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We report the discovery of 11 high-velocity H I clouds at Galactic latitudes of 25°–30°, likely embedded in the Milky Way’s nuclear wind. The clouds are detected with deep Green Bank Telescope 21 cm observations of a 3.2° × 6.2° field around QSO 1H1613-097, located behind the northern Fermi Bubble. Our measurements reach 3sigma limits on NHI as low as 3.1 × 10^17/cm^2, more than twice as sensitive as previous HI studies of the bubbles. The clouds span −180 ≤v_LSR≤ −90 km/s and are the highest-latitude 21 cm high-velocity cloud detected inside the bubbles. Eight clouds are spatially resolved, showing coherent structures with sizes of 4–28 pc, peak column densities of log HI = 17.9–18.7, and HI masses up to 1470M⊙. Several exhibit internal velocity gradients. Their presence at such high latitudes is surprising, given the short expected survival times for clouds expelled from the Galactic center. These objects may be fragments of a larger cloud disrupted by interaction with the surrounding hot gas. 

Abstract This paper investigates the physical conditions of the circumgalactic medium ofL^⋆galaxies through explorations of observed ion tracer gas kinematics and comparisons of observations to different ionization models. For this analysis, we utilize Civobservations from the CIViL^⋆survey (∼0.14 ≤z_gal≤ 0.25) and directly compare them to observations of matched lines of sight from the Cosmic Origins Spectrograph-Halos survey. We find that the kinematic parameters for Civand Oviare likely (>95%) drawn from the same parent distribution, suggesting that these two ions are kinematically coincident andpotentiallyoriginate under the same physical conditions. We find that the measured Civ/Oviand Nv/Oviratios are inconsistent with single-phase equilibrium models. For 70% of the objects in our sample, regions allowed by the column density ratios in the density-temperature space do not overlap, creating a “zone of avoidance.” We also investigate the origins of Civ, Nv, and Oviby exploring a cooling flow model under collisional ionization. We find that both Nvand Oviare consistent with the predictions of the model, but the column densities of Civare ∼2.5 times higher than the predictions. As Civhas a lower ionization energy than Nvand Ovi, it is possible that Civhas contributions from both the warm/hot and cool photoionized phase. 

Abstract We report the small-scale spatial variation in cool (T ∼ 10⁴K) Mgiiabsorption detected in the circumgalactic medium (CGM) of a star-forming galaxy atz ≈ 0.8. The CGM of this galaxy is probed by a spatially extended bright background gravitationally lensed arc atz= 2.76. The background arc continuously samples the CGM of the foreground galaxy at a range of impact parameters between 54 and 66 kpc. The Mgiiabsorption strengths vary by more than a factor of 2 within these ranges. A power-law fit to the fractional variation of absorption strengths yields a coherence length of 5.8 kpc within this range of impact parameters. This suggests a high degree of spatial coherence in the CGM of this galaxy. The host galaxy is driving a strong galactic outflow with a mean outflow velocity ≈ −179 km s⁻¹and mass outflow rate ${\dot{M}}_{\mathrm{out}}\ge 64_{-27}^{+31}$ M_⊙yr⁻¹traced by blueshifted Mgiiand Feiiabsorption lines. The galaxy itself has a spatially extended emission halo with a maximum spatial extent of ≈33 kpc traced by [Oii], [Oiii], and Hβemission lines. The extended emission halo shows kinematic signatures of corotating halo gas with solar metallicity. Taken together, these observations suggest evidence of a baryon cycle that is recycling the outflowing gas to form the next generation of stars. 

ABSTRACT Recent observations from the EIGER JWST program have measured for the first time the quasar–galaxy cross-correlation function at $$z\approx 6$$. The autocorrelation function of faint $$z\approx 6$$ quasars was also recently estimated. These measurements provide key insights into the properties of quasars and galaxies at high redshift and their relation with the host dark matter haloes. In this work, we interpret these data building upon an empirical quasar population model that has been applied successfully to quasar clustering and demographic measurements at $$z\approx 2\!-\!4$$. We use a new, large-volume N-body simulation with more than a trillion particles, FLAMINGO-10k, to model quasars and galaxies simultaneously. We successfully reproduce observations of $$z\approx 6$$ quasars and galaxies (i.e. their clustering properties and luminosity functions), and infer key quantities such as their luminosity–halo mass relation, the mass function of their host haloes, and their duty cycle/occupation fraction. Our key findings are (i) quasars reside on average in $$\approx 10^{12.5}\, {\rm M}_{\odot }$$ haloes (corresponding to $$\approx 5\sigma$$ fluctuations in the initial conditions of the linear density field), but the distribution of host halo masses is quite broad; (ii) the duty cycle of (UV-bright) quasar activity is relatively low ($$\approx 1~{{\ \rm per\ cent}}$$); (iii) galaxies (that are bright in [O iii]) live in much smaller haloes ($$\approx 10^{10.9}\, {\rm M}_{\odot }$$) and have a larger duty cycle (occupation fraction) of $$\approx 13~{{\ \rm per\ cent}}$$. Finally, we focus on the inferred properties of quasars and present a homogeneous analysis of their evolution with redshift. The picture that emerges reveals a strong evolution of the host halo mass and duty cycle of quasars at $$z\approx 2\!-\!6$$, and calls for new investigations of the role of quasar activity across cosmic time. 

