Masamune Oguri

We present the discovery of a strongly lensed galaxy at z ∼ 11–12, dubbed the “Misty Moons,” identified in the JWST Treasury Survey, Vast Exploration for Nascent, Unexplored Sources. The Misty Moons is gravitationally lensed by the galaxy cluster MACS J0257.1-2325 at z = 0.505, and has five multiple images suggested by two independent lens models. Two of the five images, ID1 and ID2 ( μ ∼ 20–30), are very bright (F200W∼26 AB mag) and exhibit blue SEDs with prominent Ly α breaks. In the source plane, the Misty Moons is a sub- L ^* galaxy ( M _UV ∼ −18.0 mag) resolved into multiple stellar clumps, each of which has an effective radius of r _eff ∼ 10–70 pc and a stellar mass of ∼10 ⁷ M _⊙ . These clumps dominate the stellar mass budget of the Misty Moons (≳80%), similar to other high- z clumps, which suggests a highly clustered mode of star formation in the early Universe, unlike seen in local dwarf galaxies. We convolve the source-plane image with the JWST/NIRCam point-spread function to produce a mock NIRCam image of the Misty Moons without lensing magnification and find that the intrinsic galaxy has a radial surface-brightness profile comparable to those of z ≳ 10 faint galaxies, such as JADES-GS-z13-0 and JADES-GS-z14-1, indicating that the Misty Moons represents a typical z ≳ 10 faint galaxy. The Misty Moons, a lensed galaxy with resolved internal structures, provides an ideal laboratory for exploring the early stages of galaxy formation at z ≳ 10.

Weak lensing surveys require accurate an correction for the point spread function (PSF) when measuring galaxy shapes. For a diffraction-limited PSF, which arises in the context of space-based missions, this correction depends on each galaxy’s spectral energy distribution (SED). Therefore, sufficiently accurate knowledge of the SED is needed for every galaxy. In the Euclid mission, galaxy SED reconstruction, which is one of the tasks of the photometric-redshift processing function (PHZ PF), relies on broad- and medium-band ancillary photometry. The limited wavelength sampling of the I _E passband and signal-to-noise ratio might affect the reconstruction accuracy and translate into biases in the weak lensing measurements. In this study, we present the methodology employed in the Euclid PHZ PF for reconstructing galaxy SEDs at 55 wavelengths, sampling the I _E passband every 10 nm, and we assess whether it fulfils the accuracy requirements imposed on the Euclid PSF model. We employed both physics- and data-driven methods, focussing on a new approach of template-based flux correction and Gaussian processes. For validation, we introduced an SED metric whose bias translates into inaccuracies in the PSF quadrupole moments. Our findings demonstrate that Gaussian processes and template fitting meet the requirements only in specific, but complementary redshift intervals. We therefore propose a hybrid approach that leverages both methods. This solution proves effective in meeting the Euclid accuracy requirements for most of the redshift range of the survey. Finally, we investigated the impact on the SED reconstruction of a new set of 16 evenly-spaced medium-band filters for the Subaru telescope, providing quasi-spectroscopic coverage of the I _E passband. This study offers promising results, ensuring accurate SED reconstruction and meeting the mission PSF requirements. This work thus provides not only the methodological foundation of galaxy SED reconstruction in the Euclid PHZ PF, but also a roadmap for future improvements using a new medium-band survey.

The multiply imaged SN 2022riv was discovered through a search of galaxy cluster fields as part of a Hubble Space Telescope (HST) SNAP program to find highly magnified stars. The supernova (SN) was detected in the image corresponding to the longest time delay of a galaxy at redshift z = 1.522, strongly lensed by the foreground galaxy cluster RX J2129.7+0005. Follow up James Webb Space Telescope (JWST) NIRSpec G140M and PRISM spectroscopy yields an SN Ia classification. Using the SALT3-NIR light-curve fitter, we obtain a cosmology-independent measurement of the magnification of 5.35 ± 1.01 for the last-to-arrive image of the SN, with multiple SALT SN spectral time-series models yielding consistent constraints. The last-to-arrive image of SN 2022riv we detect appeared adjacent to the brightest cluster galaxy (BCG) at a location with an exceptionally high stellar mass density (∼1–2 dex higher than that of SN Refsdal), where microlensing is expected to introduce a 20%–50% modulation of the magnification. Analyzing six independent lens models of the cluster, we find that four predict the magnification with much greater precision ( p < 0.05) than would be expected by random chance, given the large effect anticipated from microlensing. Five models yield magnifications of roughly 4–7 (within 1 σ ) prior to accounting for microlensing, whereas HoliGRALE favors a significantly higher value of 15.39 ± 0.85. After incorporating nominal microlensing, the HoliGRALE prediction is within 1 σ tension with our measurement. A companion paper will present constraints on the relative time delay of the image that arrived earlier.

