Context. One of the most remarkable and unexpected results of the James Webb Space Telescope is the discovery of a population of compact red galaxies: the so-called little red dots (LRDs). The existence of these galaxies raises many questions, including that of their nature and origin, as well as that of their evolution. Indeed, these compact red sources exhibit a pronounced decline in number density by nearly two orders of magnitude from z = 6 to z = 3. Aims. In this paper, we investigate the possible evolution of this galaxy population at a lower redshift. To this end, we have identified a sample of candidates in the CEERS images that could represent the descendants of LRDs by assuming a single evolutionary path: the development of a blue star-forming outskirt while retaining a inner red core. Methods. Our color–magnitude selection identifies red galaxies as red as LRDs at z < 4, defined by a compact, red, inner region and blue outskirts. The red core is associated with the LRD population, while the blue periphery traces recently formed young stars. Morphological properties were derived by fitting single Sérsic profiles, while other physical quantities were obtained through spectral energy distribution (SED) fitting, assuming a stellar-only model for both the inner region and the outskirts. Results. The selected galaxies are likely “post-LRDs” galaxies, showing similar properties to LRDs under a stellar-only model: stellar masses of M* ≈ 1010 M⊙, central densities Σ* ≈ 1011 M⊙ kpc−2, similar rest-frame red colors, and a ∼1 kpc offset below the size–mass relation. Their number density at z = 3 ± 0.5 (10−4.15 Mpc−3) matches that of LRDs at 5 < z < 7, supporting an evolutionary connection. We find a strong redshift-dependent increase in both outskirts’ mass fraction and galaxy size, from ∼250 pc at z = 5 to ∼600 pc at z = 3, indicating overall stellar growth. Meanwhile, the core remains as red and as massive, but the characteristic V shaped SED fades as the extended star-forming envelope becomes dominant. Conclusions. These findings support an evolutionary scenario in which LRDs gradually acquire an extended stellar component over cosmic time by cold accretion. This growth affects the initial LRD state in two key ways: the physical size increases and the characteristic V shaped SED in the core becomes less distinct and disappears. As a result, the original selection criteria based on both of them can no longer identify this population as it evolves, providing an explanation for their observed decline in number density.

Galaxy mergers, with their high sensitivity to initial conditions, provide a valuable setting for comparative studies of galaxy simulation codes. Following our first paper focusing on merger-driven star formation, we present a code comparison examining the morphological transformation impact of a major galaxy merger at z ≈ 4.5 on a Milky Way-mass galaxy progenitor. Our analysis employs nine state-of-the-art codes from the AGORA CosmoRun cosmological zoom-in simulation suite. For this merger, we show that the adopted stellar feedback type influences the galaxy's compaction and stellar disc formation. Codes with purely thermal feedback produce a merger remnant that forms a disc and becomes compact primarily during and after coalescence; codes that include kinetic feedback begin disc formation and compaction around the first periapsis; and codes with strong delayed cooling or superbubble feedback suppress disc formation and produce a more extended remnant. In contrast, the orientation of the remnant disc is code-independent. In all codes, the rotational angular momentum of the remnant disc aligns with the interaction's orbital angular momentum rather than the pre-merger rotational axis, implying that the infalling gas preserves its orbital angular momentum to form a new disc. Comparisons with the Santa Cruz semi-analytic model show reasonable agreement in stellar mass and half-mass radius, yet the model underpredicts (overpredicts) the dark matter fraction and velocity dispersion for codes exhibiting strong compaction (expansion). The systematic dependence of our remnants' morphology on feedback schemes demonstrates that merger remnant morphology may serve as a powerful probe of stellar feedback processes.

