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The first James Webb Space Telescope (JWST) Near InfraRed Camera imaging in the field of the galaxy cluster PLCK G165.7+67.0 (z = 0.35) uncovered a Type Ia supernova (SN Ia) at z = 1.78, called “SN H0pe.” Three different images of this one SN were detected as a result of strong gravitational lensing, each one traversing a different path in spacetime, thereby inducing a relative delay in the arrival of each image. Follow-up JWST observations of all three SN images enabled photometric and rare spectroscopic measurements of the two relative time delays. Following strict blinding protocols which oversaw a live unblinding and regulated postunblinding changes, these two measured time delays were compared to the predictions of seven independently constructed cluster lens models to measure a value for the Hubble constant, H0 = 71.8 + 9.2 − 8.1 km s−1 Mpc−1. The range of admissible H0 values predicted across the lens models limits further precision, reflecting the well-known degeneracies between lens model constraints and time delays. It has long been theorized that a way forward is to leverage a standard candle, but this has not been realized until now. For the first time, the lens models are evaluated by their agreement with the SN absolute magnifications, breaking degeneracies and producing our best estimate, H0 = 75.7−5.5+8.1 km s−1 Mpc−1. This is the first precise measurement of H0 from a multiply imaged SN Ia and only the second from any multiply imaged SN.

The PASSAGES (Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts) collaboration has recently defined a sample of 30 gravitationally lensed dusty star-forming galaxies (DSFGs). These rare, submillimeter-selected objects enable high-resolution views of the most extreme sites of star formation in galaxies at cosmic noon. Here, we present the first major compilation of strong lensing analyses using lenstool for PASSAGES, including 15 objects spanning z = 1.1–3.3, using complementary information from 0.″6-resolution 1.1 mm Atacama Large Millimeter/submillimeter Array and 0.″4 5 cm Jansky Very Large Array continuum imaging, in tandem with 1.6 μm Hubble and optical imaging with Gemini-S. Magnifications range from μ = 2 to 28 (median μ = 7), yielding intrinsic infrared luminosities of L IR = 0.2–5.9 × 1013 L ⊙ (median 1.4 × 1013 L ⊙) and inferred star formation rates of 170–6300 M ⊙ yr−1 (median 1500 M ⊙ yr−1). These results suggest that the PASSAGES objects comprise some of the most extreme known starbursts, rivaling the luminosities of even the brightest unlensed objects, further amplified by lensing. The intrinsic sizes of far-infrared continuum regions are large (R e = 1.7–4.3 kpc; median 3.0 kpc) but consistent with L IR–R e scaling relations for z > 1 DSFGs, suggesting a widespread spatial distribution of star formation. With modestly high angular resolution, we explore if these objects might be maximal starbursts. Instead of approaching Eddington-limited surface densities, above which radiation pressure will disrupt further star formation, they are safely sub-Eddington—at least on global, galaxy-integrated scales.

The cluster environment has been shown to affect the molecular gas content of cluster members, yet a complete understanding of this often subtle effect has been hindered due to a lack of detections over the full parameter space of galaxy star formation rates (SFRs) and stellar masses. Here, we stack CO(2–1) spectra of z ∼ 1.6 cluster galaxies to explore the average molecular gas fractions of galaxies both at lower mass (log(M*/M⊙) ∼ 9.6) and further below the star-forming main sequence (SFMS; ΔMS ∼ −0.9) than other literature studies; this translates to a 3σ gas mass limit of ∼7 × 109 M⊙ for stacked galaxies below the SFMS. We divide our sample of 54 z ∼ 1.6 cluster galaxies, derived from the Spitzer Adaptation of the Red-Sequence Cluster Survey, into nine groupings, for which we recover detections in 8. The average gas content of the full cluster galaxy population is similar to coeval field galaxies matched in stellar mass and SFR. However, when further split by CO-undetected and CO-detected, we find that galaxies below the SFMS have statistically different gas fractions from the field scaling relations, spanning deficiencies to enhancements from 2σ below to 3σ above the expected field gas fractions, respectively. These differences between z = 1.6 cluster and field galaxies below the SFMS are likely due to environmental processes, though further investigation of spatially resolved properties and more robust field scaling relation calibration in this parameter space are required.

