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We combined data from the Sloan Digital Sky Survey (SDSS) and the Arecibo Legacy Fast ALFA Survey (ALFALFA) to establish the HI mass vs. stellar mass and halo mass scaling relations using an abundance matching method that is free of the Malmquist bias. To enable abundance matching, a cross-match between the SDSS DR7 galaxy group sample and the ALFALFA HI sources provides a catalog of 16520 HI-galaxy pairs within 14270 galaxy groups (halos). By applying the observational completeness reductions for both optical and HI observations, we used the remaining 8180 ALFALFA matched sources to construct the model constraints. Taking into account the dependence of HI mass on both the galaxy and group properties, we establish two sets of scaling relations: one with a combination of stellar mass, (g-r) color and halo mass, and the other with stellar mass, specific star-formation rate (sSFR), and halo mass. We demonstrate that our models can reproduce the HI mass component as both stellar mass and halo mass. Additional tests showed that the conditional HI mass distributions as a function of the cosmic web type and the satellite fractions were well recovered. [ABSTRACT FROM AUTHOR]

The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. The cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic nuclei (AGN) with long duty cycles. The outflows from the central engine tightly couple with the surrounding gaseous medium and provide the dominant heating source, preventing runaway cooling. Every major modern hydrodynamical simulation suite now includes a prescription for AGN feedback to reproduce the realistic populations of galaxies. However, the mechanisms governing the feeding/feedback cycle between the central black holes and their surrounding galaxies and halos are still poorly understood. Galaxy groups are uniquely suited to constrain the mechanisms governing the cooling–heating balance, as the energy supplied by the central AGN can exceed the gravitational binding energy of halo gas particles. Here, we provide a brief overview of our knowledge of the impact of AGN on the hot atmospheres of galaxy groups, with a specific focus on the thermodynamic profiles of the groups. We then present our on-going efforts to improve on the implementation of AGN feedback in galaxy evolution models by providing precise measurements of the properties of galaxy groups. We introduce the XMM-Newton Group AGN Project (X-GAP), a large program on XMM-Newton targeting a sample of 49 galaxy groups out to R 500 c . [ABSTRACT FROM AUTHOR]

The boundaries of galaxy groups and clusters are defined by the interplay between the Newtonian attractive force and the decoupling from the local expansion of the Universe. This work extends the definition of a zero radial acceleration surface (ZRAS) and the turnaround surface (TS) for a general distribution of the masses in an expanding background, governed by the cosmological constant. We apply these definitions to different galaxy groups in the local Universe, mapping these groups up to ten megaparsec distances. We discuss the dipole and the quadrupole rate for the Local Group of Galaxies and the implementations on the Hubble diagram correction and galaxy groups virialization. With these definitions, we present the surfaces showing the interplay between the local expansion vs the local Newtonian attraction for galaxy groups in the local Universe. Further, we estimate the masses of different galaxy groups and show that the inclusion of the Cosmological Constant in the analysis predicts these masses to be higher by 5-10%. For instance the Local Group of galaxies is estimated to be (2.47±0.08)⋅1012M⊙. For the groups with enough tracers close to the TS, the contribution of the Cosmological Constant makes the masses to be even higher. The results show the importance of including the local cosmic expansion in analyzing the Cosmic Flow of the local Universe.

This review examines the relationship between black hole activity and kinematic gas–star misalignment in brightest group galaxies (BGGs) with different merger rates. The formation history of galaxy groups is assessed through "age-dating" as an indicator of distinct major mergers involving the BGGs. BGGs within groups characterized by a higher frequency of major mergers are more likely to host active SMBHs. A consistent correlation is identified between the level of black hole activity, as indicated by the 1.4 GHz and 325 MHz radio emissions, and the degree of kinematic misalignment between the gas and stellar components in BGGs. In dynamically fossil groups, where black hole accretion rate is relatively (∼1 dex) lower due to the lack of recent (≤1 Gyr) major mergers, there is reduced (∼30%) misalignment between the gas and stellar components of BGGs compared to non-fossil groups. Additionally, this study reveals that BGGs in non-fossil groups show higher levels of star formation rate and increased occurrence of mergers, contributing to observed color differences. Exploring the properties and dynamics of the gas disk influenced by mechanical AGN feedback through hydrodynamic simulations suggests that AGN wind-induced effects further lead to the persistent gas misalignment in the disk around the supermassive black hole. [ABSTRACT FROM AUTHOR]

FRB 20220610A is a high-redshift fast radio burst (FRB) that has not been observed to repeat. Here, we present rest-frame UV and optical Hubble Space Telescope observations of the field of FRB 20220610A. The imaging reveals seven extended sources, one of which we identify as the most likely host galaxy with a spectroscopic redshift of z = 1.017. We spectroscopically confirm three additional sources to be at the same redshift and identify the system as a compact galaxy group with possible signs of interaction among group members. We determine the host of FRB 20220610A to be a star-forming galaxy with a stellar mass of ≈10 ^9.7 M _⊙ , mass-weighted age of ≈2.6 Gyr, and star formation rate (integrated over the last 100 Myr) of ≈1.7 M _⊙ yr ^−1 . These host properties are commensurate with the star-forming field galaxy population at z ∼ 1 and trace their properties analogously to the population of low- z FRB hosts. Based on estimates of the total stellar mass of the galaxy group, we calculate a fiducial contribution to the observed dispersion measure from the intragroup medium of ≈90–182 pc cm ^−3 (rest frame). This leaves a significant excess of ${515}_{-272}^{+122}$ pc cm ^−3 (in the observer frame); further observation will be required to determine the origin of this excess. Given the low occurrence rates of galaxies in compact groups, the discovery of an FRB in one demonstrates a rare, novel environment in which FRBs can occur. As such groups may represent ongoing or future mergers that can trigger star formation, this supports a young stellar progenitor relative to star formation.

We present the discovery of a new H i structure in the NGC 7194 group from the observations using the Karl G. Jansky Very Large Array. NGC 7194 group is a nearby ( z ∼ 0.027) small galaxy group with five quiescent members. The observations reveal a 200 kpc long H i plume that spans the entire group with a total mass of M _H I = 3.4 × 10 ^10 M _⊙ . The line-of-sight velocity of the H i gas gradually increases from south (7200 km s ^−1 ) to north (8200 km s ^−1 ), and the local velocity dispersion is up to 70 km s ^−1 . The structure is not spatially coincident with any member galaxies but it shows close associations with a number of blue star-forming knots. Intragroup H i gas is not rare, but this particular structure is still one of the unusual cases in the sense that it does not show any clear connection with sizable galaxies in the group. We discuss the potential origins of this large-scale H i gas in the NGC 7194 group and its relation with the intergalactic star-forming knots. We propose that this H i feature could have originated from tidal interactions among group members or the infall of a late-type galaxy into the group. Alternatively, it might be leftover gas from flyby intruders.