We investigate the rest-frame optical size-stellar mass relation of galaxies at 0.5 < z < 6.0 using deep JWST/NIRCam and MIRI imaging from the PRIMER survey. We find that star-forming galaxies (SFGs) exhibit a broken power-law relation at all redshifts, with a nearly constant pivot mass (M-p) of similar to 10(10)M(circle dot) and a slope flattening above M-p. This highlights the prevalence of a population of compact, massive SFGs that was underrepresented in previous studies. The size distribution of quiescent galaxies (QGs) is well described by a mixture power-law model, with a pivot mass that increases from M-p similar to 10(10.0)M(circle dot )at z = 0.75 to M-p similar to 10(10.5)M(circle dot) at z = 2.6, suggesting that the minimum halo mass required to quench high-mass galaxies increases with redshift. The bending in the size-mass relation of SFGs supports two distinct size growth modes. At M-star < M-p, size growth is closely coupled to halo growth, while at M-star > M-p, an increasing fraction of SFGs decouple from halo growth and become compact, likely associated with rapid bulge (and black hole) growth in M-h greater than or similar to 10(12)M(circle dot )halos. These compact SFGs are promising progenitors of massive QGs, as evidenced by their similar masses, surface brightness profiles, and morphologies. Their high number densities can account for the observed buildup of massive QGs at z > 2, suggesting that the compaction pathway, rather than major mergers of extended SFGs, dominates the formation of high-z massive QGs.

Given their highly nonlinear dynamics and sensitivity to initial conditions, galaxy mergers are a compelling area to conduct a simulation code comparison. We perform a comparative study of a major galaxy merger at z ≈ 4.5 in cosmological zoom-in hydrodynamic simulations of a Milky Way-mass galaxy progenitor. The comparison employs the AGORA CosmoRun suite of nine well-calibrated, state-of-the-art numerical codes, each adopting a different stellar feedback scheme. We find that the evolution of the star formation rate (SFR) during the interaction is strongly shaped by the stellar feedback type. Using kinetic feedback in the feedback model drives a pronounced merger-induced starburst that starts to subside before coalescence; using thermal feedback without kinetic feedback yields prolonged SFR growth even after coalescence; and using delayed cooling or radiation pressure results in highly fluctuating SFR. Tracking gas particles in particle-based codes reveals that kinetic feedback facilitates gas inflow from the secondary galaxy onto the primary galaxy between the first periapsis and apoapsis, thus producing an earlier and more prominent starburst. In contrast, thermal feedback, augmented by superbubble or delayed-cooling feedback, suppresses gas cooling, creates a more extended gas distribution, and hinders strong starbursts during the merger. We also observe an inverse correlation between burst fraction and pre-merger gas fraction that is independent of feedback models. Overall, these results highlight the sensitivity of simulated galaxy mergers' star formation response to stellar feedback prescriptions. This study indicates that galaxy mergers may serve as a good testbed for stellar feedback processes in cosmological simulations.

We investigate the rest-frame optical size-stellar mass relation of galaxies at 0.5 M_ p, an increasing fraction of SFGs decouple from halo growth and become compact, likely associated with rapid bulge (and black hole) growth in M_ h≳ 10^12 M_⊙ halos. These compact SFGs are promising progenitors of massive QGs, as evidenced by their similar masses, surface brightness profiles, and morphologies. Their high number densities can account for the observed buildup of massive QGs at z > 2, suggesting that the compaction pathway, rather than major mergers of extended SFGs, dominates the formation of high-z massive QGs.

Dynamical friction governs the orbital decay of massive perturbers within galaxies and dark matter halos, yet its standard Chandrasekhar formulation fails in systems with cores of (roughly) constant density, where inspiral can halt or even reverse, phenomena known respectively as core stalling and dynamical buoyancy. Although these effects have been observed in simulations, the conditions under which they arise remain unclear. Using high-resolution N-body simulations and analytic insights from kinetic theory, we systematically explore the physical origin of these effects. We demonstrate that the overall distribution function (DF) of the host, not just its central density gradient, determines the efficiency and direction of dynamical friction. Core stalling arises when the perturber encounters a plateau in the DF, either pre-existing or dynamically created through its own inspiral, while buoyancy emerges in systems whose DFs possess an inflection that drives an unstable dipole mode. We show that double power-law density profiles with rapid outer-to-inner slope transitions naturally produce such DF features, which is why structurally similar cores can yield radically different dynamical outcomes. Our results provide a unified framework linking the phase-space structure of galaxies to the fate of embedded massive objects, with direct implications for off-center AGN, the dynamics of nuclear star clusters, and the stalled coalescence of black holes in dwarf galaxies and massive ellipticals.

