El Gordo (ACT-CL J0102-4915) is a massive galaxy cluster with two major mass components at redshift z = 0.87. Using spectral energy distribution fitting results from JWST/NIRCam photometry, the fraction of quenched galaxies in this cluster was measured in two bins of stellar mass: 9 <= log(M-* /M-circle dot ) < 10 and 10 log(M /M ) < 12. While there is no correlation between the quenched fraction and angular separation from the cluster's overall center of mass, there is a correlation between the quenched fraction and angular separation from the center of the nearest of the two mass components for the less-massive galaxies. This suggests that environmental quenching processes are in place at z similar to 1, and that dwarf galaxies are more affected by those processes than massive galaxies.

We present a photometric analysis of globular clusters (GCs) in the massive galaxy cluster MACS J0416.1−2403 ( z = 0.397) using deep JWST/NIRCam imaging from the PEARLS program. Point-spread function photometry was performed in the short wavelength filters, F090W, F115W, F150W, and F200W, yielding a catalog of ∼3 × 10 ^3 unresolved, point-like sources consistent with a GC population. Artificial-star tests indicate 80% completeness at F200W ≃ 30.36 mag. The color–magnitude diagrams show a narrow GC sequence well reproduced by PARSEC single-stellar-population models spanning ages of 5–9 Gyr and metallicities from [M/H] ≈ −2.0 to +0.2, consistent with evolved GC systems at this redshift. The GC luminosity function follows a log-normal form truncated by incompleteness at the faint end. The brightest sources extend slightly beyond the locus of classical GCs, suggesting a small number of ultracompact dwarf-like systems or stripped nuclei, while the bulk of the population exhibits the luminosities and colors expected for mature GCs at z ≃ 0.4.

As part of the SKYSURF Hubble Space Telescope (HST) Legacy Archival programme we present galaxy number counts which yield measurements of the extragalactic background light (EBL) at 15 different wavelengths. We have processed 82,752 HST images across 23 filters into 16 686 mosaics using the same software and processing pipeline throughout. Using 17/23 filters that give reliable galaxy counts, we constrain the integrated galaxy light (IGL) with a 1.4-9 per cent error between 0.3 and 1.6 mu m in combination with 8 bands from WAVES (Wide Area VISTA Extragalactic Survey) and DEVILS (Deep Extragalactic Visible Legacy Survey). While HST was never intended to undertake large area surveys, through extensive quality control and filtering, we were able to extract a reliable and representative sample of fields distributed across the sky. Our final catalogues cover a combined approximate to 19.6 deg2 , with individual filters covering areas ranging from approximate to 0.16-7.0 deg2 . The combination of numerousindependentsight-lines and area coverage allows usto reduce cosmic variance uncertainties in deep number counts to 0.21-1.8 per cent. For the first time we are able to establish a measurement of the IGL, 8.85 +/- 0.30 nW m-2 sr-1, at 0.59 mu m using HST data. We obtain a cosmic optical background value of 25.36 +/- 0.52 nW m-2 sr-1. Different techniques used to measure the COB, both directly and indirectly, have recently converged indicating that the COB arises almost exclusively from processes within galaxies. This in combination with the recent values reported from New Horizons and very high energy (VHE) constraints leaves very little room for any diffuse emission coming from outside the Milky Way