Quantifying the connection between galaxies and their host dark matter halos has been key for testing cosmological models on various scales. Below M ⋆ ∼ 109 M ⊙, such studies have primarily relied on the satellite galaxy population orbiting the Milky Way (MW). Here we present new constraints on the connection between satellite galaxies and their host dark matter subhalos using the largest sample of satellite galaxies in the Local Volume (D ≲ 12 Mpc) to date. We use 250 confirmed and 71 candidate dwarf satellites around 27 MW-like hosts from the Exploration of Local VolumE Satellites (ELVES) Survey and use the semianalytical SatGen model for predicting the population of dark matter subhalos expected in the same volume. Through a Bayesian model comparison of the observed and the forward-modeled satellite stellar mass functions (SSMFs), we infer the satellite stellar-to-halo mass relation. We find that the observed SSMF is best reproduced when subhalos at the low-mass end are populated by a relation of the form M ⋆ ∝ M peak α , with a moderate slope of α const = 2.10 ± 0.01 and a low scatter, constant as a function of the peak halo mass, of σ const = 0.06 − 0.05 + 0.07 . A model with a steeper slope (α grow = 2.39 ± 0.06) and a scatter that grows with decreasing M peak is also consistent with the observed SSMF but is not required. Our new model for the satellite–subhalo connection, based on hundreds of Local Volume satellite galaxies, is in line with what was previously derived using only MW satellites. [ABSTRACT FROM AUTHOR]

The co-evolution between supermassive black holes and their environment is most directly traced by the hot atmospheres of dark matter halos. The cooling of the hot atmosphere supplies the central regions with fresh gas, igniting active galactic nuclei (AGN) with long duty cycles. The outflows from the central engine tightly couple with the surrounding gaseous medium and provide the dominant heating source, preventing runaway cooling. Every major modern hydrodynamical simulation suite now includes a prescription for AGN feedback to reproduce the realistic populations of galaxies. However, the mechanisms governing the feeding/feedback cycle between the central black holes and their surrounding galaxies and halos are still poorly understood. Galaxy groups are uniquely suited to constrain the mechanisms governing the cooling–heating balance, as the energy supplied by the central AGN can exceed the gravitational binding energy of halo gas particles. Here, we provide a brief overview of our knowledge of the impact of AGN on the hot atmospheres of galaxy groups, with a specific focus on the thermodynamic profiles of the groups. We then present our on-going efforts to improve on the implementation of AGN feedback in galaxy evolution models by providing precise measurements of the properties of galaxy groups. We introduce the XMM-Newton Group AGN Project (X-GAP), a large program on XMM-Newton targeting a sample of 49 galaxy groups out to R500c.

This review examines the relationship between black hole activity and kinematic gas–star misalignment in brightest group galaxies (BGGs) with different merger rates. The formation history of galaxy groups is assessed through “age-dating” as an indicator of distinct major mergers involving the BGGs. BGGs within groups characterized by a higher frequency of major mergers are more likely to host active SMBHs. A consistent correlation is identified between the level of black hole activity, as indicated by the 1.4 GHz and 325 MHz radio emissions, and the degree of kinematic misalignment between the gas and stellar components in BGGs. In dynamically fossil groups, where black hole accretion rate is relatively (∼1 dex) lower due to the lack of recent (≤1 Gyr) major mergers, there is reduced (∼30%) misalignment between the gas and stellar components of BGGs compared to non-fossil groups. Additionally, this study reveals that BGGs in non-fossil groups show higher levels of star formation rate and increased occurrence of mergers, contributing to observed color differences. Exploring the properties and dynamics of the gas disk influenced by mechanical AGN feedback through hydrodynamic simulations suggests that AGN wind-induced effects further lead to the persistent gas misalignment in the disk around the supermassive black hole.

We combine James Webb Space Telescope (JWST) and Hubble Space Telescope imaging with Atacama Large Millimeter Array CO(2–1) spectroscopy to study the highly turbulent multiphase intergalactic medium (IGM) in Stephan's Quintet on 25–150 pc scales. Previous Spitzer observations revealed luminous H2 line cooling across a 45 kpc-long filament, created by a giant shock wave, following the collision with an intruder galaxy, NGC 7318b. We demonstrate that the Mid-Infrared Instrument/F1000W/F770W filters are dominated by 0–0 S(3) H2 and a combination of polycyclic aromatic hydrocarbon and 0–0 S(5) H2 emission. These observations reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions, and likely destruction/recycling within different phases of the IGM. In 1 kpc-scaled structure, warm H2 was seen to form a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H2. In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H2 suggesting a cloud–cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H2 lines throughout Stephan's Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. A full picture of the diverse kinematics and excitation of the warm H2 will require future JWST mid-IR spectroscopy. The current observations reveal the rich variety of ways that different gas phases can interact with one another. [ABSTRACT FROM AUTHOR]

At least half of the local galaxies reside in galaxy groups, which indicates that the group is the common environment where galaxies evolve. Therefore, it is important to probe how significantly galaxies are affected by group environmental processes, in order to obtain a better understanding of galaxy evolution. We carried out a new CO imaging survey for 31 galaxies in the IC 1459 and NGC 4636 groups, using the Atacama Compact Array, to study the effect of the group environment on the molecular gas properties and the star formation activity. With our resolved CO data, combined with high-resolution H i images, we find asymmetric CO and H i distributions in the group galaxies. Compared to isolated galaxies, group members have relatively low molecular gas fraction and low star formation rate. These results suggest that the group environment can change the properties of cold gas components and star formation in group galaxies. [ABSTRACT FROM AUTHOR]

We perform a semi-automated search for strong gravitational lensing systems in the 9000 deg2 Dark Energy Camera Legacy Survey (DECaLS), part of the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. The combination of the depth and breadth of these surveys are unparalleled at this time, making them particularly suitable for discovering new strong gravitational lensing systems. We adopt the deep residual neural network architecture developed by Lanusse et al. for the purpose of finding strong lenses in photometric surveys. We compile a training sample that consists of known lensing systems in the Legacy Surveys and the Dark Energy Survey as well as non-lenses in the footprint of DECaLS. In this paper we show the results of applying our trained neural network to the cutout images centered on galaxies typed as ellipticals in DECaLS. The images that receive the highest scores (probabilities) are visually inspected and ranked. Here we present 335 candidate strong lensing systems, identified for the first time.