We present a parametric strong-lensing model for the galaxy cluster MACS J1931.8-2635 ( z _l = 0.35), accompanying the detection of the spectroscopically confirmed SN Eos at z = 5.13. We identify 10 new multiple-image systems in recent VENUS JWST/NIRCam imaging, so that the model is constrained with a total of 19 robust multiple-image systems—nine of which also have a spectroscopic redshift. For the point-like source corresponding to SN Eos, our model predicts a total of five images, with the observed radial image pair having a similar magnification of μ ≃ 25–30 and a small time delay of . ″ 44. We present the lens-modeling results, including newly identified systems such as a triply imaged, grand-design spiral galaxy candidate at z ≃ 3.6 5 − 0.09 + 0.04 , and discuss the potential of using high-redshift lensed SNe for cosmography.

Recent high-resolution imaging observations of strong lens systems reveal dense low-mass perturbers. We propose a soliton core, whose central density is boosted by a supermassive black hole (SMBH), in the fuzzy dark matter (FDM) model as an efficient perturber in strong gravitational lensing. The higher central density makes it less efficient in the tidal mass loss, and leads to the higher impact in gravitational lensing. We show that the mass profile of a ∼10 ⁶ M _⊙ perturber in JVAS B1938+666, which does not resemble any known astronomical object, can be well explained by a soliton core in the FDM model with the mass of 4 × 10 ^-21 eV hosting an SMBH with the mass of 4 × 10 ⁵ M _⊙ . The high mass of the SMBH may be explained by several scenarios that predict heavy SMBH seeds such as the direct collapse black hole formation and primordial black holes.

We present the first catalogue of strong-lensing galaxy clusters identified in the Euclid Quick Release 1 observations (covering 63.1 deg ² ). This catalogue is the result of the visual inspection of 1260 Euclid image cutouts of previously identified galaxy clusters. Each galaxy cluster was assigned a lensing score, 𝒫 _lens , derived from the aggregated votes of multiple visual inspectors, the majority of whom possess extensive expertise in strong gravitational lensing. Votes were assigned based on the assessed credibility and plausibility of the identified strong-lensing features. Specifically, we identified 83 gravitational lenses with 𝒫 _lens > 0.5, of which 14 have 𝒫 _lens = 1 and clearly exhibit secure strong-lensing features, such as giant tangential and radial arcs, and multiple images. Considering the measured number density of lensing galaxy clusters, approximately 0.3 deg ⁻² for 𝒫 _lens > 0.9, we predict that Euclid will likely observe more than 4500 strong-lensing clusters over the course of the mission. Notably, only three of the identified cluster-scale lenses had previously been observed from space. Thus, Euclid has provided the first high-resolution imaging for the remaining 80 strong-lensing galaxy cluster candidates, including those with the highest scores. The identified strong-lensing features will be used to train deep-learning models to automatically identify gravitational arcs and multiple images in the Euclid observations. This study confirms the great potential of Euclid for finding new strong-lensing clusters, enabling exciting new discoveries on the nature of dark matter and dark energy and the study of the high-redshift Universe.