Galaxy mergers are key drivers of galaxy formation and evolution, including triggering active galactic nucleus (AGN) and star formation to a still unknown degree. We thus investigate the impact of galaxy mergers on star formation and AGN activity using 3330 galaxies at z = 4.5-8.5 from eight James Webb Space Telescope fields (CEERS, JADES GOODS-S, NEP-TDF, NGDEEP, GLASS, El-Gordo, SMACS-0723, and MACS-0416), covering an unmasked area of 189 arcmin(2). We focus on star formation rate (SFR) enhancement, AGN fraction, and AGN excess in close pairs defined by Delta z < 0.3 and projected separations r(p) < 100 kpc, relative to non-merger samples. Close pairs with mass ratios greater than 1:4 are used for the SFR-enhancement analysis, whereas no mass-ratio constraint is applied for the AGN fraction and AGN excess measurements. We find SFR enhancement occurs only at r(p) < 20 kpc, with values 0.25 +/- 0 .10 dex and 0 .26 +/- 0 .11 dex above non-merger medians for z = [4.5 , 6.5] and z = [6.5 , 8.5] , respectively. No other statistically significant enhancements in galaxy sSFR or stellar mass are observed at any projected separation or redshift. We also compare observational results with predictions from the SC-SAM simulation, finding no evidence of star formation enhancement in simulations at any separation. Lastly, we examine the fraction and excess of AGNs identified through photometric spectral energy distributions (SED) fitting (Type-I) and BPT diagnostics (Type-II). We find 48(-7)(+33) % of Type-I and 44(-20)(+26)% of Type-II AGNs have a close companion within r(p) < 50 kpc and Delta z < 0.3.Furthermore, 73(-32)( +27)% of AGNs have companions within 100 kpc. Relative to isolated galaxies, we measure an AGN excess factor of 1.26(-0.04)(+0.15 )for Type-I and 1.34(-0.11 )(+0.23)for Type-II AGNs in close pairs, suggesting notable AGN enhancement in galaxy pairs at these higher redshifts.

We describe the drizzling pipeline and contents of the drizzled database for Hubble Space Telescope Cycle 27–29 Archival Legacy project “SKYSURF,” the largest archival project ever approved for Hubble. SKYSURF aims to investigate the extragalactic background light using all 143,914 ACSWFC, WFC3UVIS, and WFC3IR images that have been taken by Hubble since its launch in 2002. SKYSURF has produced 38,027 single-visit mosaics and 7893 multivisit mosaics across 28 ACSWFC, WFC3UVIS, and WFC3IR filters using nonstandard drizzling methods, which include preserving the lowest sky-level of each visit/group in the drizzled products, applying wider apertures for cosmic-ray rejection, correcting effects caused by charge transfer efficiency degradation, and removing potential light gradients from input images via sky-map subtraction. We generate source catalogs for all drizzled products with SExtractor and provide updated star–galaxy separation parameters and integrated galaxy light (IGL) estimates for 25 of the 28 SKYSURF filters (wavelength range 0.2–1.7 μ m) using a novel IGL fitting method made possible by the vast SKYSURF dataset. We discuss the data processing and data analysis challenges encountered, detail our solutions, and offer suggestions that may facilitate future large-scale IGL investigations with Webb, SPHEREx, and Roman.

We present 21 transients from our three-epoch, four-band NIRCam observations covering 14.16 arcmin ^2 in the Spitzer IRAC Dark Field (IDF), taken by the JWST Prime Extragalactic Areas for Reionization and Lensing Science program with a time cadence of ∼6 months. A separate Hubble Space Telescope program provided Advanced Camera for Surveys optical imaging contemporaneous with the second and third epochs of the NIRCam observations. The NIRSpec spectroscopy on three transients confirmed a Type Ia supernova at z = 1.63 and the host galaxies of the other two at z = 2.64 and 1.90, respectively. Combining these with the photometric redshifts ( z _ph ) of the host galaxies in the rest of the sample, we find that the transients are in either a “mid- z ” group at z > 1.6 with M _V ≲ − 16.0 mag or a “low- z ” group at z < 0.4 with M _H ≳ − 14.0 mag. The mid- z transients are consistent with supernovae. In contrast, the low- z transients’ luminosities fall in the range of the so-called “gap transients” between supernovae and novae. However, this latter conclusion is only tentative due to possible catastrophic failures in z _ph that could bias them to low- z . Conversely, if they are indeed at z < 0.4, it would be worth studying similar transients in the future. Our work further demonstrates the power of NIRCam in transient science and also shows that it would be more fruitful to carry out a long-term monitoring program with more passbands, a higher cadence, and prompt follow-up spectroscopy. Being in the continuous viewing zone of the JWST, the IDF is an ideal field for this purpose.

