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Abstract We analyze several key rest-optical emission-line ratios in a sample of 828 galaxies as well as composite spectra from JADES DR3 in the range 1.4 < z < 7. These emission-line ratios include: [Oiii]λ5008/Hβ, [Nii]λ6585/Hα, [Sii]λλ6718, 6733/Hα, [Oi]λ6302/Hα, O32, R23, Ne3O2, and RO2Ne3. We find evidence for a harder ionizing spectrum atz ∼ 3.5 compared toz ∼ 2 at fixed gas-phase metallicity, resulting in a pronounced shift in the star-forming galaxy locus on the [Nii]/HαBaldwin-Phillips-Terlevich (BPT) diagram and the O32 versus R23 diagram. Atz ≳ 3.5, star-forming galaxies occupy a common locus, indicating that interstellar medium (ISM) ionizing conditions at fixed gas-phase metallicity do not evolve strongly at these early cosmic times. There is a connection between ISM ionizing conditions and the chemical abundance patterns (i.e.,α/Fe) in massive stars, providing the ionizing radiation field. Therefore, the lack of evolution in ISM ionizing conditions atz ≳ 3.5, followed by evolution towards a softer ionizing spectrum at fixed nebular metallicity as cosmic time proceeds toz ∼ 2 and lower redshift mirrors the chemical abundance patterns in Milky Way stars as a function of iron abundance. Our results highlight the diagnostic power of emission-line diagrams in the era of JWST to further our understanding of the ISM conditions into the Epoch of Reionization. 

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. 

We present the construction of a deep multiwavelength point-spread-function-matched photometric catalog in the Ultra-Deep Survey (UDS) field following the final UKIDSS UDS release. The catalog includes photometry in 24 filters, from the MegaCam-uS 0.38 μm band to the Spitzer-IRAC 8 μm band, over ~0.9 deg2 and with a 5-sigma depth of 25.3 AB in the K-band detection image. The catalog, containing ~188,564 (136,235) galaxies at 0.28 and K-band total magnitude K<25.2 (24.3) AB, enables a range of extragalactic studies. We also provide photometric redshifts, corresponding redshift probability distributions, and rest-frame absolute magnitudes and colors derived using the template-fitting code eazy-py. Photometric redshift errors are less than 3%‑4% at z<4 across the full brightness range in the K band and stellar mass range 8 

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 Theoretical models predict thatz≳ 6 quasars are hosted in the most massive halos of the underlying dark matter distribution and thus would be immersed in protoclusters of galaxies. However, observations report inconclusive results. We investigate the 1.1 proper-Mpc²environment of thez= 7.54 luminous quasar ULAS J1342+0928. We search for Lyman-break galaxy (LBG) candidates using deep imaging from the Hubble Space Telescope (HST) in the Advanced Camera for Surveys (ACS)/F814W, Wide Field Camera 3 (WFC3)/F105W/F125W bands, and Spitzer/Infrared Array Camera at 3.6 and 4.5μm. We report a $z_{\mathrm{phot}}={7.69}_{-0.23}^{+0.33}$ LBG with mag_F125W= 26.41 at 223 projected proper kpc (pkpc) from the quasar. We find no HST counterpart to one [Cii] emitter previously found with the Atacama Large millimeter/submillimeter Array (ALMA) at 27 projected pkpc andz_{[C II]}=7.5341 ± 0.0009 (Venemans et al. 2020). We estimate the completeness of our LBG candidates using results from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey/GOODS deep blank field searches sharing a similar filter setup. We find that >50% of thez∼ 7.5 Lyman-break galaxies (LBGs) with mag_F125W> 25.5 are missed due to the absence of a filter redward of the Lyman break in F105W, hindering the UV color accuracy of the candidates. We conduct a QSO-LBG clustering analysis revealing a low LBG excess of ${0.46}_{-0.08}^{+1.52}$ in this quasar field, consistent with an average or low-density field. Consequently, this result does not present strong evidence of an LBG overdensity around ULAS J1342+0928. Furthermore, we identify two LBG candidates with az_photmatching a confirmedz= 6.84 absorber along the line of sight to the quasar. All these galaxy candidates are excellent targets for follow-up observations with JWST and/or ALMA to confirm their redshift and physical properties. 

ABSTRACT We report the detection of cold dust in an apparently quiescent massive galaxy (log (M⋆/M⊙) ≈ 11) at z ∼ 2 (G4). The source is identified as a serendipitous 2 mm continuum source in a deep ALMA observation within the field of Q2343-BX610, a z = 2.21 massive star-forming disc galaxy. Available multiband photometry of G4 suggests redshift of z ∼ 2 and a low specific star formation rate (sSFR), log (SFR/M⋆)[yr−1] ≈ −10.2, corresponding to ≈1.2 dex below the z = 2 main sequence (MS). G4 appears to be a peculiar dust-rich quiescent galaxy for its stellar mass (log (Mdust/M⋆) = −2.71 ± 0.26), with its estimated mass-weighted age (∼1–2 Gyr). We compile z ≳ 1 quiescent galaxies in the literature and discuss their age–ΔMS and log (Mdust/M⋆)–age relations to investigate passive evolution and dust depletion scale. A long dust depletion time and its morphology suggest morphological quenching along with less efficient feedback that could have acted on G4. The estimated dust yield for G4 further supports this idea, requiring efficient survival of dust and/or grain growth, and rejuvenation (or additional accretion). Follow-up observations probing the stellar light and cold dust peak are necessary to understand the implication of these findings in the broader context of galaxy evolutionary studies and quenching in the early universe. 

