Understanding the formation and evolution of the cosmic web of galaxies is a fundamental goal of both theoretical and observational cosmology, which use various tracers of the cosmic large-scale structure at an ever wider range of redshifts. Our principal aim is to advance the mapping of the cosmic web at high redshifts using observational and synthetic catalogues of quasars , which offer a powerful probe of structure formation and the validity of the concordance cosmological model at the largest scales in the Universe. In this analysis, we selected 708,483 quasars at 0.8<z<2.2 from the dataset; this enabled an extended reconstruction of the matter density field using 24,372 deg^2 sky area with a well-understood selection function, thus going beyond the capacity of previous studies. Using the method, we created catalogues of voids and clusters based on the estimation of the local density at quasar positions with Voronoi tessellation. We tested the consistency of data and 50 realistic mock catalogues, including various parameters of the voids and clusters in characteristic subsets of the data, and also measurements of the density profiles of these cosmic super-structures at R scales. Quaia REVOLVER Quaia h^ -1 ̊m Mpc We identified 12,820 voids and 41,154 clusters in the distribution of quasars. We found an sim5-10% level of agreement between data and the ensemble of the 50 mocks considering void and cluster radii, average inner density, and density profiles at all redshifts. In particular, we tested the role of survey mask proximity effects in void and cluster detection, which, although present in the data, are consistent in simulations and observations. Testing the extremes, the largest voids and clusters reach R_ Quaia ̊m eff h^ -1 ̊m Mpc and R_ ̊m eff h^ -1 ̊m Mpc , respectively, but without evidence for ultra-large cosmic structures exceeding the dimensions of the largest structures in our mock catalogues. Our data-analysis results highlight the capacity of quasars to robustly map the high-z cosmic web, further supported by the fully consistent statistical results from 50 mock catalogues. As an important deliverable, we share our density field estimation, void catalogues, and cluster catalogues with the public, which allows various additional cross-correlation probes in the high-z cosmic web. Quaia

Abstract We present a morphological analysis of Atacama Large Millimeter/submillimeter Array (ALMA) and James Webb Space Telescope (JWST) NIRCam images of nine dusty star-forming galaxies (DSFGs) at z spec ≈ 3.09, all embedded within the cosmic web filaments at the SSA22 protocluster core. The ALMA 870 μ m and 1.1 mm images are obtained at spatial resolutions ranging from 0.5″ to 0.05″ (350 pc at z = 3.09). The high-resolution images enable us to resolve inner structures traced by dust continuum, identifying compact dusty cores, clumps, and offset ridges within bars. Sérsic profile fitting was performed for both ALMA 870 μ m and NIRCam F444W images at comparable resolutions (∼0.15″). The Sérsic index measured for 870 μ m, masking bright regions, indicates values close to unity, suggesting that dust emission arises from disks with superimposed compact core components. For the JWST F444W images (restframe ∼1 μ m), the Sérsic indices range between n F444W ∼ 1–3, pointing to the coexistence of bulges and stellar disks in these DSFGs. A comparison of dust mass surface density, n F444W , and F200W–F444W color (restframe ∼0.5–1 μ m) reveals diversity among the DSFGs, likely reflecting different evolutionary stages, including some DSFGs with red cores, indicating ongoing rapid bulge growth phases heavily obscured by dust. The predominantly disklike morphologies observed in most DSFGs in the protocluster core contrast sharply with early-type morphologies that dominate the highest density environment in the local Universe. This suggests that we are witnessing the early formation of the morphology-density relation, as massive galaxies undergo rapid growth as late-type galaxies fueled by cosmic web gas filaments.