We present a catalog of 57 high-redshift z > 6 galaxy candidates, including 14 spectroscopic confirmations ( z = 6.10–9.25), 2 little red dots ( z = 4.77, 5.81), and 2 interlopers ( z = 3.23, 3.72), based on JWST NIRCam imaging (seven filters), NIRSpec spectroscopy (PRISM and G395H), and archival HST imaging (17 filters) of the strong lensing galaxy cluster MACS0647. Our highest redshift confirmation ( z = 9.25) is an extremely blue galaxy, and here we identify a spectral turnover likely due to damped Ly α . We identify an overdensity of galaxies with spectroscopic redshifts z = 6.1, confirming the z ∼ 6 overdensity identified in HST images. In one of these galaxies, our high-resolution G395H spectroscopy reveals two spatially resolved components with a velocity difference of ∼90 km s ⁻¹ ; if these components are gravitationally bound, this would imply a dynamical mass on the order of ∼10 ⁸ M _⊙ given their projected separation. We present spectral line fluxes, widths, and derived physical properties, including stellar masses (10 ⁸ –10 ⁹ M _⊙ ) and metallicities (10%–40% Z _⊙ ) for our spectroscopic sample. We note half of our NIRSpec data was obtained with standard three-slitlet nods and half was obtained with single slitlets yielding similar results, demonstrating the power to observe more sources on a densely packed NIRSpec microshutter assembly.

Context. This is the second paper in a series exploring the X-ray properties of galaxy clusters optically selected by the Subaru Hyper Suprime-Cam (HSC) survey, using data from the SRG/eROSITA Final Equatorial-Depth Survey (eFEDS). Aims. We aim to investigate scaling relations between observable cluster properties and mass and to study the radial X-ray profiles of a large sample of optically selected clusters. Methods. We analyzed a sample of 997 CAMIRA clusters with a richness of N > 15 and redshifts of 0.1 < z < 1.3. Using bolometric luminosities derived from count rates and a weak-lensing mass calibration, we studied the L − M and N − M scaling relations through stacking analysis, while accounting for selection effects and redshift evolution. We also compared clusters with and without X-ray counterparts in the eFEDS catalog in terms of their scaling relations and surface-brightness profiles. Results. The best-fit L − M slope (1.56 ^+0.14 _−0.12 ) is slightly steeper than the self-similar prediction, yet it remains consistent with our previous findings. The N − M slope (0.766 ^+0.070 _−0.060 ) broadly agrees with theoretical expectations and other optical samples. The data do not require any additional redshift evolution beyond the standard self-similar scaling, although current constraints on evolution remain weak. X-ray-detected clusters exhibit a marginally steeper L − M slope, higher central surface brightness, and more centrally concentrated X-ray profiles than undetected systems. Conclusions. Our results highlight systematic differences in the X-ray properties between optically and X-ray-selected cluster samples. This study extends scaling relation analyses into lower mass and luminosity regimes, demonstrating the value of combining deep X-ray and optical surveys such as eROSITA and Subaru HSC.

We present results of new observations of [O i ] 145 μ m and [N ii ] 205 μ 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 μ m and dust continua. Using the Atacama Large Millimeter/submillimeter Array, we successfully detect [O i ] 145 μ m emission from all targets at >4 σ significance. However, [N ii ] 205 μ m emission is undetected in all galaxies (signal-to-noise ratio < 3.5 σ ) except for a tentative detection from A1689-zD1. From the observed high [C ii ]/[N ii ] emission line ratios (≳20−80), we find that most of the [C ii ] 158 μ m emission arises from neutral gas regions (3 σ lower limits of ≳74%−96%). From [O i ] 145 μ m, [C ii ] 158 μ 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 ∼ 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 μ m emission lines and the oxygen abundances measured from recent JWST observations. We find gas mass ratios of f _gas ∼ 0.3–0.8, which are similar to earlier studies using [C ii ] 158 μ m. Starting from this pilot observation, future large [O i ] 145 μ m emission line surveys will provide us with currently little-known neutral gas properties of star-forming galaxies in the early Universe.

Supermassive black holes and their host galaxies grow together over time, producing correlations between the black hole mass and various galaxy properties. Determining the evolution of these correlations requires precise measurements of the masses of distant black holes. We observed the gravitationally lensed quiescent galaxy MRG-M0138 at redshift 1.95 using James Webb Space Telescope integral field spectroscopy to spatially resolve the kinematics of stars within the black hole’s sphere of influence. By using a foreground lens model and fitting stellar dynamical models, we determined the mass of its inactive black hole to be M • = 6.0 − 1.7 + 2.1 × 10 9 solar masses. Comparing this measurement to local galaxies, we found that M • is higher than expected given the galaxy’s bulge mass but consistent with the correlation of M • with stellar velocity dispersion.