We investigate cool HI gas traced by Lyman series absorption around 256 galaxies at z approximate to 0.48 (median stellar mass, log10 ( M-*/M-circle dot) = 8.7) using 15 background quasars (median impact parameter, D = 140 pkpc), as part of the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). We find that the HI column density (N(H I )) profile around isolated star-forming galaxies spanning approximate to 3 dex in M-* is well described by a power law with slope approximate to -3 when expressed as a function of normalized impact parameter D / R-vir. The HI covering fraction (kappa) within the virial radius for log(10)(N(H I)/cm(-2)) = 14 is significantly lower in high-mass passive galaxies than in isolated star-forming galaxies. The kappa-profile of isolated star-forming galaxies suggests a characteristic size of the H I-rich CGM of approximate to 1.5 R-vir across the stellar mass range. The mean HI mass in the outer CGM (0.3-1 R-vir) increases with M-*, ranging from approximate to 10(5.0) to 10(6.6) M-circle dot. The b-parameters of the strongest HI components correlate and anticorrelate with specific star-formation rate (sSFR) and mass, respectively, with > 2 sigma significance. Broad Ly alpha absorbers (BLAs) with b > 60 km s(-1) are predominantly associated with high-mass galaxies, likely tracing the warm-hot phase of the CGM. The velocity centroids of H I components indicate that absorbers at D < R-vir are largely consistent with being gravitationally bound to their galaxies, independent of stellar mass. Finally, leveraging approximate to 3000 galaxies from the wide-field Magellan follow-up of six MUSEQuBES fields, we find that non-isolated galaxies exhibit an H I-rich environment extending roughly three times farther than in isolated counterparts.

In this Letter, we investigate the turbulence and energy injection in the extended nebulae surrounding two luminous obscured quasars, WISEA J100211.29+013706.7 ( z = 1.5933) and SDSS J165202.64+172852.3 ( z = 2.9489). Utilizing high-resolution data from the NIRSpec integral field unit onboard the James Webb Space Telescope, we analyze the velocity fields of line-emitting gas in and around these quasars and construct the second-order velocity structure functions (VSFs) to quantify turbulent motions across different spatial scales. Our findings reveal a notable flattening in the VSFs from ≈ 3 kpc up to a scale of 10–20 kpc, suggesting that energy injection predominantly occurs at a scale ≲ 10 kpc, likely powered by quasar outflows and jet-driven bubbles. The extended spatial range of flat VSFs may also indicate the presence of multiple energy injection sources at these scales. For J1652, the turbulent energy in the host interstellar medium (ISM) is significantly higher than in tidally stripped gas, consistent with the expectation of active galactic nucleus (AGN) activities stirring up the host ISM. Compared to the VSFs observed on spatial scales of 10–50 kpc around lower-redshift UV-bright quasars, these obscured quasars exhibit higher turbulent energies in their immediate surroundings, implying different turbulence drivers between the ISM and halo-scale gas. Future studies with an expanded sample are essential to elucidate further the extent and the pivotal role of AGNs in shaping the gas kinematics of host galaxies and beyond.

We present a detailed study of the kinematics of O vi-bearing gas around 60 low-mass (median log(10)(M-star/M-circle dot) = 8.9) galaxies at low redshift (0.1 < z < 0.7) using background quasars (median impact parameter approximate to 115 kpc) as part of the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). We find that the majority of the O vi absorbers detected within the virial radius have line-of-sight velocities smaller than the escape velocities and are thus consistent with being gravitationally bound, irrespective of the halo mass. However, the fraction of such absorbers declines at larger impact parameters. The Doppler b parameter and the velocity width (Delta v(90)) of the O vi absorbers exhibit large scatter inside the virial radius of the host galaxies, but the scatter declines sharply at impact parameter D greater than or similar to 2R(vir). For high-mass galaxies ( log(10)(M-star/M-circle dot) > 9), O vI absorption displays a larger kinematic spread, quantified by the pixel-velocity two-point correlation function (TPCF). However, the difference becomes marginal when the pixel velocities are scaled by the galaxies' circular velocities. We do not find any significant difference between the TPCF of isolated and group galaxies when the stellar mass is controlled for. A significant fraction of groups (4/6) with four or more member galaxies do not show any detectable O vi absorption, likely due to the passive nature of the nearest galaxies.

