ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)
During the second half of Cycle 1 of the James Webb Space Telescope (JWST), we conducted the Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE) program. PASSAGE received the largest allocation of JWST observing time in Cycle 1, 591 hours of NIRISS observations to obtain direct near-IR imaging and slitless spectroscopy. About two thirds of these were ultimately executed, to observe 63 high-latitude fields in Pure Parallel mode. These have provided more than ten thousand near-infrared grism spectrograms of faint galaxies. PASSAGE brings unique advantages in studying galaxy evolution: A) Unbiased spectroscopic search, without prior photometric pre-selection. By including the most numerous galaxies, with low masses and strong emission lines, slitless spectroscopy is the indispensable complement to any pre-targeted spectroscopy; B) The combination of several dozen independent fields to overcome cosmic variance; C) Near-infrared spectral coverage, often spanning the full range from 1.0--2.3 μ\mum, with minimal wavelength gaps, to measure multiple diagnostic rest-frame optical lines, minimizing sensitivity to dust reddening; D) JWST's unprecedented spatial resolution, in some cases using two orthogonal grism orientations, to overcome contamination due to blending of overlapping spectra; E) Discovery of rare bright objects especially for detailed JWST followup. PASSAGE data are public immediately, and our team plans to deliver fully-processed high-level data products. In this PASSAGE overview, we describe the survey and data quality, and present examples of these accomplishments in several areas of current interest in the evolution of emission-line galaxy properties, particularly at low masses.
We create the first large-scale mock spectroscopic survey of gas absorption sightlines traversing the interstellar medium (ISM), circumgalactic medium (CGM), and intergalactic medium (IGM) surrounding galaxies of virtual Universes. That is, we create mock, or synthetic, absorption spectra by drawing lines-of-sight through cosmological hydrodynamical simulations, using a new mesh-free Voronoi ray-tracing algorithm. The result is the Synthetic Absorption Line Spectral Almanac (SALSA), which is publicly released on a feature-rich online science platform (this http URL). It spans a range of ions, transitions, instruments, observational characteristics, assumptions, redshifts, and simulations. These include, but are not limited to: (ions) HI, OI, CI, MgI, MgII, FeII, SiII, CaII, ZnII, SiIII, SiIV, NV, CII, CIV, OVI; (instruments) SDSS-BOSS, KECK-HIRES, UVES, COS, DESI, 4MOST, WEAVE, XSHOOTER; (model choices) with/without dust depletion, noise, quasar continua, foregrounds; (redshift) from z=0 to z~6; (ancillary data) integrated equivalent widths, column densities, distances and properties of nearby galaxies; (simulations) IllustrisTNG including TNG50, TNG-Cluster, EAGLE, and SIMBA. This scope is not fixed, and will grow and evolve with community interest and requests over time -- suggestions are welcome. The resulting dataset is generic and broadly applicable, enabling diverse science goals such as: (i) studies of the underlying physical gas structures giving rise to particular absorption signatures, (ii) galaxy-absorber and halo-absorber correlations, (iii) virtual surveys and survey strategy optimization, (iv) stacking experiments and the identification of faint absorption features, (v) assessment of data reduction methods and completeness calculations, (vi) inference of physical properties from observables, and (vii) apples-to-apples comparisons between simulations and data.