The cosmic star formation history (CSFH) and cosmic active galactic nuclei (AGN) luminosity history (CAGNH) are self consistently measured at z = 5.5-13.5. This is achieved by analyzing galaxies detected by the James Webb Space Telescope from approximate to 400arcmin2 fields from the Prime Extragalactic Areas of Reionization and Lensing Science, Cosmic Evolution Early Release Science, Next Generation Deep Extragalactic Exploratory Public, JWST Advanced Deep Extragalactic Survey, and Public Release IMaging for Extragalactic Research surveys. In particular, the combination of spectral energy distribution fitting codes, EAZY and ProSpect, is employed to estimate the photometric redshifts and astrophysical quantities of 3751 distant galaxies, from which we compute the stellar mass, star formation rate, and AGN luminosity distribution functions in four redshift bins. Integrating the distribution functions, we find that the CSFH rises by approximate to 1 dex over z = 13.5-5.5, and the CAGNH rises by approximate to 1 dex over z = 10.5-5.5. We connect our results of the CSFH and CAGNH at z = 13.5-5.5 to that from z = 5-0 to determine the summary of greater than or similar to 13 Gyr of star formation and AGN activity, from the very onset of galaxy formation to the present day.

We present JWST NIRSpec integral field spectroscopy observations of the z = 5.89 quasar NDWFS J1425+3254 from 0.6-5.3 mu m, covering the rest-frame ultraviolet and optical at a spectral resolution of R similar to 100. The quasar has a black hole mass of M-BH = (1.4(-1.0)(+3.1)) x 10(9) M-circle dot and an Eddington ratio of L-Bol/L-Edd = 0.3(-0.2)(+0.6), as implied from the broad Balmer H alpha and H beta lines. The quasar host has significant ongoing obscured star formation, as well as a quasar-driven outflow with velocity 6050(-630)(+460) km s(-1) and ionised outflow rate of 1650(-1230)(+130) M-circle dot yr(-1). This is possibly one of the most extreme outflows in the early Universe. The data also reveal that two companion galaxies are merging with the quasar host. The north-eastern companion galaxy is relatively old and very massive, with a luminosity-weighted stellar age of 65(-4)(+9) Myr, stellar mass of (3.6(-0.3)(+0.6))x10(11) M circle dot , and star-formation rate (SFR) of similar to 15-30 M-circle dot yr(-1). A bridge of gas connects this companion galaxy and the host, confirming their ongoing interaction. A second merger is occurring between the quasar host and a much younger companion galaxy to the south, with a stellar age of 6.7 +/- 1.8 Myr, stellar mass of (1.9 +/- 0.4)x10(10) M-circle dot, and SFR of similar to 40-65 M-circle dot yr(-1). There is also another galaxy in the field, likely in the foreground at z = 1.135, which could be gravitationally lensing the quasar with a magnification of 1 < mu < 2 and, thus, < 0.75 mag. Overall, the system is a 'train-wreck' merger of three galaxies, with star formation and extreme quasar activity that were likely triggered by these ongoing interactions.

The combination of the z = 0–13.5 cosmic star formation history and active galactic nuclei (AGN) luminosity history, as inferred by the James Webb Space Telescope, is connected to the cosmic spectral energy distribution (SED) to explore the sources of reionization. We compute the redshift evolution of the corresponding cosmic ionizing photon emissivity, the neutral fraction, and the cosmic microwave background optical depth. We use the generative SED modelling code P ro S pect to bracket the ionizing emissivity between escape fractions of f esc = 1%–100% for both the stars and AGN. Stars alone could have achieved reionization by z ≈ 6 with f esc ≳ 30% for solar metallicity ( Z = 0.02) stars or f esc ≳ 10% for metal-poor ( Z = 10 −4 ) stars. On the other hand, AGN by themselves would have struggled to produce sufficiently many ionizing photons even with f esc = 100%. A hybrid model containing both stars and AGN is explored, where we find the best fit (median±1 σ ) f esc = 12% ( 1 4 − 7 + 9 % ) for the stars and f esc = 63% ( 6 0 − 32 + 28 % ) for the AGN, maintained at all redshifts. In essence, the joint growth of stellar mass and supermassive black holes produces neither more nor fewer ionizing photons than needed to reionize ≳99% of the intergalactic medium by z ≈ 6.

