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Probing the Galaxy with Superbubbles 3D Simulations

Probing the Galaxy with Superbubbles 3D Simulations. Nicole Wityk University of Calgary. Outline. Analytic Models Our Simulations Setup Hydrodynamic Simulations Magnetohydrodynamic Simulations Bubbles as Probes Axial ratios Fitting Kompaneets to Magnetized bubbles Faraday Rotation.

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Probing the Galaxy with Superbubbles 3D Simulations

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  1. Probing the Galaxy with Superbubbles3D Simulations Nicole Wityk University of Calgary

  2. Outline • Analytic Models • Our Simulations • Setup • Hydrodynamic Simulations • Magnetohydrodynamic Simulations • Bubbles as Probes • Axial ratios • Fitting Kompaneets to Magnetized bubbles • Faraday Rotation Probing the Galaxy with Superbubbles 3D Simulations

  3. Analytic Model: Castor • Analytic solution • Assumption: Constant Atmosphere • Spherical evolution • Solves for the radius as a function of time Probing the Galaxy with Superbubbles 3D Simulations

  4. Analytic ModelKompaneets • Analytic Solution • Assumption Exponential Atmosphere • Evolution • Early Stages • Radius << Scale Height • Spherical • Late Stages • Radius > Scale Height • Elongated Probing the Galaxy with Superbubbles 3D Simulations

  5. Our Simulations • Fully 3D Numerical Simulations • ZEUSMP MHD code (Heyes et al. 2006) • Adiabatic evolution in an initially isothermal atmosphere • HD and MHD simulations • Determine the effects of magnetic fields on bubble morphology • Effect of fitting analytic hydrodynamic solutions to magnetized bubbles on values derived from those fits Probing the Galaxy with Superbubbles 3D Simulations

  6. Our SimulationsSetup • Two ISM density distributions in isothermal medium: • Exponential • Dickey & Lockman (1990) • Two magnetic field geometries: • B = constant • B ~ r1/2 (equipartition) • Magnetic field strength • b = Pgas / Pmag • Resolution: 200 x 200 x 200 (5 pc pixels) Probing the Galaxy with Superbubbles 3D Simulations

  7. z z x y SimulationHydrodynamic • Mechanical Luminosity: LM,Source = 3 x 1037 erg/s • Atmosphere: Exponential • Magnetic Field: None Probing the Galaxy with Superbubbles 3D Simulations

  8. SimulationHydrodynamic • LM,source = 3 x 1037 erg/s • Atmosphere: Exponential Log d Z Y X X Probing the Galaxy with Superbubbles 3D Simulations

  9. SimulationHydrodynamic • LM,source = 3 x 1037 erg/s • Atmosphere: Dickey & Lockman Probing the Galaxy with Superbubbles 3D Simulations

  10. z z y x SimulationMagnetohydrodynamic • Mechanical Luminosity: LM,Source = 3 x 1037 erg/s • Atmosphere: Exponential • Magnetic Field: Constant B, b = 1 Probing the Galaxy with Superbubbles 3D Simulations

  11. SimulationMagnetohydrodynamic • L M,source= 3 x 1037 erg/s • Atmosphere: Exponential • Constant B, b = 1 Log d Z Y X X Probing the Galaxy with Superbubbles 3D Simulations

  12. Bubbles as Probes • Axial Ratios • Fitting Kompaneets Solution with continuous injection (Basu et al. 1999) to Magnetized Bubbles • Faraday Rotation Probing the Galaxy with Superbubbles 3D Simulations

  13. Exp, B a r1/2 Exp, Constant B Axial ratio (Y/X) DL, B a r1/2 DL, Constant B Axial RatiosY/X Y/X Axial ratios at level of source Y Y X X Probing the Galaxy with Superbubbles 3D Simulations

  14. Fitting Kompaneets to Magnetized Bubbles • W4 Chimney • Located in Perseus arm • 2.35 kpc away • Source: OCl 352 (l,b = 134˚.7,0.˚9) • 110 pc across at b = 3˚.5 110 pc Probing the Galaxy with Superbubbles 3D Simulations

  15. Fitting Kompaneets to Magnetized Bubbles Possible Problems W4 may be a magnetized bubble Kompaneets solution does not take magnetic fields into account Question What effect does fitting a hydrodynamic model to a magnetized bubble have on derived values? Basu et al 1999 Fitted Kompaneets Solution to W4 Chimney • Age: 2.5 Myr • Scaleheight: 25pc 110 pc Probing the Galaxy with Superbubbles 3D Simulations

  16. Fitting Kompaneets toMagnetized Bubbles MAIN RESULT • Overlays fit to magnetic bubbles give lower values for scaleheight by 30-50% and for age by 50% Simulation Data • b = 1, H = 100 pc • Age = 7.3 Myr Green Overlay • H = 60 pc • Age = 2.79 Myr White Overlay • H = 110 pc • Age = 3.78 Myr YZ Plane Analytic Kompaneets Solution Source Location Probing the Galaxy with Superbubbles 3D Simulations

  17. Effect of Magnetic Field MHD Simulation • Green arrows: direction and strength of B field projected onto the plane • Magnetic field wraps around the cavity XZ plane Probing the Galaxy with Superbubbles 3D Simulations

  18. Faraday RotationSmall scale structure Dickey & Lockman Atmosphere, B = const, b = 1, t = 10 Myr X-Y X-Z Y-Z X-Y Y-Z X-Z Probing the Galaxy with Superbubbles 3D Simulations

  19. Summary • Bubbles evolve differently depending on magnetic fields present • Axial ratio in the plane of the Galaxy is independent of magnetic configuration and atmosphere • Fitting Kompaneets to a magnetized bubble with line of sight along field lines results in smaller scale height • Rotation Measure maps can reveal the magnetic or density structure of the medium surrounding a superbubble Work in Progress • Effect of cooling on morphology of magnetized and non magnetized bubbles Probing the Galaxy with Superbubbles 3D Simulations

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