This paper presents an updated framework for studying the ionizing conditions and elemental abundances of photoionized, metal-enriched quasar absorption systems. The standard assumption of ionization equilibrium invoked in absorption line analyses requires gas to cool on longer timescales than ionic recombination ( tcool≫trec). However, this assumption may not be valid at high metallicities due to enhanced cooling losses. This work presents a suite of time-dependent photoionization (TDP) models that self-consistently solve for the ionization state of rapidly cooling gas irradiated by the extragalactic ultraviolet background (UVB). The updated framework explores various revised UVBs from recent studies, a range of initial temperatures, and different elemental abundance patterns to quantify the effects of TDP on the observed ion fractions. A metal-enriched ( [α/H]=0.6−0.1+0.2) absorption system at z∼1 previously studied using photoionization equilibrium (PIE) models is re-examined under the TDP framework. The main findings are as follows: (1) varying prescriptions for the underlying UVB or change TDP ion fractions by up to a factor of three and ten respectively, but the adopted relative elemental abundance pattern affects ion fractions by at most 40%; (2) the inferred gas densities are consistent between PIE and TDP, but under TDP solar metallicity cannot be ruled out at more than 2- σ significance and a non-solar [C/ α] ≈0.25 is robustly constrained from the observed relative ion abundances. Extending the TDP analyses to a larger sample of super-solar absorption components with high signal-to-noise absorption spectra is needed to quantify the fraction of metal absorbers originating in rapid cooling gas.

Galaxies are part of a vast cosmic ecosystem, embedded in an extensive gaseous reservoir that regulates their growth by providing the necessary fuel for star formation while preserving a fossil record of past interactions, outflows, and feedback processes. The circumgalactic medium (CGM) contains multiphase gas spanning a broad dynamic range in spatial scale, density, and temperature, with its thermodynamic and chemical properties deeply linked to the star formation histories of galaxies. As a rich laboratory for studying gas physics, the CGM offers unique insights into the processes governing gas cooling, heating, and material transfer between galaxies and their surroundings. Chemical tagging, based on the relative abundances of multiple elements, serves as a powerful timing tool to trace the origin of the gas and connect the stars in the interstellar medium (ISM) to the diffuse CGM. Developing a complete understanding of the CGM and its cosmic evolution requires multi-wavelength observational tools, ranging from X-ray, UV/optical, and sub-mm to radio, to probe this diffuse gas in both absorption and emission.

We present a study of O vi -bearing gas around 247 low-mass (median log 10 ( M ⋆ / M ⊙ ) = 8.7) galaxies at low redshifts (0.1 < z < 0.7) using background quasars as part of the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). We find that the average O vi column density, log 10 N ( O VI ) / cm − 2 = 14.1 4 − 0.10 + 0.09 , measured within the virial radius for our sample, is significantly lower than for L * galaxies. Combining 253 star-forming galaxies (mostly more massive) from the literature with 176 star-forming galaxies from MUSEQuBES, we find that both N ( O VI ) and the average covering fraction peak at log 10 ( M ⋆ / M ⊙ ) ≈ 9.5. The virial temperature corresponding to this stellar mass is ideal for O vi production via collisional ionization. However, we argue that photoionization and/or nonequilibrium processes are necessary to produce the O vi associated with low-mass, dwarf galaxies ( log 10 ( M ⋆ / M ⊙ ) < 9). The average O vi mass within the virial radius of dwarf galaxies is measured to be 1 0 5 . 2 − 0.1 + 0.1 M ⊙ . The characteristic normalized impact parameter ( D / R vir ) at which the O vi covering fraction drops to half of its peak value is largest (≈1.1) for galaxies with stellar mass log 10 ( M ⋆ / M ⊙ ) ≈ 9.5. We report the presence of a highly ionized metal floor with log 10 N ( O VI ) / cm − 2 = 13.2 outside the virial radius of dwarf galaxies inferred from median spectral stacking.

