Single-phase photoionization equilibrium (PIE) models are often used to infer the underlying physical properties of galaxy halos probed in absorption with ions at different ionization potentials. To incorporate the effects of turbulence, we use the MAIHEM code to model an isotropic turbulent medium exposed to a redshift zero metagalactic UV background, while tracking the ionizations, recombinations, and species-by-species radiative cooling for a wide range of ions. By comparing observations and simulations over a wide range of turbulent velocities, densities, and metallicity with a Markov chain Monte Carlo technique, we find that MAIHEM models provide an equally good fit to the observed low-ionization species compared to PIE models, while reproducing at the same time high-ionization species such as \ion{Si}{4} and \ion{O}{6}. By including multiple phases, MAIHEM models favor a higher metallicity ($Z/Z_\odot \approx 40\%$) for the circumgalactic medium compared to PIE models. Furthermore, all of the solutions require some amount of turbulence ($σ_{\rm 3D} \geqslant 26\ {\rm km}\ {\rm s}^{-1}$). Correlations between turbulence, metallicity, column density, and impact parameter are discussed alongside mechanisms that drive turbulence within the halo.
The circumgalactic medium (CGM) of nearby star-forming galaxies shows clear indications of OVI absorption accompanied by little to no detectable NV absorption. This unusual spectral signature, accompanied by highly non-uniform absorption from lower ionization state species, indicates that the CGM must be viewed as a dynamic, multiphase medium, such as occurs in the presence of turbulence. Motivated by previous isotropic turbulent simulations, we carry out chemodynamical simulations of stratified media in a Navarro-Frenk-White (NFW) gravitational potential with a total mass of $10^{12}$ solar m…
The circumgalactic medium (CGM) of nearby star-forming galaxies show clear indications of \ion{O}{6} absorption accompanied by little to no \ion{N}{5} absorption. This unusual spectral signature, accompanied by absorption from lower ionization state species whose columns vary by orders of magnitude along \st{difference} \textbf{different} sightlines, indicates that the CGM must be viewed as a dynamic, multiphase medium, such as occurs in the presence of turbulence. To explore this possibility, we carry out a series of chemodynamical simulations of a isotropic turbulent media, using the MAIHEM …
In Churchill et al., we used halo abundance matching applied to 182 galaxies in the MgII Absorber-Galaxy Catalog (MAGIICAT, Nielsen et al.) and showed that the mean MgII 2796 equivalent width follows a tight inverse-square power law, W_r(2796) ~ (D/R_vir)^-2, with projected location relative to the galaxy virial radius and that the MgII absorption covering fraction is invariant with galaxy virial mass, M_h, over the range 10.7 < M_h/M_solar < 13.9. In this work, we explore multivariate relationships between W_r(2796), virial mass, impact parameter, virial radius, and the theoretical cooling ra…
Absorption-line measurements of the circumgalactic medium (CGM) display a highly non-uniform distribution of lower ionization state species accompanied by more widespread higher ionization state material. This suggests that the CGM is a dynamic, multiphase medium, such as arises in the presence of turbulence. To better understand this evolution, we perform hydrodynamic and magneto-hydrodynamic (MHD) simulations of the CGM surrounding Milky Way-like galaxies. In both cases, the CGM is initially in hydrostatic balance in a $10^{12}$ solar masses dark matter gravitational potential, and the simul…
In massive objects, such as galaxy clusters, the turbulent velocity dispersion, $σ_\mathrm{turb}$, is tightly correlated to both the object mass, $M$, and the thermal energy. Here, we investigate whether these scaling laws extend to lower-mass objects in dark-matter filaments. We perform a cosmological zoom-in simulation of a filament using an adaptive filtering technique for the resolved velocity component and a subgrid-scale model to account for the unresolved component. We then compute the mean turbulent and thermal energies for all halos in the zoom-in region and compare different definiti…
