Galactic Superwinds: Beyond Phenomenology: March 23 – 29, 2014

Date & Time


Location


March 23 – 29, 2014

Organizers:
Andrew Benson, Carnegie Observatories
Juna Kollmeier, Carnegie Observatories

The goal of this symposium was to bring together leading experts in the theory and observation of galactic superwinds — outflows of mass, momentum and energy from galaxies thought to be driven by radiation and winds from stars, and by supernova explosions. The major topic of discussion was the physics of cold gas flows ejected at high velocity into a low density, hot circumgalactic medium, specifically what physics (magnetic fields, thermal conduction, etc.) must be incorporated to accurately model the evolution of these clouds, and whether these physical processes, with characteristic length scales on the order of 1 parsec, can be resolved in cosmological simulations at any point in the foreseeable future. An alternative to fully resolving cloud physics was suggested. In this approach, a detailed sub-grid model of cloud evolution would be solved for each gas particle in the wind, computing mass, energy and momentum mixing rates with the surroundings. These rates would then be applied to the macroscopic gas distribution in the simulation.

The symposium also addressed the question of how best to compare theory and observation. Quantities that theorists would like to know can be derived from observations only through the addition of many extra assumptions, all adding uncertainty to the measurements. For example, a basic quantity of interest is the mass flux in the wind. Inferring this from observations requires assumptions about the isotropy of the wind, the radius from which it is launched, etc., leading to uncertainties of 1 to 2 orders of magnitude. A major discussion point arising from this issue was, where should theory and observations meet? Should observers attempt to estimate mass fluxes using all of the assumptions described above, or should theorists attempt to model the ionization structure of the outflows in their simulations and extract line profiles from their models that can be compared directly with the observables? Each approach requires assumptions, and it is unclear which approach (or perhaps some middle ground) is optimal. Therefore, attempting both approaches and comparing results would be advisable.

 

Materials:

Publications

 
Publications and preprints resulting from the Simons Symposium on Galactic Superwinds:

  1. The Systematic Properties of the Warm Phase of Starburst-Driven Galactic Winds; T. Heckman, R. Alexandroff, S. Borthakur; in preparation.
  2. Indirect Evidence for Escaping Lyman Continuum Photons in Local Lyman Break Galaxy Analogs; R. Alexandroff, T. Heckman, et al.; submitted to ApJ (2015): http://adsabs.harvard.edu/abs/2015AAS…22525109A.
  3. Connection Between the Circumgalactic Medium and the Atomic Hydrogen Disk in Galaxies; S. Borthakur, T. Heckman, et al.; submitted to ApJ (2015): http://adsabs.harvard.edu/abs/2015AAS…22542701B.
  4. The Launching of Cold Clouds by Galaxy Outflows I: Hydrodynamic Interactions with Radiative Cooling; E. Scannapieco & M. Brüggen; (2015): http://arxiv.org/pdf/1503.06800v1.pdf.
  5. Galaxy Outflows Without Supernovae; S. Sur, E. Scannapieco, E. C. Ostriker; in preparation.
  6. Entrainment in Trouble: Cool Cloud Acceleration and Destruction in Hot Supernova-Driven Galactic Winds; D. Zhang, T. A. Thompson, N. Murray, E. Quataert; to be submitted to MNRAS (2015).
  7. Magnetized gas clouds can survive acceleration by a hot wind; M. McCourt, R. O’Leary, A-M. Madigan, E. Quataert; MNRAS Letters (2015) 449 (1), 2–7: http://dx.doi.org/10.1093/mnras/stv355.
  8. Sub-Eddington Star-Forming Regions Are Super-Eddington: Momentum Driven Outflows from Supersonic Turbulence; A. Thompson & M. R. Krumholz; submitted to MNRAS (2014): http://arxiv.org/abs/1411.1769.
  9. The Lyα Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage; C. L. Martin, M. Dijkstra, A. Henry, K. T. Soto, C. W. Danforth, J. Wong; submitted to ApJ (2015): http://arxiv.org/abs/1501.05946.
  10. Baryon Cycling in the Low-Redshift Circumgalactic Medium: A Comparison of Simulations to the COS-Halos Survey; A. B. Ford, J. K. Werk, R. Davé, J. Tumlinson, R. Bordoloi, N. Katz, J. A. Kollmeier, B. D. Oppenheimer, M. S. Peeples, J. X. Prochaska, D. H. Weinberg; submitted to MNRAS (2015): http://arxiv.org/abs/1503.02084.
  11. The EAGLE project: simulating the evolution and assembly of galaxies and their environments; J. Schaye, R. A. Crain, R. G. Bower, M. Furlong, M. Schaller, T. Theuns, C. D. Vecchia, C. S. Frenk, I. G. McCarthy, J. C. Helly, A. Jenkins, Y. M. Rosas-Guevara, S. D. M. White, M. Baes, C. M. Booth, P. Camps, J. F. Navarro, Y. Qu, A. Rahmati, T. Sawala, P. A. Thomas, J. Trayford; MNRAS (2015) 446 (1), 521–554: http://dx.doi.org/10.1093/mnras/stu2058.
  12. The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations; R. A. Crain, J. Schaye, R. G. Bower, M. Furlong, M. Schaller, T. Theuns, C. D. Vecchia, C. S. Frenk, I. G. McCarthy, J. C. Helly, A. Jenkins, Y. M. Rosas-Guevara, S. D. M. White, J. W. Trayford; submitted to MNRAS (2015): http://arxiv.org/abs/1501.01311.
  13. Evolution of galaxy stellar masses and star formation rates in the EAGLE simulations; M. Furlong, R. G. Bower, T. Theuns, J. Schaye, R. A. Crain, M. Schaller, C. D. Vecchia, C. S. Frenk, I. G. McCarthy, J. Helly, A. Jenkins, Y. M. Rosas-Guevara, submitted to MNRAS (2014): http://arxiv.org/abs/1410.3485.
  14. On the interplay between star formation and feedback in galaxy formation simulations; O. Agertz & A. V. Kravtsov; submitted to and in press at ApJ (2015): http://arxiv.org/abs/1404.2613.
  15. Stellar feedback driven winds and galaxy morphology; O. Agertz & A. Kravtsov; to be submitted.
  16. The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation; Rahmati, J. Schaye, R. G. Bower, R. A. Crain, M. Furlong, M. Schaller, T. Theuns; submitted to MNRAS (2015): http://arxiv.org/abs/1503.05553.
  17. Galaxies that shine: radiation-hydrodynamical simulations of disk galaxies; Rosdahl, J. Schaye, R. Teyssier, O. Agertz; submitted to MNRAS (2015): http://arxiv.org/abs/1501.04632.
  18. Detection of hot, metal-enriched outflowing gas around z ≈ 2.3 star-forming galaxies in the Keck Baryonic Structure Survey; L. Turner, J. Schaye, C. C. Steidel, G. C. Rudie, A. L. Strom; submitted to MNRAS (2014): http://arxiv.org/abs/1410.8214.