With a new joint-deconvolution pipeline, we combine the single-dish and interferometric atomic hydrogen (H i ) data of M51 observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) (FEASTS program) and the Very Large Array (VLA) (THINGS). The product data cube has a typical line width of 13 km s ^−1 and a 2 σ line-of-sight (LOS) sensitivity of H i column density N _H _i ∼ 3.2 × 18 cm ^−2 at a spatial resolution of ∼18″ (∼0.7 kpc). Among the H i detected LOSs extending to ∼50 kpc, ∼89% consist of diffuse H i only, which is missed by previous VLA observations. The distribution of dense H i is reproduced by previous hydrodynamical simulations of this system, but the diffuse component is not, likely due to unresolved physics related to the interaction between the circumgalactic and interstellar media. With simple models, we find that these low N _H _i structures could survive the background ultraviolet photoionization, but are susceptible to the thermal evaporation. We find a positive correlation between LOS velocity dispersion ( σ _v ) and N _H _i with a logarithmic index of ∼0.5. Based on existing turbulent mixing layer (TML) theories and simulations, we propose a scenario of hot gas cooling and accreting onto the disk through a TML, which could reproduce the observed power index of ∼0.5. We estimate the related cooling and accretion rates to be roughly one-third to two-thirds of the star formation rate. A typical column density of diffuse H i (∼10 ^19 cm ^−2 ) can be accreted within 300 Myr, the interaction timescale previously estimated for the system. Such a gas accretion channel has been overlooked before, and may be important for gas-rich interacting systems and for high-redshift galaxy evolution.

The hydrogen Lyman-alpha (Ly α) emission line, the brightest spectral feature of a photoionized gas, is considered an indirect tracer of the escape of Lyman continuum (LyC) photons, particularly when the intergalactic medium is too opaque for direct detection. However, resonant scattering complicates interpreting the empirical properties of Ly α photons, necessitating radiative transfer simulations to capture their strong coupling with underlying gas kinematics. In this study, we leverage the exceptional spatial resolution from strong gravitational lensing to investigate the connection between Ly α line profiles and LyC leakage on scales of a few 100 pc in the Sunburst Arc galaxy at z∼2.37. New optical echelle spectra obtained using Magellan MIKE show that both the LyC leaking and non-leaking regions exhibit a classic double-peak Ly α feature with an enhanced red peak, indicating outflows at multiple locations in the galaxy. Both regions also show a central Gaussian peak atop the double peaks, indicating directly escaped Ly α photons independent of LyC leakage. We introduce a machine learning-based method for emulating Ly α simulations to quantify intrinsic dynamics ( σint), neutral hydrogen column density ( NHI), outflow velocity ( vexp), and effective temperature ( T) across continuous parameter spaces. By comparing the spatially and spectrally resolved Ly α lines in Sunburst, we argue that the directly escaped Ly α photons originate in a volume-filling, warm ionized medium spanning ∼1 kpc, while the LyC leakage is confined to regions of ≲200 pc. These sub-kpc variations in Ly α profiles highlight the complexity of interpreting integrated properties in the presence of inhomogeneous mixtures of gas and young stars, emphasizing the need for spatially and spectrally resolved observations of distant galaxies.