The galaxy group NGC 6338 is one of the most violent group–group mergers known to date. While the central dominant galaxies rush at each other at 1400 km s−1 along the line of sight, with dramatic gas heating and shock fronts detected, the central gas in the BCGs remains cool. There are also indications of feedback from active galactic nuclei, and neither subcluster core has been disrupted. With our deep radio uGMRT data at 383 and 650 MHz, we clearly detect a set of large, old lobes in the southern BCG coinciding with the X-ray cavities, while the northern and smaller BCG appears slightly extended in the radio. The southern BCG also hosts a smaller younger set of lobes perpendicular to the larger lobes, but also coinciding with the inner X-ray cavities and matching the jet direction in the parsec-resolution VLBA image. Our spectral analysis confirms the history of two feedback cycles. The high radio frequency analysis classifies the compact source in the southern BCG with a power law, while ruling out a significant contribution from accretion. The radio lightcurve over three decades shows a change about 10 yr ago, which might be related to ongoing feedback in the core. The southern BCG in the NGC 6338 merger remains another prominent case where the direction of jet-mode feedback between two cycles changed dramatically. [ABSTRACT FROM AUTHOR]

This paper represents an effort to provide robust constraints on the galaxy–halo connection and simultaneously test the Planck ΛCDM cosmology using a fully numerical model of small-scale galaxy clustering. We explore two extensions to the standard Halo Occupation Distribution model: assembly bias, whereby halo occupation depends on both halo mass and the larger environment, and velocity bias, whereby galaxy velocities do not perfectly trace the velocity of the dark matter within the halo. Moreover, we incorporate halo mass corrections to account for the impact of baryonic physics on the halo population. We identify an optimal set of clustering measurements to constrain this "decorated" HOD model for both low- and high-luminosity galaxies in SDSS DR7. We find that, for low-luminosity galaxies, a model with both assembly bias and velocity bias provides the best fit to the clustering measurements, with no tension remaining in the fit. In this model, we find evidence for both central and satellite galaxy assembly bias at the 99% and 95% confidence levels, respectively. In addition, we find evidence for satellite galaxy velocity bias at the 99.9% confidence level. For high-luminosity galaxies, we find no evidence for either assembly bias or velocity bias, but our model exhibits significant tension with SDSS measurements. We find that all of these conclusions still stand when we include the effects of baryonic physics on the halo mass function, suggesting that the tension we find for high-luminosity galaxies may be due to a problem with our assumed cosmological model. [ABSTRACT FROM AUTHOR]

We explore how the fraction of quenched galaxies changes in groups of galaxies with respect to the distance to the center of the group, redshift, and stellar mass to determine the dominant process of environmental quenching in 0.2 < z < 0.8 groups. We use new UV data from the UVCANDELS project in addition to existing multiband photometry to derive new galaxy physical properties of the group galaxies from the zCOSMOS 20 k group catalog. Limiting our analysis to a complete sample of log (M */ M ⊙) > 10.56 group galaxies, we find that the probability of being quenched increases slowly with decreasing redshift, diverging from the stagnant field galaxy population. A corresponding analysis on how the probability of being quenched increases with time within groups suggests that the dominant environmental quenching process is characterized by slow (∼Gyr) timescales. We find a quenching time of approximately 4.91 − 1.47 + 0.91 Gyr, consistent with the slow processes of strangulation and delayed-then-rapid quenching although more data are needed to confirm this result. [ABSTRACT FROM AUTHOR]

The properties of warm-hot gas around ∼ L _* galaxies can be studied with absorption lines from highly ionized metals. We predict Ne viii column densities from cosmological zoom-in simulations of halos with masses in ∼10 ^12 and ∼10 ^13 M _☉ from the Feedback in Realistic Environments (FIRE) project. Ne viii traces the volume-filling, virial-temperature gas in ∼10 ^12 M _☉ halos. In ∼10 ^13 M _☉ halos the Ne viii gas is clumpier, and biased toward the cooler part of the warm-hot phase. We compare the simulations to observations from the COS Absorption Survey of Baryon Harbors (or CASBaH) and COS Ultraviolet Baryon Survey (or CUBS). We show that when inferring halo masses from stellar masses to compare simulated and observed halos, it is important to account for the scatter in the stellar-mass–halo-mass relation, especially at M _⋆ ≳ 10 ^10.5 M _☉ . Median Ne viii columns in the fiducial FIRE-2 model are about as high as observed upper limits allow, while the simulations analyzed do not reproduce the highest observed columns. This suggests that the median Ne viii profiles predicted by the simulations are consistent with observations, but that the simulations may underpredict the scatter. We find similar agreement with analytical models that assume a product of the halo gas fraction and metallicity (relative to solar) ∼0.1, indicating that observations are consistent with plausible circumgalactic medium temperatures, metallicities, and gas masses. Variants of the FIRE simulations with a modified supernova feedback model and/or active galactic nuclei feedback included (as well as some other cosmological simulations from the literature) more systematically underpredict Ne viii columns. The circumgalactic Ne viii observations therefore provide valuable constraints on simulations that otherwise predict realistic galaxy properties.

3C 275.1 is a blue quasar at z = 0.55522, hosting powerful outflows and residing in a complex environment. We present a serendipitously detected giant nebula surrounding 3C 275.1, which shows morphological features resembling those of objects known as “jellyfish galaxies,” with extremely long tails of ionized gas extending to 170 kpc in projection. We analyze its optical spectra taken by MUSE on the Very Large Telescope. The brighter part of this giant nebula exceeds 100 kpc, and its rotation curve does not flatten out, making it very different from those of normal spiral galaxies. This system shares some characteristics common to those formed via ram pressure stripping (RPS), yet its long narrow tails and higher ionization are unusual compared to known tails in jellyfish galaxies, not fully consistent with a simple RPS scenario. Our photoionization simulation and the inferred short recombination timescale both suggest that, besides the quasar 3C 275.1, an extra source of ionization is necessary to keep the gas ionized at such a distance from the nucleus, which could be related to RPS, tidal interaction, or active galactic nucleus outflow, providing new evidence of active dynamical interaction of a galaxy with the intracluster medium.