Context. Galaxy clusters trace the densest regions of the cosmic web and are crucial laboratories for studying the thermodynamic and chemical evolution of the intracluster medium (ICM). The massive galaxy cluster SPT-CL J0217−5014 ( z ∼ 0.53; M 500 ∼ 3 × 10 14 M ⊙ ) is one of the Swift X-Ray Telescope serendipitous galaxy clusters with the highest reported Fe abundance (∼1.3 ± 0.4 Z ⊙ within ∼ 1 . ′ 7) and a potentially disturbed morphology. Aims. SPT-CL J0217−5014 presents an intriguing opportunity to investigate ICM chemical enrichment and cool-core survival. With this study, we aim to evaluate its chemical and thermodynamic properties with a dedicated Chandra observation. Methods. Using new Chandra observations, we derived surface brightness profiles and dynamical state parameters. We also performed spectral fitting using different backgrounds to constrain the Fe abundance. We performed joint analysis of the X-ray surface brightness, temperature, and integrated Sunyaev-Zel’dovich Compton parameter to constrain the density profile. The DESI optical galaxy cluster catalogue was examined to explore its large-scale environment. Results. The X-ray morphology reveals a disturbed ICM with a surface brightness edge at ∼ 0 . ′ 26 (∼100 kpc) to the west and a tail-like feature extending towards the east. The best-fit metal abundance within $ 1{{\overset{\prime}{.}}}5 $ (∼0.7 R 500 ) is 0.61 +0.26 −0.23 Z ⊙ . The derived central electron number density, entropy, and cooling time classify this system as a non-cool-core cluster, suggesting that merger activity has likely disrupted the possible pre-existing cool core. At larger radii (∼1′−2′), we detected excess X-ray emission to the south spatially aligned with a filamentary distribution of red galaxies, indicating ongoing accretion along an intracluster filament. Based on the DESI DR9 cross-matched optical clusters and photometric redshifts, we identified three nearby lower-mass clusters that likely trace the large-scale structures, suggesting that SPT-CL J0217−5014 is the primary node of a dynamically active environment where past mergers and anisotropic accretion along cosmic filaments have shaped the present-day ICM.

Galaxy redshift surveys are one of the main ways of knowing how the universe as evolved. These surveys show how the matter forms a large-scale cosmic web of filaments, galaxy clusters and empty ‘voids. Dark matter can be seen to influence this pattern, which can be seen to still have the imprint of an early universe. A key pattern, the baryon acoustic oscillation scale, acts as a lengthtime tracker for tracking how the universe’s expansion has changed over time. In studying how galaxy clustering evolves with distance, surveys show that structure growth has slowed as dark energy began to dominate becoming a greater proportion of the total mass-energy content in the universe, causing the accelerated expansion of the universe. More recently, multi-messenger astronomy featuring gravitational waves, gamma rays and neutrinos have allowed astronomers to observe more cosmic events leading to greater evidence. Galaxy surveys provide some of the strongest evidence for the current model of the universe’s evolution from the Big Bang to the present day.

Abstract The role of large-scale environment in shaping the structural and kinematic properties of stellar halos remains an open question. We investigate whether the cosmic web environments affect the spatial and velocity anisotropies of stellar halos in Milky Way-mass galaxies. Using high-resolution data from the TNG50 simulation, we analyze 29 stellar halos from each environments: sheets, fillaments and clusters and quantify their spatial and kinematic anisotropies as a function of halo-centric radius. We find that stellar halos across all environments generally exhibit increasing spatial anisotropy with radius, with fluctuations corresponding to bound substructures. The velocity anisotropy profiles show radially dominated orbits on average, but also display significant local variation, including tangentially dominated regions. However, no statistically significant differences are observed in the mean spatial or velocity anisotropy profiles across environments, for either the total stellar halo population or for the in situ and ex situ components individually. The large scatter within each environment suggests that the formation of stellar halos is primarily driven by stochastic, small-scale processes such as satellite merger histories, rather than the large-scale geometry of the cosmic web. Our results imply that, at fixed halo mass, the influence of cosmic web environment on the structure of stellar halo is weak or highly non-deterministic. Possible environmental effects may be more prominent at higher masses where accretion is more anisotropic. Exploring this regime will require simulations with both larger volume and higher resolution.