We present the H i surface density (Sigma(HI)) radial distributions based on total-power HI images obtained by FAST in the FEASTS program, for 35 galaxies with inclinations lower than 72 degrees. We derive the H I radius R-001, which is the radius for the 0.01 M-circle dot pc(-2) (similar to 10(18.1) cm(-2)) isodensity level, 100 times deeper than the 1 M-circle dot pc(-2) level previously commonly used to measure R-1. The profile shapes show a large diversity at a given radius in units of kpc, group virial radius, and R-1, but they align more tightly with the radius normalized by R-001. The universal HI profile has a scatter of similar to 0.2 dex and a scale length of similar to 0.11R(001) in the outer region. We derive a new R-001-M-MI relation, which has a scatter of 0.03 dex and a similar slope of similar to 0.5 to the previously known R-1-M-HI relation. Excluding strongly tidal-interacting galaxies, the ratio R-001/R-1 (anti)correlates strongly and significantly with the HI-to-stellar mass ratio and specific star formation rate, but not with the stellar mass, M-HI, dark matter mass, or star formation rate. The strongly tidal-interacting galaxies tend to show deviations from these trends and have the most flattened profiles. These results imply that, in the absence of major tidal interactions, physical processes must cooperate so that Sigma(H) (I) distributes in a self-similar way in the outer region down to the 0.01 M-circle dot pc(-2) level. Moreover, they may drive gas flows in such a way that H I-richer galaxies have H I disks that not only extend further but also transport HI inward more efficiently from R-001 to R-1.

We report the discovery of large ionized, [O II] emitting circumgalactic nebulae around the majority of thirty UV luminous quasars at $z=0.4-1.4$ observed with deep, wide-field integral field spectroscopy (IFS) with the Multi-Unit Spectroscopy Explorer (MUSE) by the Cosmic Ultraviolet Baryon Survey (CUBS) and MUSE Quasar Blind Emitters Survey (MUSEQuBES). Among the 30 quasars, seven (23%) exhibit [O II] emitting nebulae with major axis sizes greater than 100 kpc, twenty greater than 50 kpc (67%), and 27 (90%) greater than 20 kpc. Such large, optically emitting nebulae indicate that cool, dense, and metal-enriched circumgalactic gas is common in the halos of luminous quasars at intermediate redshift. Several of the largest nebulae exhibit morphologies that suggest interaction-related origins. We detect no correlation between the sizes and cosmological dimming corrected surface brightnesses of the nebulae and quasar redshift, luminosity, black hole mass, or radio-loudness, but find a tentative correlation between the nebulae and rest-frame [O II] equivalent width in the quasar spectra. This potential trend suggests a relationship between ISM content and gas reservoirs on CGM scales. The [O II]-emitting nebulae around the $z\approx1$ quasars are smaller and less common than Ly$\alpha$ nebulae around $z\approx3$ quasars. These smaller sizes can be explained if the outer regions of the Ly$\alpha$ halos arise from scattering in more neutral gas, by evolution in the cool CGM content of quasar host halos, by lower-than-expected metallicities on $\gtrsim50$ kpc scales around $z\approx1$ quasars, or by changes in quasar episodic lifetimes between $z=3$ and $1$.

The shallow potential wells of star-forming dwarf galaxies make their surrounding circumgalactic and intergalactic medium (CGM/IGM) sensitive laboratories for studying the inflows and outflows thought to regulate galaxy evolution. We present new absorption-line measurements in quasar sight lines, probing within projected distances of <300 kpc from 91 star-forming field dwarf galaxies with a median stellar mass of logM(star)/M-circle dot approximate to 8.3 at 0.077 < z < 0.73, from the Cosmic Ultraviolet Baryon Survey (CUBS). In this redshift range, the CUBS quasar spectra cover a suite of transitions including H i, low, and intermediate metal ions (e.g., C ii, Si ii, C iii, and Si iii), and highly ionized O vi. This CUBS-Dwarfs survey enables constraints with samples nine times larger than past dwarf CGM/IGM studies with similar ionic coverage. We find that low and intermediate ionization metal absorption is rare around dwarf galaxies, consistent with previous surveys of local dwarfs. In contrast, highly ionized O vi is commonly observed in sight lines that pass within the virial radius of a dwarf, and O vi detection rates are nonnegligible at projected distances of 1-2x the virial radius. Based on these measurements, we estimate that the O vi-bearing phase of the CGM/IGM accounts for a dominant share of the metal budget of dwarf galaxies. The absorption kinematics suggest that a relatively modest fraction of the O vi-bearing gas is formally unbound. Together, these results imply that low-mass systems at z less than or similar to 1 effectively retain a substantial fraction of their metals within the nearby CGM and IGM.