We study star formation (SF) quenching of satellite galaxies with M _* > 10 ^7 M _⊙ within two low-mass groups ( M _vir = 10 ^12.9 and 10 ^12.7 M _⊙ ) using the NewHorizon simulation. We confirm that satellite galaxies ( M _* ≲ 10 ^10 M _⊙ ) are more prone to quenching than their field counterparts. This quenched fraction decreases with increasing stellar mass, consistent with recent studies. Similar to the findings in cluster environments, we note a correlation between the orbital motions of galaxies within these groups and the phenomenon of SF quenching. Specifically, SF is suppressed at the group center, and for galaxies with M _* > 10 ^9.1 M _⊙ , there is often a notable rejuvenation phase following a temporary quenching period. The SF quenching at the group center is primarily driven by changes in SF efficiency and the amount of gas available, both of which are influenced by hydrodynamic interactions between the interstellar medium and surrounding hot gas within the group. Conversely, satellite galaxies with M _* < 10 ^8.2 M _⊙ experience significant gas removal within the group, leading to SF quenching. Our analysis highlights the complexity of SF quenching in satellite galaxies in group environments, which involves an intricate competition between the efficiency of SF (which depends on the dynamical state of the gas) on the one hand, and the availability of cold dense gas on the other hand. This challenges the typical understanding of environmental effects based on gas stripping through ram pressure, suggesting a need for a new description of galaxy evolution under mild environmental effects.

In this investigation, we leverage the combination of the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9, Survey Validation 3, and Year 1 data sets to estimate the conditional luminosity functions and conditional stellar mass functions (CLFs and CSMFs) of galaxies across various halo mass bins and redshift ranges. To support our analysis, we utilize a realistic DESI mock galaxy redshift survey (MGRS) generated from a high-resolution Jiutian simulation. An extended halo-based group finder is applied to both MGRS catalogs and DESI observation. By comparing the r - and z -band luminosity functions (LFs) and stellar mass functions (SMFs) derived using both photometric and spectroscopic data, we quantified the impact of photometric redshift (photo- z ) errors on the galaxy LFs and SMFs, especially in the low-redshift bin at the low-luminosity/mass end. By conducting prior evaluations of the group finder using MGRS, we successfully obtain a set of CLF and CSMF measurements from observational data. We find that at low redshift, the faint-end slopes of CLFs and CSMFs below ∼10 ^9 h ^−2 L _⊙ (or h ^−2 M _⊙ ) evince a compelling concordance with the subhalo mass functions. After correcting the cosmic variance effect of our local Universe following Chen et al., the faint-end slopes of the LFs/SMFs turn out to also be in good agreement with the slope of the halo mass function.

NGC 777 provides an example of a phenomenon observed in some group-central ellipticals, in which the temperature profile shows a central peak, despite the short central cooling time of the intragroup medium. We use deep Chandra X-ray observations of the galaxy, supported by uGMRT 400 MHz radio imaging, to investigate the origin of this hot core. We confirm the centrally peaked temperature profile and find that the entropy and cooling time both monotonically decline to low values (2.62 ${}_{-0.18}^{+0.19}$ keV cm ^2 and ${71.3}_{-13.1}^{+12.8}$ Myr, respectively) in the central ∼700 pc. Faint diffuse radio emission surrounds the nuclear point source, with no clear jets or lobes but extending to ∼10 kpc on the northwest–southeast axis. This alignment and extent agree well with a previously identified filamentary H α + [N ii ] nebula. While cavities are not firmly detected, we see X-ray surface brightness decrements on the same axis at 10–20 kpc radii, which are consistent with the intragroup medium having been pushed aside by expanding radio lobes. Any such outburst must have occurred long enough ago for lobe emission to have faded below detectability. Cavities on this scale would be capable of balancing radiative cooling for at least ∼240 Myr. We consider possible causes of the centrally peaked temperature profile, including gravitational heating of gas as the halo relaxes after a period of active galactic nucleus jet activity, and heating by particles leaking from the remnant relativistic plasma of the old radio jets.

We present HaloFlow , a new machine-learning approach for inferring the mass of host dark matter halos, M _h , from the photometry and morphology of galaxies ( https://github.com/changhoonhahn/haloflow/ ). HaloFlow uses simulation-based inference with normalizing flows to conduct rigorous Bayesian inference. It is trained on state-of-the-art synthetic galaxy images from Bottrell et al. that are constructed from the IllustrisTNG hydrodynamic simulation and include realistic effects of the Hyper Suprime-Cam Subaru Strategy Program observations. We design HaloFlow to infer M _h and stellar mass, M _* , using grizy band magnitudes, morphological properties quantifying characteristic size, concentration and asymmetry, total measured satellite luminosity, and number of satellites. We demonstrate that HaloFlow infers accurate and unbiased posteriors of M _h . Furthermore, we quantify the full information content in the photometric observations of galaxies in constraining M _h . With magnitudes alone, we infer M _h with ${\sigma }_{\mathrm{log}{M}_{h}}\sim 0.115$ and 0.182 dex for field and group galaxies. Including morphological properties significantly improves the precision of M _h constraints, as does total satellite luminosity: ${\sigma }_{\mathrm{log}{M}_{h}}\sim 0.095$ and 0.132 dex. Compared to the standard approach using the stellar-to-halo mass relation, we improve M _h constraints by ∼40%. In subsequent papers, we will validate and calibrate HaloFlow with galaxy–galaxy lensing measurements on real observational data.

Galaxy formation models within cosmological hydrodynamical simulations contain numerous parameters with nontrivial influences over the resulting properties of simulated cosmic structures and galaxy populations. It is computationally challenging to sample these high dimensional parameter spaces with simulations, in particular for halos in the high-mass end of the mass function. In this work, we develop a novel sampling and reduced variance regression method, CARPoolGP , which leverages built-in correlations between samples in different locations of high dimensional parameter spaces to provide an efficient way to explore parameter space and generate low-variance emulations of summary statistics. We use this method to extend the Cosmology and Astrophysics with machinE Learning Simulations to include a set of 768 zoom-in simulations of halos in the mass range of 10 ^13 –10 ^14.5 M _⊙ h ^−1 that span a 28-dimensional parameter space in the IllustrisTNG model. With these simulations and the CARPoolGP emulation method, we explore parameter trends in the Compton Y – M , black hole mass–halo mass, and metallicity–mass relations, as well as thermodynamic profiles and quenched fractions of satellite galaxies. We use these emulations to provide a physical picture of the complex interplay between supernova and active galactic nuclei feedback. We then use emulations of the Y – M relation of massive halos to perform Fisher forecasts on astrophysical parameters for future Sunyaev–Zeldovich observations and find a significant improvement in forecasted constraints. We publicly release both the simulation suite and CARPoolGP software package.