In major galaxy mergers, the orbits of stars are violently perturbed, and gas is torqued to the centre, diluting the gas metallicity and igniting a starburst. In this paper, we study the gas dynamics in and around merging galaxies using a series of cosmological magneto-hydrodynamical (MHD) zoom-in simulations. We find that the gas bridge connecting the merging galaxies pre-coalescence is dominated by turbulent pressure, with turbulent Mach numbers peaking at values of 1.6-3.3. This implies that bridges are dominated by supersonic turbulence, and are thus ideal candidates for studying the impac…
Kinematics of H I and O VI Absorbers: Insights into the Turbulence Driver of the Multiphase Circumgalactic Medium
Tsinghua University（清华大学）；The University of Chicago（芝加哥大学）；Peking University（北京大学）；Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut（海德堡大学天文中心，天文计算研究所）
We provide an analytic framework for interpreting observations of multiphase circumgalactic gas that is heavily informed by recent numerical simulations of thermal instability and precipitation in cool-core galaxy clusters. We start by considering the local conditions required for the formation of multiphase gas via two different modes: (1) uplift of ambient gas by galactic outflows, and (2) condensation in a stratified stationary medium in which thermal balance is explicitly maintained. Analytic exploration of these two modes provides insights into the relationships between the local ratio of…
The circumgalactic medium (CGM) is closely linked to galaxy formation and evolution, but difficult to characterize observationally and typically poorly resolved in cosmological simulations. We use spherically-symmetric, idealized, high-resolution simulations of the CGM in $10^{12}M_\odot$ and $10^{11}M_\odot$ dark matter halos to characterize the gas pressure, turbulent and radial velocities, and degree of thermal and effective dynamic pressure support in the overall CGM as well as in its high- and low-temperature phases. We find that the $10^{12}M_\odot$ halo contains a CGM mostly formed of a…
The circumgalactic medium (CGM) is one of the frontiers of galaxy formation and intimately connected to the galaxy via accretion of gas on to the galaxy and gaseous outflows from the galaxy. Here we analyse the magnetic field in the CGM of the Milky Way-like galaxies simulated as part of the \textsc{Auriga} project that constitutes a set of high resolution cosmological magnetohydrodynamical zoom simulations. We show that before $z=1$ the CGM becomes magnetised via galactic outflows that transport magnetised gas from the disk into the halo. At this time the magnetisation of the CGM closely foll…
We analyze the mass, temperature, metal enrichment, and OVI abundance of the circumgalactic medium (CGM) around $z\sim 0.2$ galaxies of mass $10^9 M_\odot <M_\bigstar < 10^{11.5} M_\odot$ in the Illustris simulation. Among star-forming galaxies, the mass, temperature, and metallicity of the CGM increase with stellar mass, driving an increase in the OVI column density profile of $\sim 0.5$ dex with each $0.5$ dex increase in stellar mass. Observed OVI column density profiles exhibit a weaker mass dependence than predicted: the simulated OVI abundance profiles are consistent with those observed …
We combine the Santa-Cruz Semi-Analytic Model (SAM) for galaxy formation and evolution with the circumgalactic medium (CGM) model presented in Faerman et al. (2020) to explore the CGM properties of $L^{*}$ galaxies. We use the SAM to generate a sample of galaxies with halo masses similar to the Milky Way (MW) halo, $M_{\rm vir} \approx 10^{12}~{\rm M_{sun}}$, and find that the CGM mass and mean metallicity in the sample are correlated. We use the CGM masses and metallicities of the SAM galaxies as inputs for the FSM20 model, and vary the amount of non-thermal support. The density profiles in o…
We present gravitational-arc tomography of the cool-warm enriched circumgalactic medium (CGM) of an isolated galaxy (``G1'') at $z \approx 0.77$. Combining VLT/MUSE adaptive-optics and Magellan/MagE echelle spectroscopy we obtain partially-resolved kinematics of MgII in absorption and [OII] in emission. The unique arc configuration allows us to probe 42 spatially independent arc positions transverse to G1, plus 4 positions in front of it. The transverse positions cover G1's minor and major axes at impact parameters of $\approx 10-30$ kpc and $\approx 60$ kpc, respectively. We observe a direct …