We present a multiphase, resolved study of the galactic wind extending from the nearby starburst galaxy NGC 4666. For this we use VLT/MUSE observations from the GECKOS program and HI data from the WALLABY survey. We identify both ionised and HI gas in a biconical structure extending to at least zz\sim8 kpc from the galaxy disk, with increasing velocity offsets above the midplane in both phases, consistent with a multiphase wind. The measured electron density, using [SII], differs significantly from standard expectations of galactic winds. We find electron density declines from the galaxy centre to 2\sim2 kpc, then rises again, remaining high (100300\sim100-300 cm3^{-3}) out to \sim5 kpc. We find that HI dominates the mass loading. The total HI mass outflow rate (above z >2z~>2 kpc) is between 513 M yr15-13~M_{\odot}~\rm yr^{-1}, accounting for uncertainties from disk-blurring and group interactions. The total ionised mass outflow rate (traced by Hα\alpha) is between 0.5 M yr10.5~M_{\odot}~\rm yr^{-1} and 5 M yr15~M_{\odot}~\rm yr^{-1}, depending on ne(z)n_e(z) assumptions. From ALMA/ACA observations, we place an upper-limit on CO flux in the outflow which correlates to 2.9 M yr1\lesssim2.9~M_{\odot}~\rm yr^{-1}. We also show that the entire outflow is not limited to the bicone, but a secondary starburst at the edge generates a more widespread outflow, which should be included in simulations. The cool gas in NGC 4666 wind has insufficient velocity to escape the halo of a galaxy of its mass, especially because most of the mass is present in the slower atomic phase. This strong biconical wind contributes to gas cycling around the galaxy.
JWST observations reveal numerous quiescent galaxies (QGs) at high redshift (z48z \sim 4-8), challenging models of early galaxy formation and quenching. Accurate number density estimates are crucial for comparison with theory but remain uncertain. We systematically study QGs at 0.5 < z < 8 using a mass-complete sample from the JWST/PRIMER survey with deep NIRCam and MIRI imaging. The MIRI data, probing rest-frame near-infrared at z38z \sim 3-8, are vital for robust stellar mass measurement and QG identification. We find that nearly all photometrically selected, point-like QG candidates located in the UVJ QG region are actually "Little Red Dots", for which the UVJ colors were wrongly estimated due to inaccurate photometric redshift estimation. MIRI reduces significantly contamination to high-mass QGs from star-forming galaxies, yielding lower number densities than previous studies. The evolution of QG number density is strongly mass-dependent. The density of high-mass QGs (\log (M_{\star}/M_{\odot}) > 10.3) decreases rapidly from n=1×105 Mpc3n = 1\times10^{-5}~\mathrm{Mpc^{-3}} at z=34z=3-4 to n=2×106 Mpc3n=2\times10^{-6}~\mathrm{Mpc^{-3}} at z=45z = 4-5, becoming negligible (n106 Mpc3n \lesssim 10^{-6}~\mathrm{Mpc^{-3}} ) at z > 5. Conversely, low-mass QGs (9<\log (M_{\star}/M_{\odot})<10.3) maintain a nearly constant number density (n3×106 Mpc3n\sim3\times10^{-6}~\mathrm{Mpc^{-3}}) across z=48z = 4-8. This suggests low-mass QGs at z > 4 are likely temporarily quenched, akin to mini-quenched galaxies. Comparison with major hydrodynamical and semi-analytical models shows most underestimate high-mass QG densities at z>4 and fail to reproduce the constant low-mass QG density at z>5.
We present a new method to calculate the polarised synchrotron emission of radio AGN sources using magnetic field information from 3-dimensional relativistic magnetohydrodynamical (RMHD) simulations. Like its predecessor, which uses pressure as a proxy for the magnetic field, this method tracks the spatially resolved adiabatic and radiative loss processes using the method adapted from the Radio AGN in Semi-analytic Environments formalism. Lagrangian tracer particles in RMHD simulations carried out using the PLUTO code are used to track the fluid quantities of each `ensemble of electrons' through time to calculate the radio emissivity ex-situ. By using the magnetic field directly from simulations, the full set of linear Stokes parameters I, Q, and U can be calculated to study the synthetic radio polarisation of radio AGN sources. We apply this method to a suite of RMHD simulations to study their polarisation properties. The turbulent magnetic field present in radio lobes influences the emission, causing a complex clumpy structure that is visible at high resolution. Our synthetic polarisation properties are consistent with observations; we find that the fractional polarisation is highest (approximately 50 percent) at the lobe edges. We show that for the same source, the integrated and mean fractional polarisation depends on viewing angle to the source. At oblique viewing angles the behaviour of the integrated and mean fractional polarisation over time depends on the morphology of the jet cocoon. Using Faraday rotation measures, we reproduce known depolarisation effects such as the Laing-Garrington depolarisation asymmetry in jets angled to the line of sight. We show that the hotspots and hence the Fanaroff-Riley classification become less clear with our new, more accurate method.