We investigate the group-scale environment of 15 luminous quasars (luminosity L _3000 > 10 ^46 erg s ^−1 ) from the Cosmic Ultraviolet Baryon Survey (CUBS) at redshift z ≈ 1. Using the Multi Unit Spectroscopic Explorer integral field spectrograph on the Very Large Telescope, we conduct a deep galaxy redshift survey in the CUBS quasar fields to identify group members and measure the physical properties of individual galaxies and galaxy groups. We find that the CUBS quasars reside in diverse environments. The majority (11 out of 15) of the CUBS quasars reside in overdense environments with typical halo masses exceeding 10 ^13 M _⊙ , while the remaining quasars reside in moderate-size galaxy groups. No correlation is observed between overdensity and redshift, black hole (BH) mass, or luminosity. Radio-loud quasars (5 out of 15 CUBS quasars) are more likely to be in overdense environments than their radio-quiet counterparts in the sample, consistent with the mean trends from previous statistical observations and clustering analyses. Nonetheless, we also observe radio-loud quasars in moderate groups and radio-quiet quasars in overdense environments, indicating a large scatter in the connection between radio properties and environment. We find that the most UV luminous quasars might be outliers in the stellar mass-to-halo mass relations or may represent departures from the standard single-epoch BH relations.

We use deep Hubble Space Telescope imaging to study the resolved stellar populations in BST1047+1156, a gas-rich, ultradiffuse dwarf galaxy found in the intragroup environment of the Leo I galaxy group. While our imaging reaches approximately two magnitudes below the tip of the red giant branch at the Leo I distance of 11 Mpc, we find no evidence for an old red giant sequence that would signal an extended star formation history for the object. Instead, we clearly detect the red and blue helium-burning sequences of its stellar populations, as well as the fainter blue main sequence, all indicative of a recent burst of star formation having taken place over the past 50–250 Myr. Comparing to isochrones for young metal-poor stellar populations, we infer this post-starburst population to be moderately metal-poor, with metallicity [ M/H ] in the range −1 to −1.5. The combination of a young, moderately metal-poor post starburst population and no old stars motivates a scenario in which BST1047 was recently formed during a weak burst of star formation in gas that was tidally stripped from the outskirts of the neighboring massive spiral M96. BST1047's extremely diffuse nature, lack of ongoing star formation, and disturbed H i morphology all argue that it is a transitory object, a “failing tidal dwarf” in the process of being disrupted by interactions within the Leo I group. Finally, in the environment surrounding BST1047, our imaging also reveals the old, metal-poor ([ M/H ] = − 1.3 ± 0.2) stellar halo of M96 at a projected radius of 50 kpc.

We report on the spectroscopic confirmation of a massive quiescent galaxy at z _spec = 4.53 in the COSMOS field. The object was first identified as a galaxy with suppressed star formation at z _phot ∼ 4.65 from the COSMOS2020 catalog. The follow-up spectroscopy with Keck/MOSFIRE in the K band reveals faint [O ii ] emission and the Balmer break, indicative of evolved stellar populations. We fit the spectral energy distribution using photometry and a spectrum to infer physical properties. The obtained stellar mass is high ( M _* ∼ 10 ^10.8 M _⊙ ) and the current star formation rate is more than 1 dex below that of main-sequence galaxies at z = 4.5. Its star formation history suggests that this galaxy experienced rapid quenching from z ∼ 5. The galaxy is among the youngest quiescent galaxies confirmed so far at z _spec > 3 with z _form ∼ 5.2 (200 Myr ago), which is the epoch when 50% of the total stellar mass was formed. A unique aspect of the galaxy is that it is in an extremely dense region; there are four massive star-forming galaxies at 4.4 < z _phot < 4.7 located within 150 physical kpc from the galaxy. Interestingly, three of them have virial radii that strongly overlap with that of the central quiescent galaxy (∼70 kpc), suggesting that the overdensity region is likely the highest-redshift candidate of a dense group with a spectroscopically confirmed quiescent galaxy at the center. The group provides us with a unique opportunity to gain insights into the role of the group environment in quenching at z ∼ 5, which corresponds to the formation epoch of massive elliptical galaxies in the local Universe.

Recent observations of galaxy clusters and groups with misalignments between their central active galactic nucleus jets and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet–bubble connection in cooling cores, and the processes responsible for jet realignment. To investigate the frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and groups. Using Very Long Baseline Array radio data, we measure the parsec-scale position angle of the jets, and compare it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample and selected subsets, we consistently find that there is a 30%–38% chance to find a misalignment larger than ΔΨ = 45° when observing a cluster/group with a detected jet and at least one cavity. We determine that projection may account for an apparently large ΔΨ only in a fraction of objects (∼35%), and given that gas dynamical disturbances (such as sloshing) are found in both aligned and misaligned systems, we exclude environmental perturbation as the main driver of cavity–jet misalignment. Moreover, we find that large misalignments (up to ∼90°) are favored over smaller ones (45° ≤ ΔΨ ≤ 70°), and that the change in jet direction can occur on timescales between one and a few tens of Myr. We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we discuss several engine-based mechanisms that may cause these dramatic changes.

Possibilities to detect hostless supernova remnants (hl-SNR) in intergalactic medium using the 1 GHz band of the Square Kilometre Array (SKA) are discussed. The optical detection rate of the hl-SN constrained from the Sloan Digital Sky Survey is used to predict a number of detectable hl-SNRs in the radio band. With an anticipated detection sensitivity ( ∼ 1 μ Jy) and angular resolution ( < 1 ′ ′ ) with the SKA, a significant number of hl-SNR are expected to get detected in the nearby galaxy groups, such as local group, Virgo, Fornax and Eridanus. A few very luminous hl-SNR may also be detected in the Coma cluster and other rich galaxy clusters up to about 100 Mpc distance. The identification of individual SNRs against other background radio sources will require sub-arcsec angular resolution at 1 GHz to resolve the characteristic circular morphology of the radio SNRs in nearby groups. At larger distances, where individual SNR cannot be resolved, a population of hl-SNR may also be constrained statistically in a small region, by estimating excess unresolved radio sources without a known optical host in a group or cluster, compared to the number density of the background radio sources at μ Jy flux level. [ABSTRACT FROM AUTHOR]