Measuring Simulated Circumgalactic Medium Turbulence with Emission-Weighted Projected Velocity Structure Functions in FOGGIE
Northeastern University（东北大学）；University of Nottingham（诺丁汉大学）；California Institute of Technology（加州理工学院）；The Observatories of the Carnegie Institution for Science（卡内基科学研究所天文台）
This paper presents a systematic study of the photoionization and thermodynamic properties of the cool circumgalactic medium (CGM) as traced by rest-frame ultraviolet absorption lines around 26 galaxies at redshift $z\lesssim1$. The study utilizes both high-quality far-ultraviolet and optical spectra of background QSOs and deep galaxy redshift surveys to characterize the gas density, temperature, and pressure of individual absorbing components and to resolve their internal non-thermal motions. The derived gas density spans more than three decades, from $\log (n_{\rm H}/{\rm cm^{-3}}) \approx -…
Cold, non-self-gravitating clumps occur in various astrophysical systems, ranging from the interstellar and circumgalactic medium (CGM), to AGN outflows and solar coronal loops. Cold gas has diverse origins such as turbulent mixing or precipitation from hotter phases. We obtain the analytic solution for a steady pressure-driven 1-D cooling flow around cold, local over-densities, irrespective of their origin. Our solutions describe the slow and steady radiative cooling-driven gas inflow in the saturated regime of nonlinear thermal instability in clouds, sheets and filaments. Such a cooling flow…
Abundant observational evidence indicates that the cooling time t_cool of the hot ambient medium pervading a massive galaxy does not drop much below 10 times the freefall time t_ff at any radius. Theoretical models have accounted for this finding by hypothesizing that cold clouds start to condense out of the ambient medium when t_cool/t_ff < 10 and fuel a strong black-hole feedback response that reheats the ambient gas, but those models have not yet been able to provide a simple explanation for the origin of the critical t_cool/t_ff ratio. This paper explores a heuristic model for condensation…
Spurred by rich, multi-wavelength observations and enabled by new simulations, ranging from cosmological to sub-pc scales, the last decade has seen major theoretical progress in our understanding of the circumgalactic medium. We review key physical processes in the CGM. Our conclusions include: (1) The properties of the CGM depend on a competition between gravity-driven infall and gas cooling. When cooling is slow relative to free fall, the gas is hot (roughly virial temperature) whereas the gas is cold (T~10^4 K) when cooling is rapid. (2) Gas inflows and outflows play crucial roles, as does …
We present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous QSOs at $z\!\approx\!0.5$--1.1. Spatially extended nebulae of $\approx\!50$--100 physical kpc in diameter centered on the QSOs are revealed in [OII]$λλ\,3727,3729$ and/or [OIII]$λ\,5008$ emission lines in integral field spectroscopic observations obtained using MUSE on the VLT. We measure the second- and third-order velocity structure functions (VSFs) over a range of scales, from $\lesssim\!5$ kpc to $\approx\!20$--50 kpc, to quantify the turbulent energy transfe…
The chemodynamical signature of coherent metal-poor inflow and enriched recycled accretion in the cool circumgalactic medium
Swinburne University of Technology（斯威本科技大学）；The University of Oklahoma（俄克拉荷马大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；New Mexico State University（新墨西哥州立大学）
Astrophysical gases are commonly multiphase and highly turbulent. In this work, we investigate the survival and growth of cold gas in such a turbulent, multi-phase medium using three-dimensional hydrodynamical simulations. Similar to previous work simulating coherent flow (winds), we find that cold gas survives if the cooling time of the mixed gas is shorter than the Kelvin-Helmholtz time of the cold gas clump (with some weak additional Mach number dependence). However, there are important differences. Near the survival threshold, the long-term evolution is highly stochastic, and subject to th…
