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1. Mapping Interstellar Dust in the Foreground Outer Disk of Overlapping Galaxy Pair VV 191 with HST and JWST

   https://doi.org/10.3847/1538-3881/adf6aa  

   Robertson, Clayton D; Holwerda, Benne W; Berkheimer, Jessica M; Butrum, Trevor; Castellano, Ian; Cook, Kyle W; Keel, William C; Koekemoer, Anton M; Patel, Divya; del_Carmen_Polletta, Maria; et al (September 2025, The Astronomical Journal)

   Abstract VV 191 is a nearby (z∼ 0.05), overlapping (occulting) galaxy pair, where a multiple-armed spiral galaxy is backlit by an elliptical galaxy. The overlap is used to derive and map dust attenuation in two James Webb Space Telescope NIRCam filters (F090W and F150W) and one visible-band Hubble Space Telescope Wide Field Camera 3 filter (F606W). We present maps of the attenuation in each filter, the ratio of total to selective attenuation with a near-infrared (NIR) color excess, $R_{\widetilde{VI}}$, and the NIR attenuation curve power-law index,α, approximated via Monte Carlo resampling methods. The maps trace the optically thin outer disk of foreground galaxy VV 191b at ∼100 pc physical resolution. We find the distributions of attenuation and $R_{\widetilde{VI}}$to be close to log-normal, and the distribution ofαto be close to Gaussian throughout the disk and in high signal-to-noise ratio areas of VV191b. We analyze three spatially resolved handpicked regions in the far outer disk that are well backlit by the background galaxy. 

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2. ALESS-JWST: Joint (Sub)kiloparsec JWST and ALMA Imaging of z  ~ 3 Submillimeter Galaxies Reveals Heavily Obscured Bulge Formation Events

   https://doi.org/10.3847/1538-4357/ad9a52  

   Hodge, J A; da_Cunha, E; Kendrew, S; Li, J; Smail, I; Westoby, B A; Nayak, O; Swinbank, A M; Chen, C-C; Walter, F; et al (January 2025, The Astrophysical Journal)

   Abstract We present JWST NIRCam imaging targeting 13z ~ 3 infrared-luminous (L_IR ∼ 5 × 10¹²L_⊙) galaxies from the ALESS survey with uniquely deep, high-resolution (0 $\stackrel{\text{″}}{.}$08–0 $\stackrel{″}{.}$16) Atacama Large Millimeter/submillimeter Array 870μm imaging. The 2.0–4.4μm (observed frame) NIRCam imaging reveals the rest-frame near-infrared stellar emission in these submillimeter-selected galaxies at the same (sub)kiloparsec resolution as the 870μm dust continuum. The newly revealed stellar morphologies show striking similarities with the dust continuum morphologies at 870μm, with the centers and position angles agreeing for most sources, clearly illustrating that the spatial offsets reported previously between the 870μm and Hubble Space Telescope morphologies were due to strong differential dust obscuration. The F444W sizes are 78% ± 21% larger than those measured at 870μm, in contrast to recent results from hydrodynamical simulations that predict larger 870μm sizes. We report evidence for significant dust obscuration in F444W for the highest-redshift sources, emphasizing the importance of longer-wavelength MIRI imaging. The majority of the sources show evidence that they are undergoing mergers/interactions, including tidal tails/plumes—some of which are also detected at 870μm. We find a clear correlation between NIRCam colors and 870μm surface brightness on  ∼1 kpc scales, indicating that the galaxies are primarily red due to dust—not stellar age—and we show that the dust structure on  ∼kpc scales is broadly similar to that in nearby galaxies. Finally, we find no strong stellar bars in the rest-frame near-infrared, suggesting the extended bar-like features seen at 870μm are highly obscured and/or gas-dominated structures that are likely early precursors to significant bulge growth. 

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3. Quantifying the Velocity Anisotropy Profile of Galaxy Clusters Using the Uchuu Cosmological Simulation

   https://doi.org/10.3847/1538-4357/adde4b  

   Abdullah, Mohamed H; Mabrouk, Raouf H; Ishiyama, Tomoaki; Wilson, Gillian; Amin, Magdy Y; Khattab, Elamira Hend; Abdel_Rahman, H I (June 2025, The Astrophysical Journal)