The boundaries of galaxy groups and clusters are defined by the interplay between the Newtonian attractive force and the decoupling from the local expansion of the Universe. This work extends the definition of a zero radial acceleration surface (ZRAS) and the turnaround surface (TS) for a general distribution of the masses in an expanding background, governed by the cosmological constant. We apply these definitions to different galaxy groups in the local Universe, mapping these groups up to ten megaparsec distances. We discuss the dipole and the quadrupole rate for the Local Group of Galaxies and the implementations on the Hubble diagram correction and galaxy groups virialization. With these definitions, we present the surfaces showing the interplay between the local expansion vs the local Newtonian attraction for galaxy groups in the local Universe. Further, we estimate the masses of different galaxy groups and show that the inclusion of the Cosmological Constant in the analysis predicts these masses to be higher by 5-10%. For instance the Local Group of galaxies is estimated to be (2.47 ± 0.08) ⋅ 10 12 M ⊙. For the groups with enough tracers close to the TS, the contribution of the Cosmological Constant makes the masses to be even higher. The results show the importance of including the local cosmic expansion in analyzing the Cosmic Flow of the local Universe. [ABSTRACT FROM AUTHOR]

The r-band of the Sloan Digital Sky Survey (SDSS) for 17,924 brightest cluster galaxies (BCGs) in clusters and groups within 0.02 ⩽ z ⩽ 0.20 are used to study possible environmental relations affecting the nature of these galaxies. We find a correlation between BCGs physical properties (the effective radius (Re), absolute magnitude and central velocity dispersion (σ0)) and their host groups and clusters velocity dispersion (σcl). This type of relations suggests that the most massive groups or clusters host larger central galaxies. On the other hand, the σ0/σcl ratio as a function of σcl is consistent with [10].

We report the discovery of giant (50−100 kpc) [O ii ] emitting nebulae with MUSE in the field of TXS 0206−048, a luminous quasar at z = 1.13. “Down-the-barrel” UV spectra of the quasar show absorption at velocities coincident with those of the extended nebulae, enabling new insights into inflows and outflows around the quasar host. One nebula exhibits a filamentary morphology extending over 120 kpc from the halo toward the quasar and intersecting with another nebula surrounding the quasar host with a radius of 50 kpc. This is the longest cool filament observed to date and arises at higher redshift and in a less massive system than those in cool-core clusters. The filamentary nebula has line-of-sight velocities >300 km s ^−1 from nearby galaxies but matches that of the nebula surrounding the quasar host where they intersect, consistent with accretion of cool intergalactic or circumgalactic medium or cooling hot halo gas. The kinematics of the nebulae surrounding the quasar host are unusual and complex, with redshifted and blueshifted spiral-like structures. The emission velocities at 5−10 kpc from the quasar match those of inflowing absorbing gas observed in UV spectra of the quasar. Together, the extended nebulae and associated redshifted absorption represent a compelling case of cool, filamentary gas accretion from halo scales into the extended interstellar medium and toward the nucleus of a massive quasar host. The inflow rate implied by the combined emission and absorption constraints is well below levels required to sustain the quasar’s radiative luminosity, suggesting anisotropic or variable accretion.

We have undertaken a near-IR weak-lensing (NIRWL) analysis of the CANDELS HST/WFC3-IR F160W observations. With the Gaia proper motion–corrected catalog as an astrometric reference, we updated the astrometry of the five CANDELS mosaics and achieved an absolute alignment within 0.″02 ± 0.″02, on average, which is a factor of several superior to existing mosaics. These mosaics are available to download ( https://drive.google.com/drive/folders/1k9WEV3tBOuRKBlcaTJ0-wTZnUCisS__r ). We investigated the systematic effects that need to be corrected for weak-lensing measurements. We find that the largest contributing systematic effect is caused by undersampling. We find a subpixel centroid dependence on the PSF shape that causes the PSF ellipticity and size to vary by up to 0.02 and 3%, respectively. Using the UDS as an example field, we show that undersampling induces a multiplicative shear bias of −0.025. We find that the brighter-fatter effect causes a 2% increase in the size of the PSF and discover a brighter-rounder effect that changes the ellipticity by 0.006. Based on the small range of slopes in a galaxy’s spectral energy distribution (SED) within the WFC3-IR bandpasses, we suggest that the impact of the galaxy SED on the PSF is minor. Finally, we model the PSF of WFC3-IR F160W for weak lensing using a principal component analysis. The PSF models account for temporal and spatial variations of the PSF. The PSF corrections result in residual ellipticities and sizes, ∣ de _1 ∣ < 0.0005 ± 0.0003, ∣ de _2 ∣ < 0.0005 ± 0.0003, and ∣ dR ∣ < 0.0005 ± 0.0001, that are sufficient for the upcoming NIRWL search for massive overdensities in the five CANDELS fields.

We present a four-step group-finding algorithm for the Gas in Galaxy Groups (G3) initiative, a spin-off of the z ∼ 0 REsolved Spectroscopy Of a Local VolumE (RESOLVE) and Environmental COntext (ECO) surveys. In preparation for future comparisons to intermediate redshift (e.g., the LADUMA survey), we design the group finder to adapt to incomplete, shallow, or nonuniform data. We use mock catalogs to optimize the group finder’s performance. Compared to friends-of-friends (with false-pair splitting), the G3 algorithm offers improved completeness and halo-mass recovery with minimal loss of purity. Combining it with the volume-limited H i census data for RESOLVE and ECO, we examine the H i content of galaxy groups as a function of group halo mass. Group-integrated H i mass M _H I,grp rises monotonically over halo masses M _halo ∼ 10 ^11 –10 ^14.5 M _⊙ , pivoting in slope at M _halo ∼ 10 ^11.4 M _⊙ , the gas-richness threshold scale. We present the first measurement of the scatter in this relation, which has a median of ∼0.3 dex and is asymmetric toward lower M _H I,grp . We discuss interesting tensions with theoretical predictions and prior measurements of the M _H I,grp – M _halo relation. In an appendix, we release RESOLVE DR4 and ECO DR3, including updates to survey redshifts, photometry, and group catalogs, as well as a major expansion of the ECO H i inventory with value-added data products.

We investigate the fraction of quenched satellite galaxies in host galaxy groups and clusters using TNG300 in the IllustrisTNG cosmological magnetohydrodynamical simulations. The simulations show that most satellites are quenched after they fall into their final hosts, and that post-processing is a more dominant mechanism of galaxy quenching than pre-processing. We find that the fraction of quenched satellites at z = 0 increases with host mass, which implies that more massive hosts have higher quenching efficiency because they have more massive groups infalling. Furthermore, we find that hosts that have many early-infall satellites show a higher fraction of quenched satellites at z = 0 than those that have many late-infall satellites, which results in a scatter of the quenched fraction of satellites in a given mass range of hosts at z = 0. Our results highlight the significance of the mass of hosts and the different infall times of satellites in understanding galaxy quenching.