Recent efforts to identify secondary variations in the halo occupation distribution (HOD) have primarily focused on simulations that examine the role of large-scale cosmic environments, such as superclusters, filaments, and under-dense regions or voids. If present, these variations can yield valuable insights into galaxy formation mechanisms, halo assembly processes, and the influence of external factors on the evolution of cosmic structure. We aim to explore whether the secondary trends in the HOD driven by the large-scale structure of the Universe are present observationally. In particular, we examined whether the HOD depends on the distance to key features of the cosmic web by explicitly quantifying these spatial relationships. We further analyzed whether HODs vary across different cosmic environments, as defined by critical point classifications, and assessed the influence of intrinsic galaxy properties, such as the central galaxy color. We created volume-limited galaxy samples from SDSS DR18 and used a group catalog to determine halo masses and to identify central and satellite galaxy membership. Additionally, we employed a DisPerSE catalog to locate critical points such as maxima, minima, and filaments in the cosmic web. We assessed how the HOD varies based on proximity to these features and analyzed these variations across five distinct cosmic environments. Furthermore, we investigated trends related to the color of central galaxies and tested the reliability of our results by using alternative DisPerSE catalogs generated with different smoothing scales and persistence thresholds. Our analysis confirms that the large-scale cosmic environment only weakly influences the HOD. However, second-order environmental dependences might be revealed through a multivariate approach that combines both local and large-scale environment metrics with intrinsic galaxy properties. Future investigations that employ next-generation surveys with improved statistical power, coupled with sophisticated modeling techniques, may provide the necessary precision to detect and characterize these subtle environmental correlations.

We present the first statistical observational study detecting filaments in the immediate surroundings of galaxies, i.e. the local web of galaxies. Simulations predict that cold gas, the fuel for star formation, is channeled through filamentary structures into galaxies. Yet, direct observational evidence for this process has been limited by the challenge of mapping the cosmic web at small scales. Using miniJPAS spectro-photometric data combined with spectroscopic DESI redshifts when available, we constructed a high-density observational galaxy sample spanning 0.2 < z < 0.8. Local filaments are detected within a 3 Mpc physical radius of each galaxy with stellar mass >10^10 using all nearby galaxies as tracers, combined with a probabilistic adaptation of the DisPerSE algorithm designed to overcome limitations due to photometric redshift uncertainties. Our methodology was tested and validated using mock catalogues built with random forest models applied to a simulated lightcone. Besides recovering the expected increase in galaxy connectivity (defined as the number of filaments attached to a galaxy) with stellar mass, we show that our connectivity measurements agree with 3D reference estimates from the mock galaxies. Thanks to these filament reconstructions, we explore the relation between small-scale connectivity and galaxy star formation rate, finding a mild positive trend which needs to be confirmed by follow-up studies with larger sample sizes. We propose galaxy connectivity to local filaments as a powerful and physically motivated metric of environment, offering new insights into the role of cosmic structure in galaxy evolution.

The environmental density of galaxies within the cosmic web provides insight into their 3D locations in filaments, voids, groups, and clusters of the large-scale structure of the Universe. This parameter reflects the distribution of baryonic matter and the influence of dark matter halos on galaxy evolution. Understanding environmental density is crucial for identifying the external physical processes — such as feedback from supernovae and active galactic nuclei, tidal interactions, ram-pressure stripping, and large-scale matter flows — that shape galaxies beyond their internal properties. In this article, we focus on the isolated galaxies with bars as the ensemble of galaxies for which the Milky Way galaxy-analogs belong. To obtain local environmental density parameters and verify the isolation criterion (v  500 km/s), we developed a Python-based pipeline operating in two redshift regimes: low (z0 < 0.02) and high (z0  0.02). Local densities Σ were estimated using both k-nearest neighbor and Voronoi tessellation methods and classified as void (Σ < 0.05), filament (0.05  Σ < 0.5), group (0.5  Σ < 2.0), and cluster (Σ  2.0). Our sample of 311 isolated barred galaxies from the 2MIG catalog, supplemented by Milky Way-analog systems (z < 0.07), covers the northern sky. We find 157 galaxies in voids, 84 in filaments, 27 in groups, and 11 in clusters; 30 exhibit no detectable neighbors. A subset of 67 galaxies occupies extremely low-density regions (Σ₃D < 0.01 gal Mpc⁻³), while 22 have their nearest companion farther than 5 Mpc, suggesting their location within extended cosmological voids. The Milky Way (Σ₅NN  0.13 gal Mpc⁻³, R  2.1 Mpc) and its close analog NGC 3521 both reside in filamentary environments, consistent with intermediate-density surroundings at the boundary of a nearby void. For galaxies with z > 0.02, the estimated local densities of the Milky Way and the analyzed systems allow us to identify three additional candidates that satisfy the supplementary environmental density criterion. Based on 3D Voronoi tessellation density estimates, one Milky Way-analog candidate is CGCG 208-043, while according to the fifth-nearest-neighbor approach, the candidates are NGC 5231 and CGCG 047-026. These results highlight the importance of local environmental density as an additional indicator in the search for Milky Way galaxy-analogs.