Abstract The inner circumgalactic medium (CGM) of galaxies, where disk and halo processes intersect, remains poorly characterized despite its critical role in regulating galaxy evolution. We present results from Project AMIGA Insider, mapping Andromeda’s (M31) inner CGM within 0.25R_vir(∼75 kpc) using 11 QSO sightlines, bringing our total sample to 54 sightlines from the disk to 2R_vir. We detect a clear transition between M31’s thick disk and CGM atR ≲ 30 kpc, where low/intermediate ions show thick-disk corotating components with higher column densities than the CGM ones, while high ions exhibit similar column densities in both the CGM and thick disk. Beyond this region, all ion column densities decrease with impact parameter, with steeper gradients for low ions than high ions. The inner CGM (R ≲ 100 kpc) shows more complex gas phases and multicomponent absorption compared to the predominantly single-component outer CGM. We find no significant azimuthal dependence for any observed ions, suggesting M31’s CGM is shaped by radial processes (e.g., cooling flows, precipitation) rather than disk-aligned outflows. We estimate the total metal mass in M31’s cool (Siii, Siiii, Siiv) CGM withinR_virto be (1.9 ± 0. 3_stat ± 0. 7_sys) × 10⁷M_⊙, leading to a cool gas mass of $\approx 6\times 10^9{(Z/0.3Z_{\odot })}^{-1}$ M_⊙. The warmer Ovigas may contain at least 10 times more metal and gas mass. Compared to the COS-HalosL*galaxies, M31’s cool CGM shows lower Si column densities atR ≲ 0.4R₂₀₀and overall lower cool CGM masses, likely reflecting differences in galaxy mass and environment. 

ABSTRACT We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at z ≈ 1.703 using VLT/MUSE IFU observations. We probe the cool outflowing gas, traced by blueshifted Mg ii and Fe ii absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 – 7 kpc apart within the galaxy, drive the outflows at different velocities (Vout ∼ −161 to −240 km s−1), and mass outflow rates ($$\dot{M}_{out} \sim 183$$ – 527 $${\rm M}_{\odot }\, \mathrm{yr}^{-1}$$). The outflow velocities from different regions of the same galaxy vary by 80 km s−1, which is comparable to the variation seen in a large sample of star-burst galaxies in the local universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5–25 kpc2), we find that outflow velocities vary between ∼ −120 and −242 km s−1, and the mass outflow rates vary between ∼37 and 254 $${\rm M}_{\odot }\, \mathrm{yr}^{-1}$$. The outflow momentum flux in this galaxy is ≥ 100% of the momentum flux provided by star formation in individual regions, and outflow energy flux is ≈ 10% of the total energy flux provided by star formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution. 

Abstract This study addresses how the incidence rate of strong O vi absorbers in a galaxy’s circumgalactic medium (CGM) depends on galaxy mass and, independently, on the amount of star formation in the galaxy. We use Hubble Space Telescope/Cosmic Origins Spectrograph absorption spectroscopy of quasars to measure O vi absorption within 400 projected kpc and 300 km s −1 of 52 galaxies with M * ∼ 3 × 10 10 M ⊙ . The galaxies have redshifts 0.12 < z < 0.6, stellar masses 10 10.1 M ⊙ < M * < 10 10.9 M ⊙ , and spectroscopic classifications as star-forming or passive. We compare the incidence rates of high column density O vi absorption ( N O VI ≥ 10 14.3 cm −2 ) near star-forming and passive galaxies in two narrow ranges of stellar mass and, separately, in a matched range of halo mass. In all three mass ranges, the O vi covering fraction within 150 kpc is higher around star-forming galaxies than around passive galaxies with greater than 3 σ -equivalent statistical significance. On average, the CGM of star-forming galaxies with M * ∼ 3 × 10 10 M ⊙ contains more O vi than the CGM of passive galaxies with the same mass. This difference is evidence for a CGM transformation that happens together with galaxy quenching and is not driven primarily by halo mass. 

Abstract We combine data sets from the CGM 2 and CASBaH surveys to model a transition point, R cross , between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies at z < 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01–20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover H i Ly α . Our best-fitting model is a two-component model that combines a 3D absorber–galaxy cross-correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination of R cross as a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with 10 8 ≤ M ⋆ / M ⊙ ≤ 10 10.5 , we find that R cross ( M ⋆ ) ≈ 2.0 ± 0.6 R vir . Additionally, we find excellent agreement between R cross ( M ⋆ ) and the theoretically determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution at z < 0.5 that distribute T ≈ 10 4 K gas to distances beyond the virial radius. 

Abstract We combine 126 new galaxy-O vi absorber pairs from the CGM 2 survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of O vi absorbers ( N O VI ) on galaxy stellar mass, star-formation rate, and impact parameter. The combined sample consists of 249 galaxy-O vi absorber pairs covering z = 0–0.6, with host galaxy stellar masses M * = 10 7.8 –10 11.2 M ⊙ and galaxy-absorber impact parameters R ⊥ = 0–400 proper kiloparsecs. In this work, we focus on the variation of N O VI with galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the average N O VI within one virial radius of a star-forming galaxy is greatest for star-forming galaxies with M * = 10 9.2 –10 10 M ⊙ . Star-forming galaxies with M * between 10 8 and 10 11.2 M ⊙ can explain most O vi systems with column densities greater than 10 13.5 cm −2 . Sixty percent of the O vi mass associated with a star-forming galaxy is found within one virial radius, and 35% is found between one and two virial radii. In general, we find that some departure from hydrostatic equilibrium in the CGM is necessary to reproduce the observed O vi amount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses.