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DGCE SIG Seminar

Diffuse Gas in Cosmic Ecosystems Science Interest Group

DATE

Jun 22, 2023

TIME

4:00 pm EST

COMMUNITY

DGCE SIG

TYPE

Seminar

The Non-Equilibrium Circumgalactic Medium

Cassi Lochhaas (STScI)

The region of space surrounding galaxies, the circumgalactic medium (CGM), is the site of all gas flows into and out of galaxies and is therefore responsible for regulating or promoting galaxy growth. It has been only in the past couple decades that we have been able to observe this tenuous medium, and even more recently that we have been able to resolve it in cosmological simulations. I will discuss the classical theories for the CGM’s role in galaxy evolution and how new, high-resolution cosmological simulations have shown these theories need serious revision. Using the Figuring Out Gas & Galaxies In Enzo (FOGGIE) simulations that resolve the CGM of Milky Way-like galaxies in exquisite detail, I will describe how dynamic gas motions in the CGM like turbulence, rotation, or bulk radial flows drive the galactic ecosystem out of hydrostatic equilibrium, drive its temperature away from the virial temperature, and disrupt inflowing filaments of gas, ultimately affecting how galaxies accrete new gas to convert into stars. These results suggest that the CGM cannot be well-described using equilibrium assumptions – virial, hydrostatic, pressure, nor ionization equilibrium – on the small scales that quasar absorption observations tend to probe, and imply that perhaps the commonly-assumed balance of gas flows in galaxy evolution models need revision as well.

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An illustration of Sun-like star HD 181327 and its surrounding debris disk. The star is at top right. It is surrounded by a far larger debris disk that forms an incomplete ellpitical path and is cut off at right. There’s a huge cavity between the star and the disk. The debris disk is shown in shades of light gray. Toward the top and left, there are finer, more discrete points in a range of sizes. The disk appears hazier and smokier at the bottom. The star is bright white at center, with a hazy blue region around it. The background of space is black. The label Artist's Concept appears at lower left.