Detecting the cosmic 21-cm signal during the Epoch of Reionisation and Cosmic Dawn will reveal insights into the properties of the first galaxies and advance cosmological parameter estimation. Until recently, the primary focus for astrophysical parameter inference from the 21-cm signal centred on the power spectrum (PS). However, the cosmic 21-cm signal is highly non-Gaussian rendering the PS sub-optimal for characterising the cosmic signal. In this work, we introduce a new technique to analyse the non-Gaussian information in images of the 21-cm signal called the Wavelet Scattering Transform (WST). This approach closely mirrors that of convolutional neural networks with the added advantage of not requiring tuning or training of a neural network. Instead, it compresses the 2D spatial information into a set of coefficients making it easier to interpret while also providing a robust statistical description of the non-Gaussian information contained in the cosmic 21-cm signal. First, we explore the application of the WST to mock 21-cm images to gain valuable physical insights by comparing to the known behaviour from the 21-cm PS. Then we quantitatively explore the WST applied to the 21-cm signal by extracting astrophysical parameter constraints using Fisher Matrices from a realistic 1000 hr mock observation with the Square Kilometre Array. We find that: (i) the WST applied only to 2D images can outperform the 3D spherically averaged 21-cm PS, (ii) the excision of foreground contaminated modes can degrade the constraining power by a factor of ~1.5-2 with the WST and (iii) higher cadences between the 21-cm images can further improve the constraining power.
The Hector Galaxy Survey is a new optical integral field spectroscopy (IFS) survey currently using the AAT to observe up to 15,000 galaxies at low redshift (z < 0.1). The Hector instrument employs 21 optical fibre bundles feeding into two double-beam spectrographs to enable wide-field multi-object IFS observations of galaxies. To efficiently process the survey data, we adopt the data reduction pipeline developed for the SAMI Galaxy Survey, with significant updates to accommodate Hector's dual-spectrograph system. These enhancements address key differences in spectral resolution and other instrumental characteristics relative to SAMI, and are specifically optimised for Hector's unique configuration. We introduce a two-dimensional arc fitting approach that reduces the RMS velocity scatter by a factor of 1.2--3.4 compared to fitting arc lines independently for each fibre. The pipeline also incorporates detailed modelling of chromatic optical distortion in the wide-field corrector, to account for wavelength-dependent spatial shifts across the focal plane. We assess data quality through a series of validation tests, including wavelength solution accuracy, spectral resolution, throughput characterisation, astrometric precision, sky subtraction residuals, and flux calibration stability (4\% systematic offset when compared to Legacy Survey fluxes). We demonstrate that Hector delivers high-fidelity, science-ready datasets, supporting robust measurements of galaxy kinematics, stellar populations, and emission-line properties, and provide examples. Additionally, we address systematic uncertainties identified during the data processing and propose future improvements to enhance the precision and reliability of upcoming data releases. This work establishes a robust data reduction framework for Hector, delivering high-quality data products that support a broad range of extragalactic studies.