Presentation Slides

Rob Crain, Leiden Observatory
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Romeel Davé, Arizona State University
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Nick Gnedin, University of Chicago/Fermilab
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Mark Krumholz, UC Santa Cruz
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Eliot Quataert, UC Berkeley
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Joop Schaye, Leiden Observatory
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David Weinberg, Ohio State
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Session Slides

Richard Bower, University of Durham
Outflow Questions

Rob Crain, Leiden Observatory
Pre-SNe Stellar Winds, Intermediate Age Populations, Momentum Driving Relevance on Scales Beyond GMCs, 1051 erg/SN, Short AGN Duty Cycles, Accuracy of Models (SAM/hydro), Dwarf Galaxy Simulation Parameters v. Observational Constraints

Romeel Davé, Arizona State University
Wind Propagation & Mixing

Nick Gnedin, University of Chicago/Fermilab
How We Should Think About Star Formation

Neal Katz, University of Massachusetts
Phenomenologically Obtained Winds (POW)

Dusan Keres, University of San Diego
Challenges in (Numerical) Galactic Wind Modeling

Mark Krumholz, UC Santa Cruz
Galactic Winds: The “Last pc” Problem

Crystal Martin, UC Santa Barbara
What Is the Mass Flux in Galactic Winds?

Eliot Quataert, UC Berkeley
Galactic Winds (impact of star formation vs. AGNs, role of cosmic rays, level of detail needed/feasible for predictive galaxy formation models)

Brant Robertson, University of Arizona
Physical Coupling of Winds to the Turbulent Interstellar Medium

Evan Scannapieco, Arizona State University
What are the Turbulent Velocity and Scale Height in Starbursting Galaxies?

Joop Schaye, Leiden Observatory
Key Challenges in Wind Modeling

Sijing Shen, UC Santa Cruz
Challenges in Galactic Wind Modeling

Chuck Steidel, Cal Tech
Non-Exhaustive List of Questions

Greg Stinson, Max-Planck-Institut für Astronomie
How Do Outflows Work?

Todd Thompson, Ohio State
Theoretical & Observational Challenges

Freeke van de Voort, UC Berkeley
Aspects in Need of Simulation and Study

David Weinberg, Ohio State
Primary Questions of Galaxy Formation / What Happens to Gas After it is Ejected? / Other Key Isssues

Symposium Agenda

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Galactic Superwinds: Beyond Phenomenology
March 23 – 29, 2014

 
Participants:

Andrew Benson, Carnegie Observatories
Richard Bower, University of Durham
Rob Crain, Leiden Observatory
Romeel Dave, Arizona State University
Nick Gnedin, University of Chicago/Fermilab
Tim Heckman, Johns Hopkins University
Neal Katz, University of Massachusetts
Dusan Keres, University of San Diego
Juna Kollmeier, Carnegie Observatories
Andrey Kravtsov, University of Chicago
Mark Krumholz, UC Santa Cruz
Crystal Martin, UC Santa Barbara
Norman Murray, Canadian Institute of Theoretical Astrophysics
Eliot Quataert, UC Berkeley
Brant Robertson, University of Arizona
Evan Scannapieco, Arizona State University
Joop Schaye, Leiden Observatory
Sijing Shen, UC Santa Cruz
Chuck Steidel, Cal Tech
Greg Stinson, Max-Planck-Institut für Astronomie
Todd Thompson, Ohio State
Freeke van de Voort, UC Berkeley
David Weinberg, Ohio State

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