Abstract We present the first detailed, spatially resolved study of the circumgalactic medium (CGM) surrounding the low-mass, low-redshift star-forming galaxy J0910b (SDSS J091458.61+110845.1; M ⋆ ∼ 10 9.2 M ⊙ , z = 0.096), focusing on its gas dynamics, ionization mechanisms, and kinematics. J0910b is the lowest-mass galaxy in our low-redshift CGM survey using the Keck Cosmic Web Imager (KCWI). Using KCWI integral field spectroscopy and CLOUDY modeling, we map the ionization structure and velocity field of the CGM through H α , [O III ] λ 5007, and [O II ] λλ 3727, 3729 emission. We detect a predominantly cool ( T ∼ 10 4 K) ionized halo extending to ∼35 kpc (∼0.35 R vir ), with a complex structure including a counterrotating component and two filamentary inflows. The counterrotating CGM contains ∼7.4 × 10 9 M ⊙ of ionized gas—nearly 5 times the stellar mass—and exhibits a positive radial metallicity gradient, rising from 0.2 Z ⊙ at 9 kpc to 0.65 Z ⊙ at 16 kpc. Velocity dispersion maps reveal a shell-like structure near the interstellar medium-CGM interface, suggesting feedback-driven outflows that redistributed enriched gas. In contrast, the filaments show low metallicities (∼0.07 Z ⊙ ), high specific angular momentum ( j ∼ 3.7 × 10 3 kpc km s −1 ), and an accretion rate of 0.05 M ⊙ yr −1 , consistent with an intergalactic origin. Together, these components reveal a dynamically rich CGM. The counterrotating gas dominates the halo’s mass, accounts for ∼33% of the cosmic baryon budget, and must be continuously replenished ( t cool ∼ 0.3–2 Myr). These results suggest a long-lived, regulated CGM that governs star formation through angular momentum exchange and gas recycling.

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 ∼20% of the rotational velocities may reflect motions along inflowing streams from the cosmic web rather than being generated by disk instability.

Abstract Using a large observational sample from the Sloan Digital Sky Survey, we investigate the spatial alignment between galaxy pairs and their local cosmic filaments. Focusing on pairs with stellar masses and separations comparable to the Milky Way–Andromeda (MW–M31) system, we measure the angle between the pair connecting line and the orientation of the host filament, determined using a filament catalog constructed via the Bisous model. Our analysis reveals a statistically significant tendency of galaxy pairs to align their connecting lines along their host filaments, manifesting as an overall ∼7% excess of alignment angles smaller than the MW–M31 case compared to a random distribution. Crucially, the strength of this alignment exhibits a strong dependence on the distance to the filament spine. Pairs located within 0.2 Mpc from the filament spine show the strongest alignment, while those beyond 1 Mpc display no significant alignment. Furthermore, we identify a bimodal distribution of alignment angles near filament cores, suggesting distinct dynamical populations potentially associated with infall and interaction processes. Our results provide robust observational support for theoretical models in which anisotropic accretion and tidal forces within the cosmic web drive galaxy pair evolution. They also position the MW–M31 system as a representative filament-aligned pair, offering insights into Local Group assembly. This study demonstrates the cosmic web’s critical role in dictating pair orientations and motivates future work with kinematic data to unravel galaxy–environment interplay.