Neutral gas in galaxies during the Epoch of Reionisation regulates star formation, dust growth, and the escape of ionising photons, making it a key ingredient in understanding both galaxy assembly and reionisation. Yet, direct constraints on the HI content of galaxies at z>6 have been scarce. With JWST, Lyα\alpha damping wings in galaxy spectra can now provide a direct probe of this neutral component. We analyse JWST/NIRSpec prism spectra of 12 UV-luminous galaxies from the REBELS-IFU program at z~6.5-7.7, deriving HI column densities by modelling Lyα\alpha damping wings. Significant damped Lyα\alpha absorption is detected in eight galaxies, with NHI1021N_{\mathrm{HI}}\gtrsim10^{21} cm2^{-2}. We use the column densities and sizes derived for these sources to estimate their HI mass and compare with L[CII]L_{\mathrm{[CII]}}-MHIM_{\mathrm{HI}} calibrations. The resulting HI masses show a tentative correlation with those inferred from [CII], although the [CII]-based estimates are systematically larger, suggesting that the HI reservoirs may extend beyond the [CII]-emitting gas. We also combine the DLA-based measurements with FIR-derived dust-to-gas ratios, dust attenuation, and gas-phase metallicities. No correlation is found between DLA-based and FIR-based dust-to-gas ratios, but combining the REBELS-IFU sample with literature samples at lower metallicities reveals a strong correlation between AV/NHIA_{\mathrm{V}}/N_{\mathrm{HI}} and metallicity. These findings suggest that by z7z\sim7 massive galaxies can already host substantial, enriched reservoirs of neutral gas and dust, consistent with AVA_{\mathrm{V}}/NHIN_{\mathrm{HI}}-metallicity trends at lower redshift. At the highest redshifts (z>8z>8), however, we see tentative evidence for systematically lower AVA_{\mathrm{V}}/NHIN_{\mathrm{HI}} at fixed metallicity, which may point to pristine gas accretion or more efficient dust destruction/expulsion.
Using deep JWST/NIRSpec spectra from the Blue Jay survey, we perform the first systematic investigation of neutral gas content in massive galaxies at Cosmic Noon based on the Ca II H, K absorption lines. We analyze a sample of 9 galaxies at 1.8 < z < 2.8 with stellar masses > 10.6, for which we detect neutral gas absorption both in Ca II and in Na I. After removing the stellar continuum using the best-fit model obtained with Prospector, we fit the excess absorption due to neutral gas in the Ca II H, K doublet and in the Na I D doublet, together with nearby emission lines produced by ionized gas. We measure covering fractions between 0.2 and 0.9 from the Ca II H and K lines, which are spectrally well resolved in the NIRSpec R ~ 1000 observations, unlike the absorption lines in the Na I D doublet. We measure the velocity shift, velocity dispersion, and column density separately for Ca II and Na I. About half of the galaxies present blueshifted Ca II, indicative of an outflow of neutral gas, consistent with previous results based on Na I. The velocity shift and the column density measured from Ca II are correlated with those measured from Na I, implying that these absorption lines trace gas in similar physical conditions. However, the column densities are not in a 1:1 relation, meaning that the relative amount of Ca II and Na I atoms along the line of sight varies with the gas column density. After discussing possible reasons for this behavior, we derive an empirical relation between the column density of Ca II and the column density of Na I and, in a more indirect way, of neutral hydrogen H I. This calibration offers a new way to estimate the outflow mass and the mass outflow rate for the neutral phase from current and future JWST observations of massive galaxies at Cosmic Noon and beyond
A forward-modelling method unifies Tully-Fisher relation fitting with peculiar velocity field inference, applied to the Cosmicflows-4 dataset to derive a growth rate of structure (fσ8) of 0.35 ± 0.02 at z = 0.017. This approach also forecasts a 2-3 fold precision improvement for fσ8 from the upcoming WALLABY survey and refines the Tully-Fisher relation's characterization.