We present a full analysis of galaxy major merger pair fractions, merger rates, and mass accretion rates, thus uncovering the role of mergers in galaxy formation at the earliest previously unexplored epoch of 4.5 < z < 11.5. We target galaxies with masses log10 (M-*/M-circle dot) = 8.0-10.0, utilizing data from eight JWST Cycle-1 fields [CEERS (Cosmic Evolution Early Release Science Survey), JADES (JWST Advanced Deep Extragalactic Survey) GOODS-S, NEP-TDF (North Ecliptic Pole Time-Domain Field), NGDEEP (Next-Generation Deep Extragalactic Exploratory Public Survey), GLASS (Grism Lens Amplified Survey from Space), El-Gordo, SMACS-0723, MACS-0416], covering an unmasked area of 189.36 arcmin2. We develop a new probabilistic pair-counting methodology that integrates full photometric redshift posteriors and corrects for detection incompleteness to quantify close pairs with physical projected separations between 20 and 50 kpc. Our analysis reveals an increase in pair fractions up to z=8, reaching 0.211 +/- 0.065, followed by a statistically flat evolution to z=11.5. We find that the galaxy merger rate increases from the local Universe up to z=6 and then stabilizes at a value of similar to 6 Gyr(-1) up to z=11.5. The redshift evolution of both pair fractions and merger rates is well described by a power-law plus exponential model. In addition, we measure that the average galaxy increases its stellar mass due to mergers by a factor of 2.77 +/- 0.99 from redshift z=10.5 to z=5.0. Lastly, we investigate the impact of mergers on galaxy stellar mass growth, revealing that mergers contribute as much as 71 +/- 25 per cent to galaxy stellar mass growth. This indicates that mergers drive about half of galaxy assembly at high redshift.

A distinct power-law break is apparent at m _AB ∼ 21 in the deep near-infrared PEARLS-JWST galaxy counts. The break becomes more pronounced at longer wavelengths, with the slope flattening smoothly with apparent magnitude in the shortest band used at 0.9 μ m, and trending toward an increasingly broken slope by the longest wavelength passband of JWST’s Near Infrared Camera, 4.4 μ m. This behaviour is remarkably well predicted by the GALFORM semi-analytical model of galaxy formation. We use the model to diagnose the origin of this behaviour. The features that are responsible for the break are (1) the inherent break in the luminosity function (LF); (2) the change in the volume element with redshift; (3) the redshift-dependent nature of the k -correction (with 1 contributing to the existence of the break and 2–3 contributing to its shape). We study the contribution to these effects by their morphology using the bulge-to-total stellar mass ratio. The way in which bulge-dominated galaxies populate the bright end of the LF while disk-dominated galaxies dominate the faint end is preserved in the galaxy number counts, with a characteristic stellar mass at a break of ∼10 ^10 M _⊙ . The shape of the number counts is mainly driven by galaxies with relatively low redshift ( z ≲ 2) for a limit of m _AB ≲ 28. We give a comprehensive description of why the galaxy number counts in the near-infrared PEARLS-JWST observation look the way they do and which population of galaxies is dominant at each apparent magnitude.

We utilize deep JWST Near Infrared Camera (NIRCam) observations for the first direct constraints on the Galaxy Stellar Mass Function (GSMF) at z > 10. Our EPOCHS v1 sample includes 1120 galaxy candidates at 6.5 < z < 13.5 taken from a consistent reduction and analysis of publicly available deep JWST NIRCam data covering the Prime Extragalactic Areas for Reionization Science, CEERS, GLASS, JADES GOOD-S, NGDEEP, and SMACS0723 surveys, totaling 187 arcmin2. We investigate the impact of spectral energy distribution fitting methods, assumed star formation histories (SFHs), dust laws, and priors on galaxy masses and the resultant GSMF. While our fiducial GSMF agrees with the literature at z < 13.5, we find that the assumed SFH model has a large impact on the GSMF and stellar mass density (SMD), finding a 0.75 dex increase in the SMD at z = 10.5 between a flexible nonparametric and standard parametric SFH. Overall, we find a flatter SMD evolution at z >= 9 than some studies predict, suggesting a rapid buildup of stellar mass in the early Universe. We find no incompatibility between our results and those of standard cosmological models, as suggested previously, although the most massive galaxies may require a high star formation efficiency. We find that the "little red dot" galaxies dominate the z = 7 GSMF at high masses, necessitating a better understanding of the relative contributions of active galactic nucleus and stellar emission. We show that assuming a theoretically motivated top-heavy initial mass function (IMF) reduces stellar mass by 0.5 dex without affecting fit quality, but our results remain consistent with existing cosmological models with a standard IMF.