This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲ z ≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both O vi and Ne viii absorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs at z QSO ≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated O vi λ λ 1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s−1, while the rest show no trace of O vi to a detection limit of log N OVI / cm − 2 ≈ 13.7 . Meanwhile, only five galaxies or galaxy groups exhibit the Ne viii λ λ 770, 780 doublet absorption, down to a limiting column density of log N NeVIII / cm − 2 ≈ 14.0 . These O vi- and Ne viii-bearing halos reside in different galaxy environments with stellar masses ranging from log M star / M ⊙ ≈ 8 to ≈11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with log M star / M ⊙ ≈ 9 – 11 show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of O vi absorption is broad with σ υ > 40 km s−1 for galaxies of log M star / M ⊙ > 9 within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by O vi and Ne viii is suggested to be the dominant phase in sub-L* galaxies with log M star / M ⊙ ≈ 9 – 10 based on their high ionization fractions in the CGM.

Turbulent motions in the circumgalactic medium play a critical role in regulating the evolution of galaxies, yet their detailed characterization remains elusive. Using two-dimensional velocity maps constructed from spatially extended [O ii ] and [O iii ] emission, Chen et al. measured the velocity structure functions (VSFs) of four quasar nebulae at z ≈ 0.5–1.1. One of these exhibits a spectacular Kolmogorov relation. Here, we carry out an ensemble study using an expanded sample incorporating four new nebulae from three additional quasi-stellar object (QSO) fields. The VSFs measured for all eight nebulae are best explained by subsonic turbulence revealed by the line-emitting gas, which in turn strongly suggests that the cool gas ( T ∼ 10 ^4 K) is dynamically coupled to the hot ambient medium. Previous work demonstrates that the largest nebulae in our sample reside in group environments with clear signs of tidal interactions, suggesting that environmental effects are vital in seeding and enhancing the turbulence within the gaseous halos, ultimately promoting the formation of the extended nebulae. No discernible differences are observed in the VSF properties between radio-loud and radio-quiet QSO fields. We estimate the turbulent heating rate per unit volume, Q _turb , in the QSO nebulae to be ∼10 ^−26 –10 ^−22 erg cm ^−3 s ^−1 for the cool phase and ∼10 ^−28 –10 ^−25 erg cm ^−3 s ^−1 for the hot phase. This range aligns with measurements in the intracluster medium and star-forming molecular clouds but is ∼10 ^3 times higher than the Q _turb observed inside cool gas clumps on scales ≲1 kpc using absorption-line techniques. We discuss the prospect of bridging the gap between emission and absorption studies by pushing the emission-based VSF measurements to below ≈10 kpc.

We present a detailed study of cool, neutral gas traced by Lya around 4595 z<0.5 galaxies using stacks of background quasar spectra. The galaxies are selected from our MUSEQuBES low-z survey along with data from the literature. These galaxies, with a median stellar mass of log (M*/Msun)= 10.0, are probed by 184 background quasars giving rise to 5054 quasar-galaxy pairs. The median impact parameter is b = 1.5 pMpc (median b/Rvir=10.4) with 204 (419) quasar-galaxy pairs probing b/Rvir < 1 (2). We find excess absorption out to at least ~ 15 Rvir transverse distance and ~ 600 km/s along the line of sight. We show that the median stacked profile for the full sample, dominated by the pairs with b > Rvir, can be explained by a galaxy-absorber two-point correlation function with r0 = 7.6 pMpc and gamma = -1.57. There are strong indications that the inner regions (< Rvir) of the rest equivalent width profile are better explained by a log-linear (or a Gaussian) relation whereas the outer regions are well described by a power-law, consistent with galaxy-absorber large-scale clustering. Using a sub-sample of 339 galaxies (442 quasar-galaxy pairs, median b/Rvir = 1.6) with star formation rate measurements, we find that the Lya absorption is significantly stronger for star-forming galaxies compared to passive galaxies, but only within the virial radius. The Lya absorption at b ~ Rvir for a redshift-controlled sample peaks at M* ~ 10^9 Msun~ (Mhalo ~ 10^11 Msun).