We report measurements of the galaxy two-point correlation function at cosmic dawn, using photometrically-selected sources from the JWST Advanced Deep Extragalactic Survey (JADES). The JWST/NIRCam dataset comprises approximately Ng7000N_g \simeq 7000 photometrically-selected Lyman Break Galaxies (LBGs), spanning in the redshift range 5\leq z&lt;11. The primary objective of this study is to extend clustering measurements beyond redshift z&gt;10, finding a galaxy bias b=9.6±1.7b=9.6\pm1.7 for the sample at z=10.6\overline{z} = 10.6. The result suggests that the observed sources are hosted by dark matter halos of approximately Mh1010.6 MM_{h}\sim 10^{10.6}~\mathrm{M_{\odot}}, in broad agreement with theoretical and numerical modelling of early galaxy formation during the epoch of reionization. Furthermore, the JWST JADES dataset enables an unprecedented investigation of clustering of dwarf galaxies two orders of magnitude fainter than the characteristic LL_* luminosity (i.e. with MF200W15.8M_{F200W}\simeq-15.8) during the late stages of the epoch of reionization at z6z\sim 6. By analyzing clustering as a function of luminosity, we find that b(MF200W)b(M_{F200W}) aligns with previous results for brighter galaxies and then decreases with MF200WM_{F200W}, as theoretically expected for fainter candidates. These initial results demonstrate the potential for further quantitative characterisation of the interplay between assembly of dark matter and light during cosmic dawn that the growing samples of JWST observations are enabling.
We combine JWST/NIRCam imaging and MUSE data to characterize the properties of galaxies in different environmental conditions in the cluster Abell2744 (z=0.3064z=0.3064) and in its immediate surroundings. We investigate how galaxy colors, morphology and star forming fractions depend on wavelength and on different parameterizations of environment. Our most striking result is the discovery of a ``red-excess'' population in F200W-F444W colors both in the cluster regions and the field. These galaxies have normal F115W-F150W colors, but are up to 0.8 mag redder than red sequence galaxies in F200W-F444W. They also have rather blue rest frame B-V colors. {Galaxies in the field and at the cluster virial radius are overall characterized by redder colors, but galaxies with the largest color deviations are found in the field and in the cluster core. Several results} suggest that mechanisms taking place in these regions might be more effective in producing these colors. Looking at their morphology, many cluster galaxies show signatures consistent with ram pressure stripping, while field galaxies have features resembling interactions and mergers. Our hypothesis is that these galaxies are characterized by dust enshrouded star formation: a JWST/NIRSpec spectrum for one of the galaxies is dominated by a strong PAH at 3.3μm\mu m, suggestive of dust obscured star formation. Larger spectroscopic samples are needed to understand if the color excess is due exclusively to dust-obscured star formation, and the role of environment in triggering it.
Stellar feedback drives multiphase gas outflows from starburst galaxies, but the interpretation of dust emission in these winds remains uncertain. To investigate this, we analyze new JWST mid-infrared images tracing polycyclic aromatic hydrocarbon (PAH) emission at 7.7 and 11.3~μ\mum from the outflow of the prototypical starburst M82 out to 3.23.2 kpc. We find that PAH emission shows significant correlations with CO, Hα\alpha, and X-ray emission within the outflow, though the strengths and behaviors of these correlations vary with gas phase and distance from the starburst. PAH emission correlates strongly with cold molecular gas, with PAH--CO scaling relations in the wind nearly identical to those in galaxy disks despite the very different conditions. The Hα\alpha--PAH correlation indicates that Hα\alpha traces the surfaces of PAH-bearing clouds, consistent with arising from ionized layers produced by shocks. Meanwhile the PAH--X-ray correlation disappears once distance effects are controlled for past 2~kpc, suggesting that PAHs are decoupled from the hot gas and the global correlation merely reflects the large-scale structure of the outflow. The PAH-to-neutral gas ratio remains nearly flat to 2~kpc, with variations following changes in the radiation field. This implies that the product of PAH abundance and dust-to-gas ratio does not change significantly over the inner portion of the outflow. Together, these results demonstrate that PAHs robustly trace the cold phase of M82's wind, surviving well beyond the starburst and providing a powerful, high-resolution proxy for mapping the life cycle of entrained cold material in galactic outflows.
