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Radiative Transfer with Sphray (Smoothed Particle Hydrodynamics Ray Tracer)

Radiative Transfer with Sphray (Smoothed Particle Hydrodynamics Ray Tracer). Gabriel Altay Advisor: Rupert Croft Partner in Crime: Inti Pelupessy Carnegie Mellon University. N-body Hydrodynamics Feedback Radiative Transfer. Dark Matter + Adiabatic Ideal Gas + SF, Cooling, SN, BH …

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Radiative Transfer with Sphray (Smoothed Particle Hydrodynamics Ray Tracer)

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  1. Radiative Transfer with Sphray(Smoothed Particle Hydrodynamics Ray Tracer) Gabriel Altay Advisor: Rupert Croft Partner in Crime: Inti Pelupessy Carnegie Mellon University

  2. N-body Hydrodynamics Feedback Radiative Transfer Dark Matter + Adiabatic Ideal Gas + SF, Cooling, SN, BH … Ionization State Cosmological Simulations Detailed Physics vs. Run Time

  3. (The SPH in Sphray)

  4. RT Comparison Project I

  5. Nice Things About Sphray

  6. Speed Ray-cer • SPH particles are stored in an Oct-Tree structure (the number of particles in each leaf is user defined) • For each ray, Sphray uses the Plücker method to perform an Axis Aligned Bounding Box (AABB) Test to determine the particle intersections (Mahovsky and Wyvill, The Journal of Graphics Tools, 2004).

  7. Time Steps • The speed which with ionization fronts travel through gas normally imposes severe time step restraints. • Use of time averaged optical depths and photo ionization rates + iterative solution of ionization fractions allows for much longer time steps. • Method introduced in the code C2-Ray (astro-ph/0508416)

  8. SPH all the way through • No artifacts from interpolating SPH particles onto a grid. • Democratic handling of gravity, hydrodynamics and radiative transfer.

  9. Monte Carlo Sampling • For each ray traced, Sphray samples a spectrum and an emission profile. • Very easy to incorporate sources with arbitrary spectra and arbitrary emission profiles + include background and diffuse ionizing radiation. • Method introduced in the code CRASH (astro-ph/0307117)

  10. Benchmark Testastro-ph/0603199 • 100,000 K Blackbody Spectrum • L = 5.0*1048 ergs/s • n=.001 cm-3 • 100% Hydrogen (by number) • 0% Helium (by number) • Initial Temperature = 100 K • Gas Initially Fully Neutral • Output @ t = 10 Myr, 100Myr, 500Myr years ~ 4 trec

  11. Code Verification: Ionization Fronts(astro-ph/0603199)

  12. Code Verification: Temperature (astro-ph/0603199)

  13. A More Challenging Testastro-ph/0307117 (CRASH) • 60,000 K Blackbody Spectrum • L = 1.0*1038 ergs/s • n=1.0cm-3 • 90% Hydrogen (by number) • 10% Helium (by number) • Initial Temperature = 100 K • Gas Initially Fully Neutral • Output @ t = 600,000 years ~ 5 trec

  14. The following plots are very rough comparisons. They are two plots superimposed, one from the CRASH paper and one from Sphray results. The bottom right corners are aligned. CRASH - Red, Sphray - Green, Cloudy94 - Line

  15. Temperature

  16. Hydrogen I

  17. Hydrogen II

  18. Helium I

  19. Helium II

  20. Helium III

  21. Calculation of ionization bubbles for reionization / 21 cm maps. Escape fraction of galactic photons High resolution feed back models Possible Applications

  22. Thanks!

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