There is an emerging consensus that large amounts of gas do not shock heat in the circumgalactic medium (CGM) of massive galaxies, but instead pierce deep into haloes from the cosmic web via filaments. To better resolve this process numerically, we have developed a novel `shock refinement' scheme within the moving mesh code AREPO that adaptively improves resolution around shocks on-the-fly in galaxy formation simulations. We apply this to a massive $\sim10^{12}$ M$_\odot$ halo at $z=6$ using the successful FABLE model, increasing the mass resolution by a factor of 512. With better refinement t…
A common situation in galactic and intergalactic gas involves cold dense gas in motion relative to hot diffuse gas. Kelvin-Helmholtz instability creates a turbulent mixing layer and populates the intermediate-temperature phase, which often cools rapidly. The energy lost to cooling is balanced by the advection of hot high enthalpy gas into the mixing layer, resulting in growth and acceleration of the cold phase. This process may play a major role in determining the interstellar medium and circumgalactic medium phase structure, and accelerating cold gas in galactic winds and cosmic filaments. Co…
Bulk vs. turbulent motions at the centres of galaxy clusters: AGN-driven turbulence according to TNG-Cluster
Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Fakultät für Physik und Astronomie, Universität Heidelberg（海德堡大学物理与天文学院）；Département de Physique, Université de Montréal（蒙特利尔大学物理系）；Universität Heidelberg, Zentrum für Astronomie, ITA（海德堡大学天文学中心）；Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen（海德堡大学跨学科科学计算中心）
The Prevalence of Turbulence-Regulated Multiphase Galactic Winds in Star-Forming Galaxies
Johns Hopkins University（约翰斯·霍普金斯大学）；Max-Planck Institute for Astrophysics（马克斯·普朗克天体物理学研究所）；Universität Heidelberg（海德堡大学）；Northwestern University（西北大学）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Pittsburgh（匹兹堡大学）
Early onset of the hot circumgalactic medium around Milky Way galaxies
Lund University（隆德大学）；University of Bath（巴斯大学）；University of Sydney（悉尼大学）；University of Surrey（萨里大学）；Sorbonne Université（索邦大学）；University of Oxford（牛津大学）
Turbulence in the intracluster, intragroup, and circumgalactic medium plays a crucial role in the self-regulated feeding and feedback loop of central supermassive black holes. We dissect the three-dimensional turbulent `weather' in a high-resolution Eulerian simulation of active galactic nucleus (AGN) feedback, shown to be consistent with multiple multi-wavelength observables of massive galaxies. We carry out post-processing simulations of Lagrangian tracers to track the evolution of enstrophy, a proxy of turbulence, and its related sinks and sources. This allows us to isolate in depth the phy…
Inferring Interstellar Medium Density, Temperature, and Metallicity from Turbulent H II Regions
University of Chicago（芝加哥大学）；Sub-department of Astrophysics, University of Oxford（牛津大学天体物理亚系）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Cosmic Dawn Center (DAWN)（黎明宇宙中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）
The physical and chemical properties of the circumgalactic medium (CGM) at $z\gtrsim6$ have been studied successfully through the absorption in the spectra of background Quasi-Stellar Objects (QSOs). One of the most crucial questions is to investigate the nature and location of the source galaxies that give rise to these early metal absorbers. Theoretical models suggest that momentum-driven outflows from typical star-forming galaxies can eject metals into the CGM and the intergalactic medium (IGM) at z=5-6. Deep, dedicated surveys have searched for Ly$α$ emission associated with strong CIV abs…
The magnetic fields of the dusty nuclei and molecular outflows of Arp 220
University of South Carolina（南卡罗来纳大学）；Institut de Ciències de l’Espai (ICE-CSIC)（太空科学研究所）；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）；Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas (CSIC)（安达卢西亚天体物理研究所，西班牙高等科研理事会）；School of Sciences, European University Cyprus（塞浦路斯欧洲大学理学院）；Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona（巴塞罗那大学量子物理与天体物理学系）；Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona（巴塞罗那大学宇宙科学研究所）