In a recent paper, we parametrized the evolution of the star formation rate dispersion (Ostr) across the specific star formation. rate-stellar mass plane (sSFR-M.) using the Deep Extragalactic Visible Legacy Survey (DEVILS)-suggesting that the point at which the minimum in the dispersion occurs (M*(sigma-min)) defines a boundary between different physical mechanisms affecting galaxy evolution. Here, we expand upon that work to determine the movement of galaxies through the sSFR-M, plane using their recent star formation histories (SFHs) and explore how this leads to the observed OSFR-M-*. relation. We find that galaxies in subregions of the sSFR-M, plane show distinctly different SFHs, leading to a complex evolution of the sSFR-M-*. plane and star-forming sequence (SFS). However, we find that selecting galaxies based on stellar mass and position relative to SFS alone (as is traditionally the case), may not identify sources with common recent SFHs, and therefore propose a new selection methodology. We then use the recent SFH of galaxies to measure the evolution of the SFS, showing that it has varying contributions from galaxies with different SFHs that lead to the observed changes in slope, normalization, and turnover stellar mass. Finally, we determine the overall evolution of the sSFR-M, plane from 1 to today. In the second paper in this series, we will discuss physical properties of galaxies with common recent SFHs and how these lead to the observed OSFR-M-* relation and evolution of the s(SFR)-M-* plane.

Observations with the James Webb Space Telescope (JWST) reveal a previously unseen population of compact red objects, known as “little red dots“ (LRDs). We study a new photometrically selected sample of 124 LRDs in the redshift range z ∼ 3 - 10 selected from NIRCam coverage of the CEERS, NEP-TDF, JADES and JEMS surveys. For JADES, the NEP-TDF and CEERS, we compare SED models with and without AGN components and analyse the impact of an AGN component on the goodness of fit using the Bayesian information criterion (BIC). We find that whilst the χ^2 of the majority of models containing AGN components is improved compared to models without AGN components, we show that the BIC suggests models without AGN are a more appropriate fit to LRD SEDs, especially when MIRI data is available. We also measure LRD clustering in the CEERS field, JADES field, and NEP-TDF, where we compare the spatial distribution of LRDs and galaxies with Kolmogorov-Smirnov tests of equality of distribution. We find that the neighbourhood of LRDs tends to be less dense compared to galaxies at all selections and masses and at similar redshifts. We further measure upper limit estimates for the halo masses of LRDs using abundance matching. Whilst the population of LRDs could be a mixture of several different inherent populations, as a whole it does appear that these systems are mostly hosting compact galaxies or star clusters in formation.

We present an analysis of rest-frame UV continuum slopes, β , using a sample of 1011 galaxies at 6.5 < z < 13 from the EPOCHS photometric sample collated from the GTO PEARLS and public ERS/GTO/GO (JADES, CEERS, NGDEEP, GLASS) JWST/NIRCam imaging across 178.9 arcmin 2 of unmasked blank sky. We correct our UV slopes for the photometric error coupling bias using 200,000 power-law spectral energy distributions for each β = {−1, −1.5, −2, −2.5, −3} in each field, finding biases as large as Δ β ≃ −0.55 for the lowest signal-to-noise ratio galaxies in our sample. Additionally, we simulate the impact of rest-UV line emission (including Ly α ) and damped Ly α systems on our measured β , finding biases as large as 0.5–0.6 for the most extreme systems. We find a decreasing trend with redshift of β = −1.51 ± 0.08 − (0.097 ± 0.010) × z , with potential evidence for Population III stars or top-heavy initial mass functions in a subsample of 68 β + σ β < −2.8 galaxies. At z ≃ 11.5, we measure an extremely blue β ( M UV = −19) = −2.73 ± 0.06, deviating from simulations, indicative of low-metallicity galaxies with nonzero Lyman continuum escape fractions f esc,LyC ≳ 0 and minimal dust content. The observed steepening of d β / d log 10 ( M ⋆ / M ⊙ ) from 0.22 ± 0.02 at z ≃ 7 to 0.81 ± 0.13 at z ≃ 11.5 implies that dust produced in core-collapse supernovae at early times may be ejected via outflows from low-mass galaxies. We also observe a flatter d β / d M UV = 0.03 ± 0.02 at z ≃ 7 and a shallower d β / d log 10 ( M ⋆ / M ⊙ ) at z < 11 than seen by the Hubble Space Telescope, unveiling a new population of low-mass, faint galaxies reddened by dust produced in the stellar winds of asymptotic giant branch stars or carbon-rich Wolf–Rayet binaries.

