Hubble Probes the Invisible Halo of a Galaxy

Illustration: NASA, ESA, A. Feild. Science: NASA, ESA, N. Lehner, T. Tripp, J. Tumlinson

FIRE Simulations

Zachary Hafen

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Northwestern University

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Northwestern's Astronomy Center


A variety of observational and theoretical arguments have made it clear that the circumgalactic medium (CGM) is host to many physical processes critical to galaxy formation. Beyond important open questions concerning the mass, energy and chemical content of the CGM, the community is vigorously debating how the CGM regulates gas accretion onto the galaxy, and how the physical conditions in the CGM are related, for example, to the bi-modality in galaxy colors. We are hence bringing together expert theoreticians and observers to a limited-size workshop at Northwestern University, which will allow thorough discussions of the most pressing open questions related to the CGM.

In order to enable more in-depth discussions of recent developments, observational constraints, and upcoming observational opportunities, the workshop will focus specifically on the low redshift CGM (0 <= z <~1).


(1) To present and discuss physical models for the CGM, with a focus on insights from both analytical and numerical models. Is the CGM of L* and dwarf galaxies a scaled-downed version of the intracluster and intragroup media, or is an alternative description necessary? How do different galaxy feedback processes affect the physical conditions in the CGM? What is the role of thermal instabilities and cool flows in galaxy accretion?

(2) To review available observations of the CGM, and how existing models compare with these observations, including UV and X-ray absorption features, X-ray emission, and other direct and indirect observational constraints on the CGM.

(3) To present and discuss predictions for upcoming observational campaigns (e.g., CGM^2, CASBaH, CUBS, eROSITA), and for future telescopes (e.g., Athena, Lynx, LUVOIR), which can be used to differentiate between different CGM models.
Scientific Organizing Committee

Jonathan Stern, co-chair (CIERA, Northwestern)
Claude-André Faucher-Giguère, co-chair (CIERA, Northwestern)
Hsiao-Wen Chen (University of Chicago)
Jessica K. Werk (University of Washington)

Local Organizing Committee

Gretchen Oehlschlager
Jonathan Stern
Claude-André Faucher-Giguère