This paper presents a detailed study of the physical properties of seven C IV absorbers identified at z_abs = 0.68-1.28 along the line of sight toward QSO PG 1522+101 (z_QSO = 1.330). The study leverages high-quality QSO spectra from HST COS and STIS, and Keck HIRES to resolve component structures and to constrain the gas density and elemental abundances of individual components. Under the assumption of photoionization equilibrium (PIE), five of the 12 C IV components require a mixture of high- and low-density phases to fully explain the observed relative abundances between low-, intermediate-, and high-ionization species. In addition, galaxy surveys carried out using VLT MUSE and Magellan LDSS3c are utilized to characterize the galaxy environments. The results of this analysis are summarized as follows: (1) no luminous galaxies (> 0.1 L*) are found within 100 kpc in projected distance from the C IV absorbers; (2) the C IV selection preferentially targets high-metallicity (near solar) and chemically-evolved gas ( solar [C/O] elemental abundances) in galaxy halos; (3) the observed narrow line widths of individual C IV components, places a stringent limit on the gas temperature (< 5e4 K) and supports a photoionization origin; (4) additional local ionizing sources beyond the UV ionizing background may be necessary for at least one absorber based on the observed deficit of He I relative to H I; and (5) a PIE assumption may not apply when the gas metallicity exceeds the solar value and the component line width implies a warmer temperature than expected from PIE models.

ABSTRACT We present the first comprehensive study of a giant, ≈70 kpc-scale nebula around a radio-quiet quasar at z < 1. The analysis is based on deep integral field spectroscopy with Multi-Unit Spectroscopic Explorer of the field of HE 0238−1904, a luminous quasar at z = 0.6282. The nebula emits strongly in [O ii], $\rm H \beta$, and [O iii], and the quasar resides in an unusually overdense environment for a radio-quiet system. The environment likely consists of two groups which may be merging, and in total have an estimated dynamical mass of Mdyn ≈ 4 × 1013 to 1014 M⊙. The nebula exhibits largely quiescent kinematics and irregular morphology. The nebula may arise primarily through interaction-related stripping of circumgalactic and interstellar medium (CGM/ISM) of group members, with some potential contributions from quasar outflows. The simultaneous presence of the giant nebula and a radio-quiet quasar in a rich environment suggests a correlation between such circum-quasar nebulae and environmental effects. This possibility can be tested with larger samples. The upper limits on the electron number density implied by the [O ii] doublet ratio range from $\log (n_{\rm e, [O\,{\small II}]} /\mathrm{cm}^{-3})<1.2$ to 2.8. However, assuming a constant quasar luminosity and negligible projection effects, the densities implied from the measured line ratios between different ions (e.g. [O ii], [O iii], and [Ne v]) and photoionization simulations are often 10−400 times larger. This large discrepancy can be explained by quasar variability on a time-scale of ≈104−105 yr.