Context. One of the most remarkable and unexpected results of the James Webb Space Telescope is the discovery of a population of compact red galaxies: the so-called little red dots (LRDs). The existence of these galaxies raises many questions, including that of their nature and origin, as well as that of their evolution. Indeed, these compact red sources exhibit a pronounced decline in number density by nearly two orders of magnitude from z = 6 to z = 3. Aims. In this paper, we investigate the possible evolution of this galaxy population at a lower redshift. To this end, we have identified a sample of candidates in the CEERS images that could represent the descendants of LRDs by assuming a single evolutionary path: the development of a blue star-forming outskirt while retaining a inner red core. Methods. Our color–magnitude selection identifies red galaxies as red as LRDs at z < 4, defined by a compact, red, inner region and blue outskirts. The red core is associated with the LRD population, while the blue periphery traces recently formed young stars. Morphological properties were derived by fitting single Sérsic profiles, while other physical quantities were obtained through spectral energy distribution (SED) fitting, assuming a stellar-only model for both the inner region and the outskirts. Results. The selected galaxies are likely “post-LRDs” galaxies, showing similar properties to LRDs under a stellar-only model: stellar masses of M* ≈ 1010 M⊙, central densities Σ* ≈ 1011 M⊙ kpc−2, similar rest-frame red colors, and a ∼1 kpc offset below the size–mass relation. Their number density at z = 3 ± 0.5 (10−4.15 Mpc−3) matches that of LRDs at 5 < z < 7, supporting an evolutionary connection. We find a strong redshift-dependent increase in both outskirts’ mass fraction and galaxy size, from ∼250 pc at z = 5 to ∼600 pc at z = 3, indicating overall stellar growth. Meanwhile, the core remains as red and as massive, but the characteristic V shaped SED fades as the extended star-forming envelope becomes dominant. Conclusions. These findings support an evolutionary scenario in which LRDs gradually acquire an extended stellar component over cosmic time by cold accretion. This growth affects the initial LRD state in two key ways: the physical size increases and the characteristic V shaped SED in the core becomes less distinct and disappears. As a result, the original selection criteria based on both of them can no longer identify this population as it evolves, providing an explanation for their observed decline in number density.

We investigate how galactic disk structures connect to the detailed properties of their host dark-matter halos using the TNG50 simulation. From the hydrodynamic and matched dark-matter-only runs, we measure a comprehensive list of halo properties describing density structure, angular momentum, shape, assembly history, and environment. Using the morphological decomposition developed in Paper I, we quantify the sizes, scale heights, and mass fractions of the disk components for galaxies at 0 <= z <= 4. A random forest regression shows that halo properties alone predict disk size and thickness with high accuracy, while a symbolic regression (SR) provides compact empirical relations with slightly lower accuracy. Disk height is consistently easier to predict than disk size, and lower-mass halos yield higher accuracy than massive halos. Predictions based on halo properties measured in the hydro simulations outperform those based on halos matched in the dark-matter-only simulation, reflecting the imprint of baryonic restructuring on the inner halo. The SHAP analysis reveals the most informative halo parameters include concentration, Einasto shape, global and inner spin, and recent mass accretion, although their importance varies across disk properties. We show correlations between disk size and the density-profile shape arise primarily from a disk-induced modification of the inner halo, rather than a primordial connection. Finally, we point out that disks become more extended with respect to their host halos at higher redshift in low-mass halos, while massive high-redshift halos show the opposite trend. We provide SR-based prescriptions that accurately map halo properties to disk structures, offering practical tools for galaxy-halo modeling.

We perform a cosmological zoom-in simulation of a massive galaxy (M_s∼10^10 M_⊙ at z∼10) using the GIZMO code. By employing ≤ 3 pc resolution and a 3.4 Myr supernova feedback delay, we capture the feedback-free starbursts (FFB) in clusters. The simulation reproduces FFB model predictions and super-bright galaxies observed by JWST. At z∼10, cold streams feed a compact galaxy (R_ e∼1 kpc), with stellar and surface densities (>10^5 cm^-3, >10^5 M_⊙ pc^-2) exceeding FFB thresholds. The global star-formation efficiency (SFE) is ε_s∼0.2–0.3, associated with a fluctuating star-formation history. We identified over 10^5 star clusters (M_⋆>10^4.5 M_⊙) with a nearly scale-free mass distribution (dN/ dlog M∝ M^-1.06). Approximately 90% of star formation occurs in clusters, which at a given time constitute 30–40% of the total stellar mass. The star formation in most of the clusters of masses <10^7 M_⊙, occurs in bursts of <3 Myr and a local SFE ∼0.5± 0.2. Cluster metallicities (-2.01<log (Z/Z_⊙)<-0.45) indicate rapid baryon recycling. Feedback-driven outflows exhibit typical temperature of 10^7 K and typical velocities of ∼ 2000 km s^-1. In the highly dynamic central 1 kpc, clusters undergo rapid orbital decay and merge to assemble the oblate nuclear stellar cluster. Cluster shapes range from oblate to prolate, with a triaxial median. These clusters are consistent with JWST observations, and a fraction of them may survive to yield the globular clusters (GCs) at low redshifts.