We carried out deep mapping observations of the atomic hydrogen (H i ) 21 cm line emission in a field centered on the famous galaxy group Stephan's Quintet (SQ), using the Five-hundred-meter Aperture Spherical Telescope (FAST) equipped with a 19-beam receiver. The final data cube reaches an H i column density sensitivity of 5 σ = 2.1 × 10 ^17 cm ^−2 per 20 km s ^−1 channel with an angular resolution of 4.′0. The discovery of a large diffuse feature of the H i emission in the outskirts of the intragroup medium of SQ was reported in a previous paper (Xu et al.). Here we present a new study of the total H i emission of SQ and the detection of several neighboring galaxies, exploiting the high sensitivity and the large sky coverage of the FAST observations. A total H i mass of M _H I = 3.48 ± 0.35 × 10 ^10 M _☉ is found for SQ, which is significantly higher than previous measurements in the literature. This indicates that, contrary to earlier claims, SQ is not H i deficient. The excessive H i gas is mainly found in the velocity ranges of 6200–6400 km s ^−1 and 6800–7000 km s ^−1 , which were undetected in previous observations that are less sensitive than ours. Our results suggest that the “missing H i ” in compact groups may be hidden in the low-density diffuse neutral gas instead of in the ionized gas.

Chemical elements in the hot medium permeating early-type galaxies, groups, and clusters make such objects an excellent laboratory for studying metal enrichment and cycling processes on the largest scales of the universe. Here, we report the analysis by the XMM-Newton Reflection Grating Spectrometer of 14 early-type galaxies, including the well-known brightest cluster galaxies of Perseus, for instance. The spatial distribution of the O/Fe, Ne/Fe, and Mg/Fe ratios is generally flat in the central 60″ regions of each object, irrespective of whether or not a central Fe abundance drop has been reported. Common profiles between noble gas and normal metal suggest that the dust depletion process does not work predominantly in these systems. Therefore, observed abundance drops are possibly attributed to other origins, such as systematics in the atomic codes. Giant systems with a high ratio of gas mass to luminosity tend to hold a hot gas (∼2 keV) yielding the solar N/Fe, O/Fe, Ne/Fe, Mg/Fe, and Ni/Fe ratios. Contrarily, light systems in a sub-keV temperature regime, including isolated or group-centered galaxies, generally exhibit supersolar N/Fe, Ni/Fe, Ne/O, and Mg/O ratios. We find that the latest supernova nucleosynthesis models fail to reproduce such a supersolar abundance pattern. Possible systematic uncertainties contributing to these high abundance ratios of cool objects are also discussed in tandem with the crucial role of future X-ray missions.

We combine James Webb Space Telescope (JWST) and Hubble Space Telescope imaging with Atacama Large Millimeter Array CO(2–1) spectroscopy to study the highly turbulent multiphase intergalactic medium (IGM) in Stephan’s Quintet on 25–150 pc scales. Previous Spitzer observations revealed luminous H _2 line cooling across a 45 kpc-long filament, created by a giant shock wave, following the collision with an intruder galaxy, NGC 7318b. We demonstrate that the Mid-Infrared Instrument/F1000W/F770W filters are dominated by 0–0 S(3) H _2 and a combination of polycyclic aromatic hydrocarbon and 0–0 S(5) H _2 emission. These observations reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions, and likely destruction/recycling within different phases of the IGM. In 1 kpc-scaled structure, warm H _2 was seen to form a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H _2 . In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H _2 suggesting a cloud–cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H _2 lines throughout Stephan’s Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. A full picture of the diverse kinematics and excitation of the warm H _2 will require future JWST mid-IR spectroscopy. The current observations reveal the rich variety of ways that different gas phases can interact with one another.

We investigate the environmental dependence of the gas-phase metallicity for galaxies at z = 0 to z ≳ 2 and the underlying physical mechanisms driving this dependence using state-of-the-art cosmological hydrodynamical simulations. We find that, at fixed stellar mass, central galaxies in massive halos have lower gas-phase metallicity than those in low-mass halos, while satellite galaxies residing in more massive halos are more metal-rich. The combined effect is that massive galaxies are more metal-poor in massive halos and low-mass galaxies are more metal-rich in massive halos. By inspecting the environmental dependence of other galaxy properties, we identify that the accretion of low-metallicity gas is responsible for the environmental dependence of central galaxies at high z , whereas the AGN feedback processes play a crucial role at low z . For satellite galaxies, we find that both the suppression of gas accretion and the stripping of existing gas are responsible for their environmental dependence, with negligible effect from the AGN feedback. Finally, we show that the difference of gas-phase metallicity as a function of stellar mass between protocluster and field galaxies agrees with recent observational results, for example from the MAMMOTH-Grism survey.

This paper represents an effort to provide robust constraints on the galaxy–halo connection and simultaneously test the Planck ΛCDM cosmology using a fully numerical model of small-scale galaxy clustering. We explore two extensions to the standard Halo Occupation Distribution model: assembly bias, whereby halo occupation depends on both halo mass and the larger environment, and velocity bias, whereby galaxy velocities do not perfectly trace the velocity of the dark matter within the halo. Moreover, we incorporate halo mass corrections to account for the impact of baryonic physics on the halo population. We identify an optimal set of clustering measurements to constrain this “decorated” HOD model for both low- and high-luminosity galaxies in SDSS DR7. We find that, for low-luminosity galaxies, a model with both assembly bias and velocity bias provides the best fit to the clustering measurements, with no tension remaining in the fit. In this model, we find evidence for both central and satellite galaxy assembly bias at the 99% and 95% confidence levels, respectively. In addition, we find evidence for satellite galaxy velocity bias at the 99.9% confidence level. For high-luminosity galaxies, we find no evidence for either assembly bias or velocity bias, but our model exhibits significant tension with SDSS measurements. We find that all of these conclusions still stand when we include the effects of baryonic physics on the halo mass function, suggesting that the tension we find for high-luminosity galaxies may be due to a problem with our assumed cosmological model.

The galaxy group NGC 6338 is one of the most violent group–group mergers known to date. While the central dominant galaxies rush at each other at 1400 km s ^−1 along the line of sight, with dramatic gas heating and shock fronts detected, the central gas in the BCGs remains cool. There are also indications of feedback from active galactic nuclei, and neither subcluster core has been disrupted. With our deep radio uGMRT data at 383 and 650 MHz, we clearly detect a set of large, old lobes in the southern BCG coinciding with the X-ray cavities, while the northern and smaller BCG appears slightly extended in the radio. The southern BCG also hosts a smaller younger set of lobes perpendicular to the larger lobes, but also coinciding with the inner X-ray cavities and matching the jet direction in the parsec-resolution VLBA image. Our spectral analysis confirms the history of two feedback cycles. The high radio frequency analysis classifies the compact source in the southern BCG with a power law, while ruling out a significant contribution from accretion. The radio lightcurve over three decades shows a change about 10 yr ago, which might be related to ongoing feedback in the core. The southern BCG in the NGC 6338 merger remains another prominent case where the direction of jet-mode feedback between two cycles changed dramatically.

