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OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Simulating the Fermi Bubble
Charles ShugertAdvisor
Dr. Carl Gardner
April 3, 2015
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Outline
I Background and Motivation
I Our Model
I Our Numerical Scheme
I Results
I Future Work
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
Detection of the Fermi Bubbles
I On June 11, 2008, NASA launched the Fermi Gamma-RayTelescope
I On November 2010, two gamma-ray / x-ray bubbles weredetected in the center of the Milky Way
I These bubbles extend symmetrically ≈ 10 kpc above andbelow the Galactic center, with a width ≈ 8.4 kpc
I These bubbles emit gamma-rays at energies between 1 . Eγ .100 GeV, with x-rays emitted at the edge of the bubbles.
I These bubbles have approximately uniform surface brightness.
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
Astrophysical Jets
I Phenomena in which matter is ejected along the axis ofrotation of a an accretion
I Gigantic astrophysical jets are launched from accretion disksaround the central black holes in active galactic nuclei
I The mechanism that drive these jets remains contraversial
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
I Illustration of radio galaxy inearly Universe
I Material emmited via twosymmetric jets, with twolobes at the ends of the jets
I Detected 25 February, 2013;Satellite: Herschel
I Copyright: ESA/C.Carreau/ATG medialab
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
PicturesAstrophysical JetsGoals
Our Goals
I We believe that the Fermi Bubbles are the result of anastrophysical jet pulse that occured millions of years ago
I We hope to uncoverI How old the Fermi Bubbles areI Gain a better understanding of the mechanisim that powers
the Fermi Bubbles
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Approximation
I The outflow velocity of the Fermi Bubbles O(104 kms )I This ammounts to about a 1.01 γ valueI Special Relativistic Effects can be ignored
I Therefore we can use non-relativistic models to simulate theFermi-Bubbles
I We Model the Fermi-Bubbles through the Euler Gas-DynamicEquations
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Euler Gas-Dynamic Equations
∂ρ
∂t+∇ · (ρu) = 0
ρ∂u
∂t+ ρu · ∇u +∇P = 0
∂E
∂t+∇ · (u(E + P)) = −n2Λ(T )
Energy density & pressure (polytropic gas with γ = 5/3)
E =3
2nkBT +
1
2ρu2
P = nkBT
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Our Numerical Method: the 3rd Order WENO Scheme
I High-Order Finite Difference Upwind Method for nonlinearhyperbolic differential equations
I Solves for solutions to nonlinear hyperbolic conservation lawscontaining sharp discontinuities such as shock waves andcontacts
I We use a 13 X 13 kpc2 grid to model the bubble, with a totalrun time of 6.3 million years
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Fermi Bubble Parameters
Units Bubble Ambient Computational Units
ρ Hcm3
ρ=0.06 ρ=60 ρ̄=10−2
P kgkms2
P=1.38·10−4 P=1.38·10−4 P̄=1.67·10−8u kms u=3·10
4 u=0.0 ū=103
Table : Fermi Bubble Parameters
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Further Projects to be investigated
I Further improve the initial conditions of the simulation
I Simulate a 3-D model of the Fermi Bubble
I Create a movie of the Fermi Bubble
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
Acknowledgements & References
Acknowledgements
I Dr. Carl Gardner
I NASA Space Grant
I Friends and Family
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and Motivation
Our ModelOur Numerical Scheme
ResultsFuture Work
Acknowledgements & References
References1. Fox, A., et al., Probing the Fermi Bubbles in Ultraviolet
Absorption: A Spectroscopic Signature of the Milky Way’sBiconical Nuclear Outflow (2015)
2. Guo, F. & Mathews, W. G., The Fermi Bubbles. I. PossibleEvidence for Recent AGN Jet Activity in the Galaxy (2012)
3. Guo, F. & Mathews, W. G., The Fermi Bubbles. II. ThePotential Roles of Viscosity and Cosmic Ray Diffusion in JetModels (2012)
4. Gardner, C. et al., Numerical Simulations of High MachNumber Astrophysical Jets with Radiative Cooling
Charles Shugert Advisor Dr. Carl Gardner Simulating the Fermi Bubble
OutlineBackground and MotivationPicturesAstrophysical JetsGoals
Our ModelOur Numerical SchemeResultsFuture WorkAcknowledgements & References