   Abstract Galaxy clusters are powerful laboratories for studying both cosmic structure formation and galaxy evolution. We present a comprehensive analysis of the velocity anisotropy profile,β(r), in galaxy clusters using the Uchuu-UniverseMachine mock galaxy catalog, which combines the large-volume UchuuN-body simulation with the UniverseMachine galaxy formation model. Focusing on clusters with $\log M_{200}\ge 13.9\left[h^{-1}{M}_{\odot }\right]$up to redshiftz= 1.5, we investigate the behavior ofβ(r) as a function of clustercentric radius, mass, and redshift. We find thatβ(r) exhibits a universal shape: it rises from isotropic values near the cluster core, peaks at ∼1.7R₂₀₀, declines around 3.4R₂₀₀due to orbital mixing, and increases again in the outskirts, due to the dominance of first-infalling galaxies. Our results show that more massive clusters have higher radial anisotropy and larger peakβvalues. Moreover,β(r) evolves with redshift, with high-redshift clusters displaying more radially dominated orbits and enhanced infall motions. We further derive redshift-dependent power-law scaling relations betweenM₂₀₀and key physical radii—hydrostatic (R_hs), infall ( $R_{\inf }$), and turnaround (R_ta). These findings offer a robust theoretical framework for interpreting the dynamical properties of observed galaxy clusters and provide key insights into the evolution of their dynamical state over cosmic time. 

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4. MSA-3D: Dissecting Galaxies at z ∼ 1 with High Spatial and Spectral Resolution

   https://doi.org/10.3847/1538-4357/ada617  

   Barišić, Ivana; Jones, Tucker; Mortensen, Kris; Nanayakkara, Themiya; Chen, Yuguang; Sanders, Ryan; Bullock, James S; Bundy, Kevin; Faucher-Giguère, Claude-André; Glazebrook, Karl; et al (April 2025, The Astrophysical Journal)

   Abstract Integral field spectroscopy (IFS) is a powerful tool for understanding the formation of galaxies across cosmic history. We present the observing strategy and first results of MSA-3D, a novel JWST program using multi-object spectroscopy in a slit-stepping strategy to produce IFS data cubes. The program observed 43 normal star-forming galaxies at redshifts 0.5 ≲z≲ 1.5, corresponding to the epoch when spiral thin-disk galaxies of the modern Hubble sequence are thought to emerge, obtaining kiloparsec-scale maps of rest-frame optical nebular emission lines with spectral resolutionR≃ 2700. Here we describe the multiplexed slit-stepping method, which is >15 times more efficient than the NIRSpec IFS mode for our program. As an example of the data quality, we present a case study of an individual galaxy atz= 1.104 (stellar massM_*= 10^10.3M_⊙, star formation rate, SFR = 3M_⊙yr⁻¹) with prominent face-on spiral structure. We show that the galaxy exhibits a rotationally supported disk with moderate velocity dispersion ( $\sigma =36_{-4}^{+5}$km s⁻¹), a negative radial metallicity gradient (−0.020 ± 0.002 dex kpc⁻¹), a dust attenuation gradient, and an exponentially decreasing SFR density profile that closely matches the stellar continuum. These properties are characteristic of local spirals, indicating that mature galaxies are in place atz∼ 1. We also describe the customized data reduction and original cube-building software pipelines that we have developed to exploit the powerful slit-stepping technique. Our results demonstrate the ability of JWST slit-stepping to study galaxy populations at intermediate to high redshifts, with data quality similar to current surveys of thez∼ 0.1 Universe. 

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5. SHELLQs-JWST Unveils the Host Galaxies of 12 Quasars at z > 6

   https://doi.org/10.3847/1538-4357/ae045b  

   Ding, Xuheng; Onoue, Masafusa; Silverman, John D; Matsuoka, Yoshiki; Izumi, Takuma; Strauss, Michael A; Yang, Lilan; Jahnke, Knud; Phillips, Camryn L; Treu, Tommaso; et al (October 2025, The Astrophysical Journal)

   Abstract The advent of the James Webb Space Telescope (JWST) has opened new horizons in the study of quasar host galaxies during the reionization epoch (z > 6). Building upon our previous initial measurements of stellar light from two quasar host galaxies at these redshifts, we now report the detection of the stellar light from the full Cycle 1 sample of 12 distant moderate-luminosity quasar (M₁₄₅₀ > −24 mag) host galaxies atz > 6 from the Hyper Suprime-Cam Subaru Strategic Program. Using JWST/NIRCam observations at 1.5 and 3.6μm combined with 2D image decomposition analysis, we successfully detect the host galaxies in 11 of the 12 targets, underscoring the high detection rates achievable with moderate-luminosity quasars. Based on two-band photometry and spectral energy distribution fitting, we find that our host galaxies are massive, with logM_*/M_⊙ = 9.5–11.0. The effective radii range from 0.6 to 3.2 kpc, comparable to the sizes of inactive galaxies with similar masses atz ∼ 6 as measured with imaging from COSMOS-Web. Intriguingly, the two quasar hosts with post-starburst features, which reside at the high-mass end of our sample and exhibit relatively compact morphologies, have similar size and stellar mass surface densities to quiescent galaxies atz ∼ 4–5. These findings suggest that the so-called galaxy compaction scenario is already in place at the reionization epoch, in which gas inflows during starburst phases drive centrally concentrated star formation followed by rapid quenching, bridging the structural transition of massive galaxies from relatively extended star-forming disks to compact quiescent systems. 

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