profile components as broad as FWHM ≳ 1000 km s⁻¹, while one galaxy is identified as a Type 2 AGN by high ionization emission lines. With the velocity shift and line widths of the outflow broad lines, we obtain ∼80–500 km s⁻¹ for the outflow velocities. We find that the outflow velocities are slower than low-z galaxies with similar star formation rates, which may be explained by the low stellar masses of high-z galaxies. The outflow velocities of AGNs are large but not significantly different from the others. Interestingly, these outflow velocities are typically not high enough to escape from the galactic potentials, possibly suggesting fountain-type outflows. We estimate mass loading factors η to be 0.1–1, which are not particularly large, but comparable with those of z ∼ 1 outflows. The large fraction of galaxies with outflows (30% with high-resolution data) provides constraints on outflow parameters, suggesting a wide opening angle of ≳45° and a large duty cycle of ≳30%, which gives a picture of more frequent and spherical outflows in high-z galaxies.

We introduce the Bias-free Extragalactic Analysis for Cosmic Origins with NIRCam (BEACON) survey, a JWST Cycle 2 program allocated up to 600 pure-parallel hours of observations. BEACON explores high-latitude areas of the sky with JWST/NIRCam over ∼100 independent sight lines, totaling ∼0.3 deg², reaching a median F444W depth of ≈28.2 AB mag (5σ). Based on existing JWST observations in legacy fields, we estimate that BEACON will photometrically identify 25–150 galaxies at z > 10 and 500–1000 at z ∼ 7–10 uniquely enabled by an efficient multiple filter configuration spanning 0.9–5.0 μm. The expected sample size of z > 10 galaxies will allow us to obtain robust number density estimates and to discriminate between different models of early star formation. In this paper, we present an overview of the survey design and initial results using the first 19 fields. We present 129 galaxy candidates at z ≳7 identified in those fields, including 11 galaxies at z ≳10 and several UV-luminous (M _UV < −21 mag) galaxies at z ∼ 8. The number densities of z < 13 galaxies inferred from the initial fields are overall consistent with those in the literature. Despite reaching a considerably large volume (∼10⁵ Mpc³), however, we find no galaxy candidates at z > 13, providing us with a complimentary insight into early galaxy evolution with minimal cosmic variance. We publish imaging and catalog data products for these initial fields. Upon survey completion, all BEACON data will be coherently processed and distributed to the community along with catalogs for redshift and other physical quantities.

We present deep Subaru/FOCAS spectra for two extreme emission line galaxies (EELGs) at z ∼ 1 with strong [O iii] λ5007 emission lines, exhibiting equivalent widths (EWs) of 290 5 − 578 + 946 Å and 200 0 − 159 + 188 Å, comparable to those of EELGs at high redshifts that are now routinely identified with JWST spectroscopy. Adding a similarly large [O iii] EW ( 250 8 − 689 + 1487 Å) EELG found at z ∼ 2 in the JWST CEERS survey to our sample, we explore the physical origins of the large [O iii] EWs of these three galaxies with the Subaru spectra and various public data including JWST/NIRSpec, NIRCam, and MIRI data. While there are no clear signatures of active galactic nuclei (AGNs) identified by the optical line diagnostics, we find that two out of two galaxies covered by the MIRI data show strong near-infrared excess in the spectral energy distributions (SEDs), indicating obscured AGNs. Because none of the three galaxies show clear broad Hβ lines, the upper limits on the flux ratios of broad Hβ to [O iii] lines are small, ≲0.15 that are comparable with Seyfert 1.8–2.0 galaxies. We conduct Cloudy modeling with the stellar and AGN incident spectra, allowing a wide range of parameters, including metallicities and ionization parameters. We find that the large [O iii] EWs are not self-consistently reproduced by the spectra of stars or unobscured AGNs, but obscured AGNs that efficiently produce O⁺⁺ ionizing photons with weak nuclear and stellar continua that are consistent with the SED shapes.