JWST has identified a large population of faint, broad-line active galactic nuclei (AGN) in the early universe that are powered by black holes (BHs) that often appear overmassive relative to their host galaxies. In this study, we examine the relationship between BH mass and galaxy stellar mass at 33σ above the relationship measured for local broad-line AGN. We derive an intrinsic scatter in this relationship of 0.9 dex, which does not vary over the redshift range of our sample. We also find that the M_ BH/M_⋆ ratio increases by 2.3 dex from z = 3.5 and z = 6.5 with a confidence level of > 3σ. We attribute this trend with the increasing fraction of LRDs in our sample at z>4 as their host masses are ∼1 dex lower than the non-LRD AGN in our sample. These results support a picture in which the BHs powering JWST's broad-line AGN are genuinely overmassive and become increasingly so with redshift. We discuss the implications of our findings on early BH growth relative to that of their host galaxies and the constraints it places on BH seeding models.

Aims. We study the radial transport of cold gas within simulated disk galaxies at cosmic noon. Our aim is to determine whether disk instability or accretion along cold streams from the cosmic web is the driving mechanism behind the transport. Methods. Disks were selected based on kinematics and flattening from the VELA zoom-in hydro-cosmological simulations. We mapped the radial velocity fields in the disks, computed their averages as a function of radius and over the whole disk, and obtained the radial mass flux in each disk as a function of radius. The transport directly associated with fresh incoming streams was identified by selecting cold gas cells that are either on incoming streamlines or have a low metallicity. Results. We find the radial velocity fields in VELA disks to be highly non-axisymmetric, showing both inflows and outflows. However, in most cases, the average radial velocities, both as a function of radius and over the whole disk, were directed inward, with the disk-averaged radial velocities typically amounting to a few percent of the disk-averaged rotational velocities. This is significantly lower than the expectations from various models that analytically predict the inward mass transport to be driven by torques associated with disk instability. Under certain simplifying assumptions, such models typically predict average inflows of more than 10% of the rotational velocities. Analyzing the radial motions of streams and off-stream material, we find that the radial inflow in VELA disks is dominated by the stream inflows themselves, especially in the outer disks. Conclusions. The high inward radial velocities inferred in observed disks at cosmic noon at the level of similar to 20% of the rotational velocities may reflect motions along inflowing streams from the cosmic web rather than being generated by disk instability.

Motivated by the early excess of bright galaxies seen by JWST, we run zoom-in cosmological simulations of a massive galaxy at Cosmic Dawn, in a halo of 10(11)M(circle dot) at z = 9, using the hydro-gravitational code RAMSES at an effective resolution similar to 10 pc . We investigate physical mechanisms that enhance the star formation efficiencies (SFEs) at the high gas densities of the star-forming regions in this galaxy (similar to 3 x 10(3) cm(-3), similar to 10(4) M-circle dot pc(-2)). Our fiducial star formation recipe uses a physically motivated, turbulence-based, multi-freefall model, avoiding ad hoc extrapolation from lower redshifts. By z = 9, our simulated galaxy is a clumpy, thick, rotating disc with a high stellar mass similar to 3 x 10(9) M-circle dot and high star formation rate similar to 50 M-circle dot yr(-1). The high gas density makes supernova (SN) feedback less efficient, producing a high local SFE greater than or similar to 10 per cent . The global SFE is set by feedback-driven outflows and only weakly correlated with the local SFE. Photoionization heating makes SN feedback more efficient, but the integrated SFE always remains high. Intense accretion at Cosmic Dawn seeds turbulence that reduces local SFE, but this only weakly affects the global SFE. The star formation histories of our simulated galaxies are similar to observed massive galaxies at Cosmic Dawn, despite our limited resolution. We set the stage for future simulations which treat radiation self-consistently and use a higher effective resolution similar to 1 pc that captures the physics of star-forming clouds.