Abstract We propose a UNet-based deep learning model to reconstruct the real-space dark matter (DM) velocity field from the redshift-space distribution of sparse DM halos. Using various statistical measures, we show that the reconstructed velocity components—including velocity magnitude, momentum, and divergence—closely match the ground truth, achieving better than 10% relative error and a correlation coefficient of 0.88. In the power spectrum comparison over k ∈ [0.05, 0.3] h Mpc −1 , the UNet reconstruction outperforms linear theory and agrees with the true field within 2 σ . The model also effectively corrects redshift-space distortions (RSD), yielding unbiased power spectrum multipoles of DM fields within 2 σ . Notably, UNet remains robust even with incomplete halo mass information. These results highlight the model’s broad applicability to cosmological analyses, including RSD, cosmic web studies, the kinetic Sunyaev–Zel’dovich effect, and baryon acoustic oscillation reconstruction.

Abstract Lyα intensity mapping is emerging as a new probe of faint galaxies consisting the cosmic web that elude traditional surveys. However, the resonant nature of Lyα radiative transfer complicates the interpretation of observed data. In this study, we develop a fast and accurate analytic prescription for computing the Lyα intensity field on Mpc scales in the post-reionization Universe. Motivated by insights from Monte Carlo radiative transfer (MCRT) experiments, we exploit the fact that in a highly ionized intergalactic medium (IGM) with negligible damping-wing opacity, cosmological redshifting quickly drives Lyα photons out of resonance, terminating the scattering process and simplifying their large-scale behavior. Photons emitted blueward of the Lyα line center tend to scatter on a thin, nearly spherical surface of last scattering, with a radius determined by the redshifting distance to resonance. Based on this behavior, we derive closed-form expressions for the scattered emissivity and projected surface brightness that depend only on the source spectrum, the HI density, and the peculiar velocity field. When applied to a source in a realistically simulated IGM at z = 3, our model shows mild discrepancies with MCRT results within a physical Mpc of the host halo, where strong gravitational infall redistributes the scattered photons, but achieves better than 5% accuracy beyond that distance in angle-averaged radial surface brightness profile. Our prescription offers a computationally efficient alternative to MCRT for forward-modeling Lyα intensity maps from cosmological simulations, enabling the inference of underlying cosmological and astrophysical parameters from future observations.

Fossil groups (FGs) are groups or clusters of galaxies with a single, massive, central galaxy dominating their luminosity distribution, and with a clear lack of L^* galaxies. The physical reason for the large magnitude gap (Δ m_ ) in these systems is still a matter for investigation. It could originate in an early formation of FGs, followed by passive evolution in which all L^* galaxies merged with the central one, and/or it could be related to the fact that galaxies accreting on the FGs move on very radial orbits, reach small pericentric radii, and are merged on shorter timescales than regular cluster galaxies. The latter properties could be linked with the peculiar position of FGs within the cosmic web. To shed light on the origin of FGs, we determine the velocity anisotropy profile β(r) of the fossil cluster A267, which is related to the orbital distribution of cluster galaxies. This is the first individual FG for which the orbital distribution of its galaxies is determined. We aim to confirm previous findings based on stack samples that indicate that FGs, on average, host galaxies on more radial orbits than normal clusters. We started with a sample of 2315 redshifts for galaxies in the field of A267 and we determined the membership for 329 of them. Of these, 174 are located within the virial radius of the cluster, and we used them as tracers of the gravitational potential of the cluster to solve the Jeans equation for dynamical equilibrium using the algorithm. As a result, we obtained the cluster mass profile M(r) and β(r). We also estimated M(r) from the X-ray data by applying the hydrostatic equilibrium. A comparison of the and X-ray-determined M(r)s allows us to estimate the cluster hydrostatic mass bias, which we find to be consistent with previous findings. The anisotropy parameter β(r) indicates tangential orbits for the galaxies near the cluster centre and increasingly radial orbits in the external regions. We checked that our results are not affected by the presence of subclusters and by the choice of the models for M(r) and β(r). The A267 β(r) is very similar to that previously determined for a stack of large Δ m_ systems. Our analysis therefore confirms that FGs are characterized by more radial orbits for their member galaxies than the average cluster population. We speculate that this different orbital distribution might be an important element in creating a large Δ m_