ABSTRACT Much of what is known of the chemical composition of the universe is based on emission line spectra from star-forming galaxies. Emission-based inferences are, nevertheless, model-dependent and they are dominated by light from luminous star-forming regions. An alternative and sensitive probe of the metallicity of galaxies is through absorption lines imprinted on the luminous afterglow spectra of long gamma ray bursts (GRBs) from neutral material within their host galaxy. We present results from a JWST/NIRSpec programme to investigate for the first time the relation between the metallicity of neutral gas probed in absorption by GRB afterglows and the metallicity of the star-forming regions for the same host galaxy sample. Using an initial sample of eight GRB host galaxies at z = 2.1–4.7, we find a tight relation between absorption and emission line metallicities when using the recently proposed $\hat{R}$ metallicity diagnostic (±0.2 dex). This agreement implies a relatively chemically homogeneous multiphase interstellar medium and indicates that absorption and emission line probes can be directly compared. However, the relation is less clear when using other diagnostics, such as R23 and R3. We also find possible evidence of an elevated N/O ratio in the host galaxy of GRB 090323 at z = 4.7, consistent with what has been seen in other z > 4 galaxies. Ultimate confirmation of an enhanced N/O ratio and of the relation between absorption and emission line metallicities will require a more direct determination of the emission line metallicity via the detection of temperature-sensitive auroral lines in our GRB host galaxy sample.

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 present a statistical study of the properties of diffuse HI in ten nearby galaxies, comparing the HI detected by the single-dish telescope FAST (FEASTS program) and the interferometer VLA (THINGS program), respectively. The THINGS' observation missed HI with a median of 23% due to the short-spacing problem of interferometry and limited sensitivity. We extract the diffuse HI by subtracting the dense HI, which is obtained from the THINGS data with a uniform flux-density threshold, from the total HI detected by FAST. Among the sample, the median diffuse-HI fraction is 34%, and more diffuse HI is found in galaxies exhibiting more prominent tidal-interaction signatures. The diffuse HI we detected seems to be distributed in disk-like layers within a typical thickness of $1\,\text{kpc}$, different from the more halo-like diffuse HI detected around NGC 4631 in a previous study. Most of the diffuse HI is cospatial with the dense HI and has a typical column density of $10^{17.7}$-$10^{20.1}\,\text{cm}^{-2}$. The diffuse and dense HI exhibits a similar rotational motion, but the former lags by a median of 25% in at least the inner disks, and its velocity dispersions are typically twice as high. Based on a simplified estimation of circum-galactic medium properties and assuming pressure equilibrium, the volume density of diffuse HI appears to be constant within each individual galaxy, implying its role as a cooling interface. Comparing with existing models, these results are consistent with a possible link between tidal interactions, the formation of diffuse HI, and gas accretion.

ABSTRACT Gaseous, disc–halo interfaces are shaped by processes that are critical to galaxy evolution, including gas accretion and outflows. Extraplanar diffuse ionized gas (eDIG) layers are characterized by scale heights that largely exceed those predicted by their temperature, suggesting the presence of turbulent energy injection from star-formation feedback. However, the origin of this large-scale height remains uncertain. To explore the connection between eDIG and star-forming discs, we present a spatially resolved case study of a nearby pair of sub-$L_*$, intermediately inclined disc galaxies NGC 3511/3513. We decompose optical nebular lines observed using long-slit spectroscopy into narrow and broad velocity components. In NGC 3511, the broad component has three distinctive characteristics in comparison to the narrow component: (1) significantly higher velocity dispersions (a median $\langle \sigma \rangle _{\text{Broad}} = 24$ km s$^{-1}$compared to $\langle \sigma \rangle _{\text{Narrow}} = 13$ km s$^{-1}$), (2) elevated [N ii]$\lambda$6583/H$\alpha$ and [S ii]$\lambda$6716/H$\alpha$ line ratios, and (3) a rotational velocity lag. These characteristics support the origin of the broad component in an extraplanar, gaseous disc. In NGC 3513, the broad component reveals disc–halo circulation via localized outflows at radius $\lesssim 1$ kpc. For NGC 3511, we test a vertical hydrostatic equilibrium model with pressure support supplied by thermal and turbulent motions. Under this assumption, the eDIG velocity dispersion corresponds to a scale height $h_{z} \gtrsim 0.2 - 0.4$ kpc at $R = 3 - 5$ kpc, a factor of a few above the thermal scale height ($h_{z} \lesssim 0.1$ kpc). This highlights the importance of turbulent motions to the vertical structure of the gaseous, disc–halo interface.