More than 60 years have passed since the first formal suggestion to use strongly lensed supernovae (SNe) to measure the expansion rate of the Universe through time-delay cosmography. Yet, fewer than 10 such objects have ever been discovered. We consider the merits of a targeted strategy focused on lensed hyperluminous infrared galaxies, which are among the most rapidly star-forming galaxies known in the Universe. With star formation rates (SFRs) ∼200–6000 M⊙ yr−1, the ∼30 objects in the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts are excellent candidates for a case study, in particular, and have already led to the discovery of the multiply imaged SN H0pe. Considering their lens model-corrected SFRs, we estimate their intrinsic SN rates to be an extraordinary 1.8–65 yr−1 (core-collapse) and 0.2–6.4 yr−1 (Type Ia). Moreover, these massive starbursts typically have star-forming companions which are unaccounted for in this tally. We demonstrate a strong correlation between Einstein radius and typical time delays, with cluster lenses often exceeding several months (and therefore most favorable for high-precision H0 inferences). A multivisit monitoring campaign with a sensitive infrared telescope (namely, JWST) is necessary to mitigate dust attenuation. Nevertheless, a porous interstellar medium and clumpy star formation in these extreme galaxies might produce favorable conditions for detecting SNe as transient point sources. Targeted campaigns of known lensed galaxies to discover new lensed SNe can greatly complement wide-area cadenced surveys. Increasing the sample size helps to realize the potential of SN time-delay cosmography to elucidate the Hubble tension through a single-step measurement, independent of other H0 techniques.

Investigating the processes by which galaxies rapidly build up their stellar mass during the peak of their star formation (z = 2–3) is crucial to advancing our understanding of the assembly of large-scale structures. We report the discovery of one of the most gas- and dust-rich protocluster core candidates, PJ0846+15 (J0846), from the Planck All-Sky Survey to Analyze Gravitationally lensed Extreme Starbursts (PASSAGES) sample. The exceedingly high total star formation rate (SFR) uncorrected for lensing magnification ( μ) of μSFR =39900−12900+23000M⊙ yr−1 is the result of a foreground cluster lensing at least 11 dusty star-forming galaxies between z = 2.660 and 2.669, where the intrinsic value is estimated to be SFR =5200−2000+3200M⊙ yr−1. Atacama Large Millimeter/submillimeter Array observations uncovered 18 CO(3–2) emission-line detections, some of which are multiply imaged systems, lensed by a foreground cluster at z = 0.77. We present the first multiwavelength characterization of this field, constructing a lens model that predicts that these 11 galaxies (μ ≃ 1.5–25) are contained within a projected physical extent of 280 × 150 kpc, with a velocity dispersion of σv = 246 ± 72 km s−1. J0846 exhibits the rare case of a protocluster candidate whose core is strongly lensed, offering a magnified view of the rapid stellar buildup within an overdense environment at Cosmic Noon.

Although the James Webb Space Telescope has received much attention for its ability to search deeper into the cosmos than ever before, it also enhances our capability to study objects closer to us in the Universe. We apply a methodology of subtracting intracluster light from the PLCK G165.7+67.0 (G165; z = 0.35) cluster, revealing a population of unresolved pointlike sources including globular clusters (GCs). By applying a fitting algorithm in color space used to select galaxy cluster members, we uncover over 900 GC candidates from our point-source sample. We also identify candidates by estimating the contribution of interlopers to the point-source sample, yielding an estimate of 793 ± 83 GC candidates. We find the color-selected sources to be approximately spatially correlated with the intracluster light and lensing mass of the cluster. The observed luminosity function of the sources shows a turnover point fainter than the completeness limit, so we use fixed-parameter curve-fitting models to predict a k-corrected turnover point in the range −9.4 mag ≤ MF200W ≤ −10.7 mag, although we predict the expected k-corrected turnover point should be closer to −7.7 mag ≤ MF200W ≤ −8.4 mag. We discuss the dynamical state of this disturbed galaxy cluster with a bimodal mass distribution using the spatial distribution of GC candidates and find that the radial profiles of our color-selected GC candidates are very consistent with the lensing-derived surface mass density at >50 kpc.