We address the formation of giant clumps in violently unstable gas-rich disc galaxies at cosmic noon. While these are commonly thought to originate from gravitational Toomre instability, some cosmological simulations have indicated that clumps can form in Lagrangian proto-clump regions where the Toomre Q parameter is well above unity, which are linearly stable. Examining one of these cosmological simulations, we find that it exhibits an excess in compressive modes of turbulence with converging motions. The energy in converging motions within proto-clumps is similar to 70 per cent of the total turbulent energy, compared to similar to 17 per cent expected in equipartition. When averaged over the whole disc, similar to 40 per cent of the turbulent energy is in compressive modes, mostly in converging motions, with the rest in solenoidal modes, compared to the (1/3) - (2/3) division expected in equipartition. By contrast, we find that in an isolated-disc simulation with similar properties, resembling high-z star-forming galaxies, the different turbulence modes are in equipartition, both in proto-clumps and over the whole disc. We conclude that the origin of excessive converging motions in proto-clumps is external to the disc, and propose several mechanisms that can induce them. This is an additional mechanism for clump formation, complementary to and possibly preceding gravitational instability.

Aims. The scenario of feedback-free starbursts (FFB), which predicts excessively bright galaxies at cosmic dawn as observed using JWST, may provide a natural setting for black hole (BH) growth. This involves the formation of intermediate-mass seed BHs and their runaway mergers into super-massive BHs with high BH-to-stellar mass ratios and low Active Galactic Nucleus (AGN) luminosities. Methods. We present a scenario of merger-driven BH growth in FFB galaxies and study its feasibility. Results. Black hole seeds form within the building blocks of the FFB galaxies, namely, thousands of compact star clusters, each starbursting in a free-fall time of a few million years before the onset of stellar and supernova feedback. The BH seeds form by rapid core collapse in the FFB clusters, in a few free-fall times, which is sped up by the migration of massive stars due to the young, broad stellar mass function and stimulated by a "gravo-gyro" instability due to internal cluster rotation and flattening. BHs of similar to 10(4) M-circle dot are expected in similar to 10(6) M-circle dot FFB clusters within sub-kiloparsec galactic disks at z similar to 10. The BHs then migrate to the galaxy center by dynamical friction, hastened by the compact FFB stellar galactic disk configuration. Efficient mergers of the BH seeds will produce similar to 10(6 - 8) M-circle dot BHs with a BH-to-stellar mass ratio similar to 0.01 by z similar to 4 - 7, as observed. The growth of the central BH by mergers can overcome the bottleneck introduced by gravitational wave recoils if the BHs inspiral within a relatively cold disk or if the escape velocity from the galaxy is boosted by a wet compaction event. Such events, common in massive galaxies at high redshifts, can also help by speeding up the inward BH migration and by providing central gas to assist with the final parsec problem. Conclusions. The cold disk version of the FFB scenario provides a feasible route for the formation of supermassive BHs.

Theory and observations reveal that the circumgalactic medium (CGM) and the cosmic web at high redshifts are multiphase, with small clouds of cold gas embedded in a hot, diffuse medium. We study the 'shattering' of large, thermally unstable clouds into tiny cloudlets of size pound shatter min(cst cool ) using idealized numerical simulations. We expand upon previous works by exploring the effects of cloud geometry (spheres, streams, and sheets), metallicity, and an ionizing ultraviolet background. We find that 'shattering' is mainly triggered by clouds losing sonic contact and rapidly imploding, leading to a reflected shock that causes the cloud to re-expand and induces Richtmyer-Meshkov instabilities at its interface. The fragmented cloudlets experience a drag force from the surrounding hot gas, leading to recoagulation into larger clouds. We distinguish between 'fast' and 'slow' coagulation regimes. Sheets are always in the 'fast' coagulation regime, while streams and spheres transition to 'slow' coagulation above a critical overdensity, which is smallest for spheres. Surprisingly, ( pound shatter) does not appear to be a characteristic clump size even if it is well resolved. Rather, fragmentation continues until the grid scale with a mass distribution of N( > m ) oc m(- 1) . We apply our results to cold streams feeding massive (Mv > 10 (12) M- (R) ) galaxies at z > 2 from the cosmic web, finding that streams likely shatter upon entering the hot CGM through the virial shock. This could explain the large clumping factors and covering fractions of cold gas around such galaxies, and may be related to galaxy quenching by preventing cold streams from reaching the central galaxy.