Abstract Galactic warps are common in disk galaxies. While often attributed to galaxy–galaxy tides, a nonspherical dark matter halo has also been proposed as a driver of disk warping. We investigate links among warp morphology, satellite distribution, and large-scale structure using the Sloan Digital Sky Survey catalog of warped disks compiled by W.-B. G. Zee et al. Warps are classified into 244 S- and 127 U-types, hosting 1373 and 740 satellites, respectively, and are compared to an unwarped control matched in stellar mass, redshift, and local density. As an indirect, population-level proxy for the host halo’s shape and orientation, we analyze the stacked spatial distribution of satellites. Warped hosts show a significant anisotropy: an excess at 45° < ϕ < 90° (measured from the host major axis), peaking at P ( ϕ ) ≃ 0.003, versus nearly isotropic controls. Satellites of S-type warps preferentially align with the nearest cosmic filament, whereas those of U-type warps are more often perpendicular. The incidence of warps increases toward filaments ( r fila < 4 Mpc h −1 ), while the number of satellites around warped hosts remains approximately constant with filament distance, indicating a direct influence of the large-scale environment. We discuss possible links between galactic warps and the cosmic web, including anisotropic tidal fields and differences in evolutionary stage.

Abstract Fast radio bursts (FRBs) are unique probes of extragalactic ionized baryonic structure as each signal, through its burst properties, holds information about the ionized matter it encounters along its sightline. FRB 20200723B is a burst with a scattering timescale of τ 400 MHz > 1 s at 400 MHz and a dispersion measure of DM ∼244 pc cm −3 . Observed across the entire Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB frequency band, it is the single-component burst with the largest scattering timescale yet observed by CHIME/FRB. The combination of its high scattering timescale and relatively low dispersion measure present an uncommon opportunity to use FRB 20200723B to explore the properties of the cosmic web it traversed. With an ∼arcminute-scale localization region, we find the most likely host galaxy is NGC 4602 (with PATH probability P ( O ∣ x ) = 0.985), which resides ∼30 Mpc away within a cosmic sheet structure on the outskirts of the Virgo Cluster. We place an upper limit on the average free electron density of this cosmic structure of 〈 n e 〉 < 4 . 6 − 2.0 + 9.6 × 1 0 − 5 cm −3 , broadly consistent with expectations from cosmological simulations. We investigate whether the source of scattering lies within the same galaxy as the FRB, or at a farther distance from an intervening structure along the line of sight. Comparing with Milky Way pulsar observations, we suggest the scattering may originate from within the host galaxy of FRB 20200723B.

The intrinsic properties of galaxies are influenced by their environments, underscoring the environment's critical role in galaxy formation and evolution. Traditionally, these environments are categorized into four fixed classifications: knots, filaments, walls, and voids, which collectively describe the complex organization of galaxies within large-scale structures. We propose an alternative description that complements the traditional quadripartite categorization by introducing a continuous framework, allowing for a more nuanced examination of the relationship between the intrinsic properties of galaxies and their environments. This complementary description is applied using one of the most prevalent methodologies: categorization using the eigenvalues of the Hessian matrix extracted from the matter density field. We integrated our findings into a semi-analytical model of galaxy formation, combined with cosmological numerical simulations, to analyze how the intrinsic properties of galaxies are influenced by environmental changes. In our study, we find a continuous distribution of eigenvalue ratios, revealing a clear dependence of galaxy properties on their surrounding environments. This method allowed us to identify critical values at which transitions in the behavior of key astrophysical galaxy properties become evident.

