Multiwavelength Probes of Galactic Atmospheres

The circumgalactic medium (CGM) can be viewed as an atmosphere that surrounds a galaxy and sustains star formation within it. Much of what we know about the CGM has come from absorption-line spectroscopy, mainly in the UV band, of gas at temperatures below the galaxy's virial temperature. A comparable amount of hotter gas, closer to the virial temperature, may also be present but has been harder to detect. If it is there, then the properties of the cooler clouds and the hotter ambient medium are likely to be complementary, deeply interwoven, and physically complex. It follows that the physics of cosmic rays, magnetic fields, turbulent mixing layers, conductive interfaces, and shocks may then play a leading role in setting the fate of the multiphase CGM. This conference will examine the evidence for a virial-temperature component along with the observations capable of revealing its properties and its relationship to the cooler components. Probes that complement UV absorption-line observations will be emphasized, including X-ray emission and absorption, UV and optical emission, Sunyaev-Zel'dovich probes, Fast Radio Bursts, and signposts of non-thermal particle acceleration.