Context. Satellite galaxies experience multiple physical processes when interacting with their host halos, often leading to the quenching of star formation. In the Local Group, satellite quenching has been shown to be highly efficient, affecting nearly all satellites except the most massive ones. While recent surveys study Milky Way-analogs to assess how representative our Local Group is, the dominant physical mechanisms behind satellite quenching in Milky Way-mass halos remain under debate. Aims. We analyze satellite quenching within the same Milky Way-mass halo simulated using various widely used astrophysical codes, each using different hydrodynamic methods and implementing different supernovae feedback recipes. The goal is to determine whether quenched fractions, quenching timescales, and the dominant quenching mechanisms are consistent across codes or if they show sensitivity to the specific hydrodynamic method and supernovae feedback physics employed. Methods. We used a subset of high-resolution cosmological zoom-in simulations of a Milky Way-mass halo from the multiple-code AGORA CosmoRun suite. Our analysis focuses on comparing satellite quenching across the different models and against observational data. We also analyzed the dominant mechanisms driving satellite quenching in each model. Results. We find that the quenched fraction is consistent with the latest SAGA Survey results within its 1σ host-to-host scatter across all the models. Regarding quenching timescales, all the models reproduce the trend observed in the ELVES survey, Local Group observations, and previous simulations: The less massive the satellite, the shorter its quenching timescale. All of our models converge on the dominant quenching mechanisms: Strangulation halts cold gas accretion in all satellites, while ram pressure stripping is the predominant mechanism for gas removal, and it is particularly effective in satellites with M*<108 M⊙. Nevertheless, the efficiency of the stripping mechanisms differs among the codes, showing a strong sensitivity to the different supernovae feedback implementations and/or hydrodynamic methods employed.

Context. Satellite galaxies experience multiple physical processes when interacting with their host halos, often leading to the quenching of star formation. In the Local Group, satellite quenching has been shown to be highly efficient, affecting nearly all satellites except the most massive ones. While recent surveys study Milky Way-analogs to assess how representative our Local Group is, the dominant physical mechanisms behind satellite quenching in Milky Way-mass halos remain under debate. Aims. We analyze satellite quenching within the same Milky Way-mass halo simulated using various widely used astrophysical codes, each using different hydrodynamic methods and implementing different supernovae feedback recipes. The goal is to determine whether quenched fractions, quenching timescales, and the dominant quenching mechanisms are consistent across codes or if they show sensitivity to the specific hydrodynamic method and supernovae feedback physics employed. Methods. We used a subset of high-resolution cosmological zoom-in simulations of a Milky Way-mass halo from the multiple-code AGORA CosmoRun suite. Our analysis focuses on comparing satellite quenching across the different models and against observational data. We also analyzed the dominant mechanisms driving satellite quenching in each model. Results. We find that the quenched fraction is consistent with the latest SAGA Survey results within its 1 sigma host-to-host scatter across all the models. Regarding quenching timescales, all the models reproduce the trend observed in the ELVES survey, Local Group observations, and previous simulations: The less massive the satellite, the shorter its quenching timescale. All of our models converge on the dominant quenching mechanisms: Strangulation halts cold gas accretion in all satellites, while ram pressure stripping is the predominant mechanism for gas removal, and it is particularly effective in satellites with M-*<10(8) M-circle dot. Nevertheless, the efficiency of the stripping mechanisms differs among the codes, showing a strong sensitivity to the different supernovae feedback implementations and/or hydrodynamic methods employed.

We investigate how differences in the stellar feedback produce disks with different morphologies in Milky Way–like progenitors over 1 ≤ z ≤ 5, using eight state-of-the-art cosmological hydrodynamics simulation codes in the AGORA project. In three of the participating codes, a distinct, rotation-dominated inner core emerges with a formation timescale of ≲300 Myr, largely driven by a major merger event, while two other codes exhibit similar signs of wet compaction—gaseous shrinkage into a compact starburst phase—at earlier epochs. The remaining three codes show only weak evidence of wet compaction. Consequently, we divide the simulated galaxies into two groups: those with strong compaction signatures and those with weaker ones. Galaxies in these two groups differ in size, stellar age gradients, and disk-to-total mass ratios. Specifically, codes with strong wet compaction build their outer disks in an inside-out fashion, leading to negative age gradients, whereas codes with weaker compaction feature flat or positive age gradients caused primarily by outward stellar migration. Although the stellar half-mass radii of these two groups diverge at z ∼ 3, the inclusion of dust extinction brings their sizes and shapes in mock observations closer to each other and to observed galaxies. We attribute the observed morphological differences primarily to variations in the stellar feedback implementations—such as delayed cooling timescales, and feedback strengths—that regulate both the onset and duration of compaction. Overall, our results suggest that disk assembly at high redshifts is highly sensitive to the details of the stellar feedback prescriptions in simulations.

We present the mass-metallicity relation (MZR) for a parent sample of 604 galaxies at z = 5.34-6.94 with [O III] doublets detected that was obtained from the deep JWST/NIRCam wide field slitless spectroscopic (WFSS) observations in 26 quasar fields. The sample incorporates the full observations of 25 quasar fields from the JWST Cycle 1 GO program ASPIRE and the quasar SDSS J0100+2802 from the JWST EIGER program. We identified 204 galaxies residing in overdense structures using the friends-of-friends (FoF) algorithm. We estimated the electron temperature of 2.0(-0.4)(+0.3) x 10(4) K from the H gamma and [O III]4363 lines in the stacked spectrum, indicating a metal-poor sample with a median gas phase metallicity of 12 + log(O/H) = 7.65(-0.15)(+0.26). With the most up-to-date strong line calibration based on NIRSpec observations, we find that the MZR shows a metal enhancement of similar to 0.2 dex at the high mass end in overdense environments. However, compared to the local fundamental metallicity relation (FMR), our galaxy sample at z > 5 shows a metal deficiency of similar to 0.2 dex relative to FMR predictions. We explain the observed trend of FMR with a simple analytical model, and we favor dilution from intense gas accretion over outflow to explain the metallicity properties at z > 5. The high-redshift galaxies are likely in a rapid gas accretion phase when their metal and gas contents are in a non-equilibrium state. According to model predictions, the protocluster members are closer to the gas equilibrium state than field galaxies and thus have a higher metallicity and are closer to the local FMR. Our results suggest that the accelerated star formation during protocluster assembly likely plays a key role in shaping the observed MZR and FMR, indicating a potentially earlier onset of metal enrichment in overdense environments at z approximate to 5-7.

We present the Cosmic Evolution Early Release Science (CEERS) Survey, a 77.2 hr Director’s Discretionary Early Release Science Program. CEERS demonstrates, tests, and validates efficient extragalactic surveys using coordinated, overlapping parallel observations with the JWST instrument suite, including NIRCam and MIRI imaging, NIRSpec low- ( R ∼ 100) and medium- ( R ∼ 1000) resolution spectroscopy, and NIRCam slitless grism ( R ∼ 1500) spectroscopy. CEERS targets the Hubble Space Telescope–observed region of the Extended Groth Strip field, supported by a rich set of multiwavelength data. CEERS facilitated immediate community science in both of the extragalactic core JWST science drivers “First Light” and “Galaxy Assembly,” including: (1) the discovery and characterization of large samples of galaxies at z ≳ 10 from ∼90 arcmin ^2 of NIRCam imaging, constraining their abundance and physical nature; (2) deep spectra of >1000 galaxies, including dozens of galaxies at 6 < z < 10, enabling redshift measurements and constraints on the physical conditions of star formation and black hole growth via line diagnostics; (3) quantifying the first bulge, bar, and disk structures at z > 3; and (4) characterizing galaxy mid-IR emission with MIRI to study dust-obscured star formation and supermassive black hole growth at z ∼ 1–3. As a legacy product for the community, the CEERS team has provided several data releases, accompanied by detailed notes on the data reduction procedures and notebooks to aid in reproducibility. In addition to an overview of the survey and the quality of the data, we provide science highlights from the first two years with CEERS data.