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| circumgalactic medium | |
|---|---|
| Name | Circumgalactic medium |
| Type | Gaseous halo |
circumgalactic medium
The circumgalactic medium is the diffuse, multiphase gaseous envelope surrounding galaxies that mediates exchanges between galaxies and the larger-scale universe. It links processes in galactic disks and halos to environments traced by galaxy clusters, filaments of the Cosmic web, and reservoirs associated with Intergalactic medium structures. Studies connect observations from facilities like the Hubble Space Telescope, Chandra X-ray Observatory, and Atacama Large Millimeter/submillimeter Array to theoretical frameworks developed by groups at institutions such as the Max Planck Institute for Astronomy, Harvard–Smithsonian Center for Astrophysics, and Princeton University.
The circumgalactic medium occupies scales from the optical extent of a galaxy to its virial radius as defined in models by researchers at California Institute of Technology and University of Cambridge. Early recognition arose from absorption-line studies associated with objects cataloged by teams at the Sloan Digital Sky Survey and from X-ray halos characterized in work at the European Space Agency. Definitions intersect with concepts used in papers from the National Aeronautics and Space Administration and conference proceedings of the International Astronomical Union.
The medium contains ionized gas, neutral atomic clouds, molecular clumps, dust, magnetic fields, and cosmic rays, with phases analogous to multiphase descriptions used in analyses at the Lawrence Berkeley National Laboratory and Max Planck Institute for Astrophysics. Temperatures span from ~10^2 K in cold clumps referenced by teams at University of California, Santa Cruz to >10^6 K hot plasma studied by researchers at Stanford University and the European Southern Observatory. Metallicity gradients derive from enrichment by supernovae associated with stellar populations investigated by groups at University of Oxford and Columbia University. Pressure balance and turbulence measurements employ techniques refined at the Space Telescope Science Institute and the Kavli Institute for Cosmology. Mass estimates relate to halo mass functions developed in work at University of Chicago and Yale University.
Key observational probes include ultraviolet absorption lines, X-ray emission, radio 21-cm absorption, and millimeter molecular tracers used by consortia such as the ALMA Partnership and teams on the Hubble COS (Cosmic Origins Spectrograph) surveys. Absorption-line measurements against background quasars from programs linked to Keck Observatory and Very Large Telescope have revealed ions like O VI and Mg II in studies led by researchers at University of Arizona and Rutgers University. X-ray detections of hot halos derive from observational campaigns using XMM-Newton and Chandra X-ray Observatory, with analyses produced by groups at NASA Goddard Space Flight Center and Columbia University. Radio observations assessing neutral hydrogen invoke facilities such as the Very Large Array and Parkes Observatory where survey teams from CSIRO and National Radio Astronomy Observatory contributed.
The circumgalactic medium regulates gas accretion, star formation, and feedback cycles invoked in models developed at Princeton University and University of California, Berkeley. Outflows driven by supernovae and active galactic nuclei studied in work at Massachusetts Institute of Technology and University of Cambridge pollute the medium with metals, shaping the baryon cycle discussed in symposia at the Royal Astronomical Society. Observational correlations between galaxy stellar mass and CGM properties appear in datasets from the Sloan Digital Sky Survey and surveys coordinated by the European Space Agency.
Interfaces between the circumgalactic medium and the intergalactic medium manifest at locations cataloged in large-scale maps from the Two-degree Field Galaxy Redshift Survey and the Baryon Oscillation Spectroscopic Survey. Environmental effects including ram pressure stripping near clusters such as those studied in the Perseus Cluster and Coma Cluster alter CGM structure, as examined by teams at the Max Planck Institute for Extraterrestrial Physics and CfA. Galaxy mergers exemplified by systems investigated at Hubble Space Telescope lead to transient CGM disturbances analyzed by researchers at University of Toronto and Carnegie Institution for Science.
State-of-the-art cosmological simulations like those from the IllustrisTNG project and the EAGLE collaboration incorporate CGM physics developed at institutions including Max Planck Institute for Astrophysics and University of Durham. High-resolution zoom simulations from groups at Flatiron Institute and Yale University probe turbulence, cooling, and conduction, while subgrid models of feedback have been informed by work at Massachusetts Institute of Technology and Harvard University. Analytical treatments build on frameworks proposed by researchers at Princeton University and Cambridge University Press-affiliated authors.
Outstanding issues include the baryon budget reconciliation pursued by teams at NASA, the lifecycle of cold streams highlighted by researchers at University of California, Santa Barbara, and the microphysics of mixing studied using methods from laboratories collaborating with Stanford University. Upcoming facilities such as the James Webb Space Telescope, Square Kilometre Array, and next-generation X-ray missions backed by agencies like European Space Agency and NASA will enable progress pursued by consortia at California Institute of Technology and University of Cambridge. Multiwavelength campaigns coordinated by observatories including Keck Observatory and Atacama Large Millimeter/submillimeter Array will refine models from the IllustrisTNG and EAGLE projects and address questions raised in meetings of the American Astronomical Society.
Category:Galactic astronomy