Ring galaxies are an uncommon class of galaxies whose morphology is closely related to dynamical processes that govern galaxy evolution. Some ring galaxies, known as “collisional ring galaxies,” are thought to form as a consequence of head-on collisions between galaxies, and a number of high-redshift collisional ring galaxies have been discovered and/or studied in the era of the James Webb Space Telescope (JWST). In this paper, we present Hubble Space Telescope Advanced Camera for Surveys, JWST/NIRCam, and JWST/NIRSpec observations of a candidate ring galaxy at zspec = 4.0148, previously identified as a potential gravitational lens. The galaxy exhibits a complex morphology, including three bright clumps along an apparent ring with radius ≈0 .″ 25 ≃ 1.8 kpc. It has a total star formation rate =140−30+20M⊙ yr−1 and log(M*/M⊙)=10.41−0.13+0.11 , making it similar to other high-redshift collisional ring galaxies. Although we argue strongly in favor of the collisional ring explanation, we cannot entirely rule out a galaxy–galaxy strong lensing explanation for the system’s morphology, in which a foreground galaxy at z ≃ 1.7 lenses a galaxy at z ≃ 4.0 into an Einstein ring-like configuration; to confirm the nature of this source, we require kinematic information via high spectral resolution observations. We suggest that current and future gravitational lens surveys should consider high-redshift ring galaxies as possible but significant contaminants.

A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–2 kpc from the host-galaxy nucleus and appears in three different locations as a result of gravitational lensing by G165. These data can yield a value for Hubble’s constant using time delays from this multiply imaged SN Ia that we call “SN H0pe.” Over the cluster, we identified 21 image multiplicities, confirmed five of them using the Near-Infrared Spectrograph, and constructed a new lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014 M ⊙. The photometry uncovered a galaxy overdensity coincident with the SN host galaxy. NIRSpec confirmed six member galaxies, four of which surround the SN host galaxy with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. This compact galaxy group is dominated by the SN host galaxy, which has a stellar mass of (5.0 ± 0.1) × 1011 M ⊙. The group members have specific star formation rates of 2–260 Gyr−1 derived from the Hα-line fluxes corrected for stellar absorption, dust extinction, and slit losses. Another group centered on a strongly lensed dusty star-forming galaxy is at z = 2.24. The total (unobscured and obscured) SFR of this second galaxy group is estimated to be (≳ 100 M ⊙ yr−1), which translates to a supernova rate of ∼1 SNe yr−1, suggesting that regular monitoring of this cluster may yield additional SNe.

In the past decade, submillimeter surveys have been employed to define samples of gravitationally-lensed dusty star-forming galaxies (DSFGs) at z ∼ 1 − 4. These extreme objects () appear to form stars prodigiously at rates of . Using all-sky Planck and WISE surveys, and wide-area Herschel surveys, we have identified the PASSAGES sample, with some of the rarest hyper-luminous IR galaxies ever discovered. We have found that their globally-averaged star formation surface densities are always sub-Eddington, typically by an order of magnitude. This may suggest that our understanding of how radiation pressure from massive stars disrupts the collapse of molecular clouds (thereby quenching star formation) is flawed—or simply that smaller physical resolutions are necessary. With the aid of lensing, we can now capture the source-plane distribution of star formation at ∼ 100pc scales, letting us identify isolated super-Eddington regions where quenching is occurring.

We report the results of James Webb Space Telescope/NIRCam observations of 19 (sub)millimeter sources detected by the Atacama Large Millimeter Array (ALMA). The accurate ALMA positions allowed unambiguous identifications of their NIRCam counterparts. Taking gravitational lensing into account, these represent 16 distinct galaxies in three fields and constitute the largest sample of its kind to date. The counterparts’ spectral energy distributions cover from rest-frame ultraviolet to near-IR and provide photometric redshifts (1 < z < 4.5) and stellar masses (M * > 1010.5 M ⊙), which are similar to submillimeter galaxies (SMGs) studied previously. However, our sample is fainter in (sub)millimeter than the classic SMG samples are, and our sources exhibit a wider range of properties. They have dust-embedded star formation rates as low as 10 M ⊙ yr−1, and the sources populate both the star-forming main sequence and the quiescent categories. The deep NIRCam data allow us to study the rest-frame near-IR morphologies. Excluding two multiply imaged systems and one quasar, the majority of the remaining sources are disk-like and show either little or no disturbance. This suggests that secular growth is a potential route for the assembly of high-mass disk galaxies. While a few objects have large disks, the majority have small disks (median half-mass radius of 1.6 kpc). At this time, it is unclear whether this is due to the prevalence of small disks at these redshifts or some unknown selection effects of deep ALMA observations. A larger sample of ALMA sources with NIRCam observations will be able to address this question.