We report the discovery of a massive Lyα nebula (potentially largest ever discovered), RaJav, at z=2.25, associated with a quasar pair: the bright SDSS J162029.07+433451.1 (hereafter J1620+4334) and the faint newly discovered quasar JPAS-9600-10844, at 2.265 ± 0.021 using the early data release (17 deg^2) of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS). The quasar JPAS-9600-10844 embedded in the nebula is located at ∼ 60.2 kpc (7.3 from J1620+4334, and shows a compact structure with broad emission lines (> 3000 km/s), typical of active galactic nuclei (i.e., Lyα łambda1216 and CIV łambda1548). At a 2σ surface brightness (SB) contour of ∼ 1.86 erg s^-1 cm^-2 arcsec^-2, the nebula extends beyond 100 kpc and has a total Lyα luminosity of ∼ 5.8 ± 0.7 erg s^-1 which signifies the presence of an enormous Lyα nebula (ELAN). The nebula traces an overdensity of quasars at a redshift of 2.2-2.3 consistent with the progenitor of a massive galaxy cluster. The extended CIV emission with luminosity of ∼ 3.7 ± 0.5 erg s^-1 indicates that the circumgalactic medium (CGM) is metal-enriched and not primordial. The current J-PAS observations suggest photoionization and shocks due to outflows as possible ionization mechanisms. The faint extended far-UV and near-UV continuum emission likely points to ongoing star formation around the two quasars, suggesting a complex interaction in their environments. These findings provide new insights into the environment of quasars and their role in shaping the dynamics and evolution of the CGM at cosmic noon. Further spectroscopic observations will be required to fully characterize the object's nature and its kinematic properties. This study demonstrates the unique capability of J-PAS to detect massive and rare Lyα nebulae, providing new insights into their properties, environments, and connections to large-scale structures in the cosmic web such as filaments and overdensities in a large cosmological volume.

Abstract We combine deep photometric data in the COSMOS and XMM-LSS fields with high-resolution cosmological hydrodynamical simulations to explore two key questions: (1) how does the galaxy stellar mass function, particularly in the dwarf (M⋆ < 109.5 M⊙) regime, vary with environment, defined as distance from the large-scale structure (LSS) traced by nodes and filaments in the cosmic web? (2) is there a generic ‘missing dwarfs’ problem in ΛCDM predictions when all environments – and not just satellites around Milky Way like galaxies – are considered? The depth of the observational data used here enables us to construct complete, unbiased samples of galaxies, down to M⋆ ∼ 107 M⊙ and out to z ∼ 0.4. Strong environmental differences are found for the galaxy stellar mass function when considering distance from LSS. As we move closer to LSS, the dwarf mass function becomes progressively flatter and the knee of the mass function shifts to larger stellar masses, both of which result in a higher ratio of massive to dwarf galaxies. While the stellar mass functions from the three simulations (NewHorizon, TNG50 and FIREbox) considered here do not completely agree across the dwarf regime, there is no evidence of a generic missing dwarfs problem in the context of ΛCDM, akin to the results of recent work that demonstrates that there is no missing satellites problem around Galactic analogues.

Cosmic voids are vast underdense regions in the cosmic web that encode crucial information about structure formation, the composition of the Universe, and its expansion history. Due to their lower density, these regions are less affected by non-linear gravitational dynamics, making them suitable candidates for analysis using semi-analytic methods. We assess the accuracy of the code, a fast tool for generating dark matter halo catalogs based on Lagrangian perturbation theory, in modeling the statistical properties of cosmic voids. We validate this approach by comparing the resulting void statistics measured from to those obtained from N-body simulations. We generate a set of simulations using and assuming a fiducial cosmology and varying the resolution. For a given resolution, the simulations share the same initial conditions between the two codes. Snapshots are saved at multiple redshifts and post-processed using the watershed void finder ̌ide to identify cosmic voids. For each simulation, we measure the following statistics: void size function, void ellipticity function, core density function, and the void radial density profile. We use these statistics to quantify the accuracy of relative to in the context of cosmic voids. We find agreement for all void statistics at better than 2σ between and with no systematic difference in redshift trends. This demonstrates that the code can reliably produce void statistics with high computational efficiency compared to full N-body simulations.