JWST has enabled a new era of understanding high-z galaxy and black hole evolution with more than 30 high-z quasar host galaxy detections. Many of these observations imply galaxies with black holes that are overmassive compared to their low-z counterparts. However, the bright quasar point source removal may cause significant biases in these stellar mass measurements. We develop a simulation-based inference method to disentangle the quasar host galaxy stellar mass measurements from observational biases during the point source removal. We use the BlueTides simulation to generate mock images and perform point source removal on thousands of simulated high-z quasar host galaxies, constructing corrected host magnitude posteriors. We find that JWST photometry tends to either correctly recover or modestly misestimate host magnitudes, with a maximum magnitude underestimate of 0.21 mag. With our corrected magnitude posteriors, we perform SED fitting on each quasar host galaxy and compare the stellar mass measurement before and after the correction. We find that stellar mass estimates are generally robust, or overestimated by 0.3\leq0.3 dex. We also find that the stellar masses of a subset of hosts (J1120+0641, J0844-0132, J0911+0152, and J1146-0005) remain unconstrained, as key photometric bands provide only flux upper limits. Understanding these biases is essential to uncovering the evolutionary pathways of high-z quasars with their hosts.
The hosts of two low-luminosity high-z quasars, J2255+0251 and J2236+0032, were recently detected using JWST's NIRCam instrument. These represent the first high-z quasar host galaxy stellar detections and open a new window into studying high-z quasars. We examine the implications of the measured properties of J2255+0251 and J2236+0032 within the context of the hydrodynamic simulation BlueTides at z = 6.5. We find that these observed quasars fall on the BlueTides stellar to black hole mass relation and have similar luminosities to the brightest simulated quasars. We predict their star formation rates, estimating approximately 102310^{2-3} M/yrM_{\odot}/ \rm yr for both quasar hosts. J2255+0251 and J2236+0032's host galaxy radii also fall within estimates of the radii of the simulated host galaxies of similar luminosity quasars. We generate mock JWST NIRCam images of analogs to the observed quasars within BlueTides and perform a point source removal to illustrate both a qualitative and quantitative comparison of the measured and simulated radii and magnitudes. The quasar subtraction works well for similar luminosity quasars, and the recovered host images are consistent with what was observed for J2255+0251 and J2236+0032, further supporting the success of those observations. We also use our mock imaging pipeline to make predictions for the detection of J2255+0251 and J2236+0032's hosts in upcoming JWST observations. We anticipate that the simulation analogs of future high-z quasar host discoveries will allow us to make accurate predictions of their properties beyond the capabilities of JWST.
Recently, the Hydrogen Epoch of Reionization Array (HERA) collaboration has produced the experiment's first upper limits on the power spectrum of 21-cm fluctuations at z~8 and 10. Here, we use several independent theoretical models to infer constraints on the intergalactic medium (IGM) and galaxies during the epoch of reionization (EoR) from these limits. We find that the IGM must have been heated above the adiabatic cooling threshold by z~8, independent of uncertainties about the IGM ionization state and the nature of the radio background. Combining HERA limits with galaxy and EoR observations constrains the spin temperature of the z~8 neutral IGM to 27 K < T_S < 630 K (2.3 K < T_S < 640 K) at 68% (95%) confidence. They therefore also place a lower bound on X-ray heating, a previously unconstrained aspects of early galaxies. For example, if the CMB dominates the z~8 radio background, the new HERA limits imply that the first galaxies produced X-rays more efficiently than local ones (with soft band X-ray luminosities per star formation rate constrained to L_X/SFR = { 10^40.2, 10^41.9 } erg/s/(M_sun/yr) at 68% confidence), consistent with expectations of X-ray binaries in low-metallicity environments. The z~10 limits require even earlier heating if dark-matter interactions (e.g., through millicharges) cool down the hydrogen gas. Using a model in which an extra radio background is produced by galaxies, we rule out (at 95% confidence) the combination of high radio and low X-ray luminosities of L_{r,\nu}/SFR > 3.9 x 10^24 W/Hz/(M_sun/yr) and L_X/SFR<10^40 erg/s/(M_sun/yr). The new HERA upper limits neither support nor disfavor a cosmological interpretation of the recent EDGES detection. The analysis framework described here provides a foundation for the interpretation of future HERA results.
We present Keck/LRIS spectroscopy of seven isolated galaxy-quasar pairs at 0.4z0.60.4 \leq z \leq 0.6, each exhibiting ultra-strong MgII absorption (Wr,27963W_{r,2796} \geq 3 Å), probing both down-the-barrel and transverse gas flows. Down-the-barrel galaxy spectra reveal outflows in three galaxies (v=19v = 19 to 311311 km s1^{-1}) and inflows in five (v=61v = 61 to 361361 km s1^{-1}), including one system showing inflows and outflows simultaneously. All galaxies with detected inflows are below the star-forming main sequence, suggesting that they might be actively replenishing their gas reservoirs. Outflows have a mean covering fraction of Cf,out=0.5C_{f, \rm out}=0.5, whereas inflows show a lower average of Cf,in=0.3C_{f, \rm in}=0.3. Mass flow rates span M˙in=0.011.18\dot{M}_{\rm in} = 0.01-1.18 Myr1M_{\odot} \mathrm{yr}^{-1} for inflows and M˙out=0.231.03\dot{M}_{\rm out} = 0.23-1.03 Myr1M_{\odot}\mathrm{yr}^{-1} for outflows, yielding mass loading factors below unity and implying these galaxies cannot sustain their current level of star-formation rates. These results are based on the T 104\sim 10^4 K photoionised gas phase traced by MgII; additional accreting/outflowing material in other gas phases may also be present, but remains undetected in this study. Quasar sightlines consistently show redshifted inflow components and blueshifted outflow components, demonstrating that ultra-strong MgII absorbers trace baryon cycling out to impact parameters of D=15D = 15-31 kpc. Moreover, the unexpectedly high prevalence of inflows suggests that ultra-strong MgII absorbers offer a powerful strategy for future surveys to systematically map inflow and outflow cycles across cosmic time.
El Gordo (ACT-CL J0102-4915) is a massive galaxy cluster with two major mass components at redshift z=0.87z=0.87. Using SED fitting results from JWST/NIRCam photometry, the fraction of quenched galaxies in this cluster was measured in two bins of stellar mass: 9&lt;\log{({M_*}/\mathrm{M}_{\odot})}&lt;10 and 10\leq\log{({M_*}/\mathrm{M}_{\odot})}&lt;12. While there is no correlation between the quenched fraction and angular separation from the cluster's overall center of mass, there is a correlation between the quenched fraction and angular separation from the center of the nearest of the two mass components for the less-massive galaxies. This suggests that environmental quenching processes are in place at z1z\sim1, and that dwarf galaxies are more affected by those processes than massive galaxies.
Generally, merger likelihood increases in denser environments; however, the large relative velocities at the centres of dense clusters are expected to reduce the likelihood of mergers for satellite galaxies. Tidal features probe the recent merger histories of galaxies. The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will produce an unprecedented sample of tidal features around millions of galaxies. We use LSST-like mock observations of galaxies at z0z\sim0 from the EAGLE, IllustrisTNG and Magneticum Pathfinder cosmological-hydrodynamical simulations to predict the occurrence rates of tidal features around satellite galaxies across group and cluster environments in the velocity-radius projected phase-space diagram to investigate the impact of these environments on tidal feature occurrence. We find that ancient infallers in the projected phase-space exhibit a decreasing tidal feature fraction with increasing halo mass, whereas recent infallers in the projected phase-space show unchanging tidal feature fractions with halo mass. Our results show, for the first time in cosmological simulations, a suppression of tidal feature fractions in the central regions of galaxy clusters, indicating a reduced merger rate due to higher cluster-centric velocities and lower galaxy total masses in the cluster centres. Using a toy model, we show that the presence of more tidal features in the recent infaller zone and cluster outskirts suggests that tidal features occur in interactions within infalling groups and dissipate by the time they are ancient infallers, indicating a 3±2\lesssim3\pm2 Gyr survival time of tidal features within clusters.
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