We present the discovery, and initial lensing analysis, of a high-redshift galaxy-galaxy lensing system within the JWST-PEARLS/HST-TREASUREHUNT North Ecliptic Pole Time Domain Field (designated NEPJ172238.9 + 655143.1). The lensing geometry shears a z = 3 . 6 +/- 0 . 1 star-forming galaxy into a near-Einstein ring with a radius of 0.92 arcsec, consisting of 4 images, around a foreground massive elliptical galaxy at z = 1 . 258 +/- 0 . 005. The system is fortuitously located within the NIRISS F200W footprint of the PEARLS survey, enabling spectroscopic identification of the 8500 & Aring; TiO band in the foreground galaxy and allowing tight constraints to be placed on the redshift of the background galaxy based on its continuum detection and lack of strong emission lines. We calculate magnification factors of 2 . 6 < < 8 . 4 for the four images and a total lensing mass of (4 . 08 +/- 0 . 07) x 10(11) M (R). SED fitting of the foreground elliptical galaxy within the Einstein radius reveals a stellar mass of 1 . 26 x 10(11 )M (R) under a Kroupa IMF, providing 31 percent of the estimated lensing mass. Employing simple scaling relations and assumptions, an NFW dark matter halo is found to provide the correct remaining mass within 0 . 12(-0.09)(+ 0.21) dex. However, if a modified IMF for elliptical galaxies is employed (e.g. bottom-heavy or bottom-and-top-heavy), stellar mass estimations increase and can account for the majority of the lensing mass, reducing the need for dark matter. This system further demonstrates the new discovery space that the combined wavelength coverage, sensitivity and resolution of James Webb Space Telescope (JWST) now enables.

We present initial results from the 4.8 GHz Very Long Baseline Array (VLBA) survey of the JWST North Ecliptic Pole Time-Domain Field (TDF). From 106 radio sources found in the Karl G. Jansky Very Large Array observations in the TDF, we detected 12 sources (11% detection rate) at 3.3 $μ$Jy rms sensitivity and 4 mas resolution. Most detections exhibit pc-scale emission (less than 40 pc) with high VLBA/VLA flux density ratios and brightness temperatures exceeding 10$^5$ K, confirming non-thermal AGN activity. Spectral indices ($>$ -0.5) correlate with higher VLBA/VLA flux ratios, consistent with synchrotron emission from AGN coronae or jets. In the majority of our sources star formation contributes less than 50% of the total VLBA radio emission, with a few cases where the emission is almost entirely AGN-driven. Although the radio emission from radio quiet AGN is thought to be primarily driven by star formation, our VLBA observations confirm that there is also often a contribution at various levels from black hole driven AGN. Eight VLBA detections have JWST/NIRCam counterparts, predominantly early-type, bulge-dominated galaxies, which we use to get an estimate of the redshift and star formation rate (SFR). WISE colors indicate that VLBA detections are either AGN or intermediate-disk-dominated systems, while VLBA non-detections correspond to extended, star-forming galaxies. We compare SFRs derived from previous SCUBA-2 850 $μ$m observations with new JWST-based estimates, and discuss the observed discrepancies, highlighting JWST's improved capability to disentangle AGN activity from star formation.