We use the DR9 of the DESI legacy imaging survey and SDSS galaxy groups to measure the conditional luminosity function (CLF) for groups with halo mass M _h ≥ 10 ^12 M _⊙ and redshift 0.01 ≤ z ≤ 0.08, down to a limiting r -band magnitude of M _r = −10 to −12. For given halo masses we measure the CLF for the total populations and for the red and blue populations classified using the ( g − z ) color. We find a clear faint-end upturn in the CLF of red satellites, with a slope α ≈ −1.8, which is almost independent of halo mass. This faint-end upturn is not seen for the blue and total populations. Our stellar population synthesis modeling shows that ( g − z ) provides a clean red/blue division and that red group galaxies defined by ( g − z ) are all dominated by old stellar populations. The fraction of old galaxies as a function of galaxy luminosity shows a minimum at M _r ∼ −18, corresponding to M _* ∼ 10 ^9.5 M _⊙ . This scale is independent of halo mass and is comparable to the characteristic luminosity at which galaxies show a dichotomy in surface brightness and size, suggesting that the dichotomy in the old fraction and in galaxy structure may have a common origin. The rising of the old fraction at the faint end for Milky Way (MW)−sized halos is in good agreement with the quenched fraction measured for the MW/M31 system and from the ELVES survey. We discuss the implications of our results for the formation and evolution of low-mass galaxies and for the stellar mass functions of low-mass galaxies to be observed at high redshift.

NGC 4839 is the brightest galaxy (cD) of the NGC 4839 group at R ≈ 1 Mpc in the southwest of the Coma cluster, which is known to be falling into Coma. However, it has been controversial whether it is in the first phase of infall or in the second phase of infall after passing the Coma center. We present a wide field study of globular clusters (GCs) in NGC 4839 and its environment based on Hyper Suprime-Cam gr images in the Subaru archive. We compare the GC system of NGC 4839 with that of NGC 4816, which is the brightest member (S0) of the nearby group and lies at a similar distance in the west from the Coma center. Interestingly the spatial distribution of the GCs in NGC 4839 is significantly more compact than that of the GCs in NGC 4816. In addition, the radial number density profile of the GCs in NGC 4839 shows an abrupt drop at R _N4839 ≈ 80 kpc, while that of the GCs in NGC 4816 shows a continuous slow decline even in the outer region at 80 < R _N4816 < 500 kpc. The effective radius of the NGC 4839 GC system is about 3 times smaller than that of the NGC 4816 GC system. This striking difference can be explained if NGC 4839 lost a significant fraction of the GCs in its outskirt when it passed through Coma. This supports strongly the second-infall scenario where the NGC 4839 passed the Coma center about 1.6 Gyr ago, and began the second infall after reaching the apocenter in the southwest recently.

We explore how the fraction of quenched galaxies changes in groups of galaxies with respect to the distance to the center of the group, redshift, and stellar mass to determine the dominant process of environmental quenching in 0.2 < z < 0.8 groups. We use new UV data from the UVCANDELS project in addition to existing multiband photometry to derive new galaxy physical properties of the group galaxies from the zCOSMOS 20 k group catalog. Limiting our analysis to a complete sample of log ( M _* / M _⊙ ) > 10.56 group galaxies, we find that the probability of being quenched increases slowly with decreasing redshift, diverging from the stagnant field galaxy population. A corresponding analysis on how the probability of being quenched increases with time within groups suggests that the dominant environmental quenching process is characterized by slow (∼Gyr) timescales. We find a quenching time of approximately ${4.91}_{-1.47}^{+0.91}$ Gyr, consistent with the slow processes of strangulation and delayed-then-rapid quenching although more data are needed to confirm this result.

We present an extensive catalog of 5405 early-type dwarf (dE) galaxies located in the various environments, i.e., clusters, groups, and fields, of the local universe ( z < 0.01). The dEs are selected through visual inspection of the Legacy survey’s g – r – z combined tricolor images. The inspected area, covering a total sky area of 7643 deg ^2 , encompasses two local clusters (Virgo and Fornax), 265 groups, and the regions around 586 field galaxies of M _K < −21 mag. The catalog aims to be one of the most extensive and publicly accessible collections of data on dEs, despite its complex completeness limits, which may not accurately represent its statistical completeness. The strength of the catalog lies in the morphological characteristics, including nucleated, tidal, and ultradiffuse dEs. The two clusters contribute nearly half (2437 out of 5405) of the dEs, and the 265 groups contribute 2103 dEs. There are 864 dEs in 586 fields, i.e., ∼1.47 dEs per field. Using a standard definition commonly used in literature, we identify 100 ultradiffuse galaxies (UDGs), which compose ∼2% of the dE population. We find that 40% of our sample dEs harbor a central nucleus, and among the UDG population, a majority (79%) are nonnucleated. About 1.3% of dEs suffer from ongoing tidal disturbance by nearby massive galaxies, and only 0.03% show a sign of recent dwarf–dwarf mergers. The association between dEs and their nearest bright neighbor galaxies suggests that dEs are more likely created where their neighbors are non-star-forming ones.

The intersections between a spherical shell and the faces of Voronoi polyhedrons are numerically evaluated. The nodes of these intersections are the points that share the same distances from three nuclei. The nodes are assumed to be the places where we will find clusters of galaxies. The cosmological environment is given by the coupling between the number of galaxies as function of the redshift and the LCDM cosmology.

Based on archival Hubble Space Telescope images, we have performed stellar photometry for the spiral Seyfert galaxy NGC 1672 located in the Dorado (Goldfish) galaxy group. The distance to this galaxy measured by the TRGB method ( Mpc) has shown that NGC 1672 does enter into the Dorado group. We have identified stars of various ages and luminosities on the Hertzsprung–Russell diagrams and studied their distribution over the body of the galaxy. Intense star formation and asymmetry in the distribution of young stars point to the interaction of NGC 1672 with the close galaxy NGC 1688 located at a distance of 200 kpc. We have found that several young star clusters contain stars of very high luminosities (as high as ) that can be defined as massive hypergiants. [ABSTRACT FROM AUTHOR]