Abstract We present the first results from Chemical Evolution Constrained Using Ionized Lines in Interstellar Aurorae (CECILIA), a Cycle 1 JWST NIRSpec/MSA program that uses ultra-deep ∼30 hr G235M/F170LP observations to target multiple electron temperature-sensitive auroral lines in the spectra of 33 galaxies atz∼ 1–3. Using a subset of 23 galaxies, we construct two ∼600 object-hour composite spectra, both with and without the stellar continuum, and use these to investigate the characteristic rest-optical (λ_rest≈ 5700–8500 Å) spectrum of star-forming galaxies at the peak epoch of cosmic star formation. Emission lines of eight different elements (H, He, N, O, Si, S, Ar, and Ni) are detected, with most of these features observed to be ≲3% the strength of Hα. We report the characteristic strength of three auroral features ([Nii]λ5756, [Siii]λ6313, and [Oii]λλ7322, 7332), as well as other semi-strong and faint emission lines, including forbidden [Niii]λλ7380, 7414 and permitted Oiλ8449, some of which have never before been observed outside of the local Universe. Using these measurements, we findT_e[Nii] = 13,630 ± 2540 K, representing the first measurement of electron temperature using [Nii] in the high-redshift Universe. We also see evidence for broad line emission with a FWHM of ${536}_{-167}^{+45}$ km s⁻¹; the broad component of Hαis 6.01%–28.31% the strength of the narrow component and likely arises from star-formation-driven outflows. Finally, we briefly comment on the feasibility of obtaining large samples of faint emission lines using JWST in the future. 

We present the first data release of the Canadian NIRISS Unbiased Cluster Survey (CANUCS), a JWST Cycle 1 GTO program targeting five lensing clusters and flanking fields in parallel (A370, MACS0416, MACS0417, MACS1149, and MACS1423; survey area ∼100 arcmin²), with NIRCam imaging, NIRISS slitless spectroscopy, and NIRSpec prism multiobject spectroscopy. Fields centered on cluster cores include imaging in eight bands from 0.9–4.4μm, alongside continuous NIRISS coverage from 1.15–2μm, while the NIRCam flanking fields provide five wide-band and nine medium-band filters for exceptional spectral sampling, all to ∼29 mag_AB. We also present JWST in Technicolor, a Cycle 2 follow-up GO program targeting three CANUCS clusters (A370, MACS0416, and MACS1149). The Technicolor program adds NIRISS slitless spectroscopy in F090W to the cluster fields while adding eight wide-, medium-, and narrowband filters to the flanking fields. This provides NIRCam imaging in all wide- and medium-band filters over ∼30 arcmin². This paper describes our data reduction and photometry methodology. We release NIRCam, NIRISS, and Hubble Space Telescope imaging, point-spread functions (PSFs), PSF-matched imaging, photometric catalogs, and photometric and spectroscopic redshifts. We provide lens models and stellar population parameters in up to 19 filters for ∼53,000 galaxies in the cluster fields, and ∼44,000 galaxies in up to 29 filters in the flanking fields. We further present 733 NIRSpec spectra and redshift measurements up toz = 10.8. Comparing against our photometric redshifts, we find catastrophic outlier rates of only 4%–7% and scatter ofσ_NMADof 0.01–0.03. 

Abstract We present spatially resolved Hubble Space Telescope grism spectroscopy of 15 galaxies at z ∼ 0.8 drawn from the DEEP2 survey. We analyze H α +[N ii ], [S ii ], and [S iii ] emission on kiloparsec scales to explore which mechanisms are powering emission lines at high redshifts, testing which processes may be responsible for the well-known offset of high-redshift galaxies from the z ∼ 0 locus in the [O iii ]/H β versus [N ii ]/H α Baldwin—Phillips—Terlevich (BPT) excitation diagram. We study spatially resolved emission-line maps to examine evidence for active galactic nuclei (AGN), shocks, diffuse ionized gas (DIG), or escaping ionizing radiation, all of which may contribute to the BPT offsets observed in our sample. We do not find significant evidence of AGN in our sample and quantify that, on average, AGN would need to contribute ∼25% of the H α flux in the central resolution element in order to cause the observed BPT offsets. We find weak (2 σ ) evidence of DIG emission at low surface brightnesses, yielding an implied total DIG emission fraction of ∼20%, which is not significant enough to be the dominant emission line driver in our sample. In general we find that the observed emission is dominated by star-forming H ii regions. We discuss trends with demographic properties and the possible role of α -enhanced abundance patterns in the emission spectra of high-redshift galaxies. Our results indicate that photoionization modeling with stellar population synthesis inputs is a valid tool to explore the specific star formation properties which may cause BPT offsets, to be explored in future work.