We present initial results from the 4.8 GHz Very Long Baseline Array (VLBA) survey of the JWST North Ecliptic Pole Time-Domain Field (TDF). From 106 radio sources found in the Karl G. Jansky Very Large Array (VLA) observations in the TDF, we detected 12 sources (∼11% detection rate) at ∼3.3 μ Jy rms sensitivity and ∼4 mas resolution. Most detections exhibit parsec-scale emission (less than 40 pc) with high VLBA/VLA flux density ratios and brightness temperatures exceeding 10 ^5 K, confirming nonthermal active galactic nucleus (AGN) activity. Spectral indices α ≳ −0.5 correlate with higher VLBA/VLA flux ratios, consistent with synchrotron emission from AGN coronae or jets. In the majority of our sources, star formation contributes less than 50% of the total VLBA radio emission, with a few cases where the emission is almost entirely AGN driven. Although the radio emission from radio quiet AGN is thought to be primarily driven by star formation, our VLBA observations confirm that there is also often a contribution at various levels from black hole driven AGN. Eight VLBA detections have JWST/NIRCam counterparts, predominantly early-type, bulge-dominated galaxies, which we use to get an estimate of the redshift and star formation rate (SFR). Wide-field Infrared Survey Explorer colors indicate that VLBA detections are either AGN or intermediate-disk-dominated systems, while VLBA nondetections correspond to extended, star-forming galaxies. We compare SFRs derived from previous SCUBA-2 850 μ m observations with new JWST-based estimates, and discuss the observed discrepancies, highlighting JWST’s improved capability to disentangle AGN activity from star formation.

We present a structural analysis of 520 galaxy candidates at 6.5 < z < 12.5 with a signal-to-noise ratio of >10 σ in the F444W filter taken from the EPOCHS v1 sample, consisting of uniformly reduced deep JWST NIRCam data covering the CEERS, JADES GOODS-S, NGDEEP, SMACS-0723, GLASS, and PEARLS surveys. We use standard software to fit single Sérsic models to each galaxy in the rest-frame optical and extract their parametric structural parameters (Sérsic index, half-light radius, and axis ratio) and Morfometryka to measure their nonparametric concentration and asymmetry parameters. We find a wide range of sizes for these early galaxies, with galaxy sizes overall continuing to become progressively smaller in the high-redshift regime, following R e = 2.12 ± 0.28 1 + z − 0.67 ± 0.06 kpc. We further find a galaxy size–mass correlation up to z ∼ 12, with galaxies of a given mass also becoming smaller. Using nonparametric methods, we find that galaxy merger fractions, classified through asymmetry parameters, at these redshifts remain consistent with those in the literature, maintaining a value of f m ∼ 0.12 ± 0.07 showing little dependence with redshift when combined with the literature at z > 4. We find that galaxies that are smaller in size also appear rounder, with an excess of high axis ratio objects. Finally, we artificially redshift a subsample of our objects to determine how robust the observational trends we see are, determining that the observed trends are due to real evolutionary effects, rather than being a consequence of redshift effects.

We present compelling arguments – focusing on galaxy science – for preserving the main imagers and operational modes of the Hubble Space Telescope (HST) for as long as is technically feasible, to assure maximum complementarity to the James Webb Space Telescope (JWST), Roman, and Euclid. HST was designed to work well over the 0.1-1.6 μm wavelength range, and its unique UV-optical performance has fundamentally contributed to our understanding of galaxy assembly and the Cosmic Star Formation History (CSFH). While star-formation started at redshifts z ≳ 10, when the universe was less than 500 Myr old, the CSFH did not peak until z ≃ 1.9 (i.e., about 10 Gyr ago), and has steadily declined since that time. Hence, at least half of all stars in the universe formed it in the last 10 Gyrs where HST provides its unique rest-frame UV view of unobscured young, massive stars tracing cosmic star-formation, as well as unobscured Active Galactic Nuclei (AGN). HST thus uniquely probes (unobscured) young, hot, massive stars and AGN in galaxies, while JWST, Euclid and Roman reveal more advanced stages of older stellar populations, as well as relatively short-lived phases where galaxies produce and shed a lot of dust from intense star-formation, dusty AGN, and the very high redshift universe (z ≳ 10) not accessible by HST. HST is thus highly complementary to these other facilities, all of which took decades to build to ensure decades of operation. To maximize return on investment in these facilities, ways will need to be found to operate HST imaging instruments in all relevant modes for as long as possible into the JWST and Roman missions.