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The Escape of Lyman-alpha from High-Redshift Galaxies: Factors and Implications

This study investigates the mechanics of Lyman-alpha (Lyα) escape from high-redshift galaxies, considering aspects like gas density, temperature, and dust. We analyze the conditions under which Lyα photons can escape, utilizing analytical models and numerical simulations. The impact of dust on the surface brightness profile and escape fraction is explored, revealing complex dependencies on galactic mass and environment. Our findings suggest that varying factors, including ionized holes and multiphase mediums, significantly influence the Lyα escape process, informing future astronomical observations.

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The Escape of Lyman-alpha from High-Redshift Galaxies: Factors and Implications

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  1. Lyman α — The Great Escape Peter Laursen – Paris, 2009 Dark Cosmology Centre| Niels Bohr Institutet | Københavns Universitet www.dark-cosmology.dk/~pela

  2. Ly escape from high-z galaxies Why? What? How?

  3. Gas density and temperature • Dust density and cross-section Ly escape from high-z galaxies • Analytical attempt (Neufeld 1990)

  4. Multiphase medium? Neufeld (1991); Hansen & Oh (2006) Ly escape from high-z galaxies • – Why does Ly escape after all?

  5. Ly escape from high-z galaxies • – Why does Ly escape after all? • Outflow? Kunth et al. (1999); Verhamme et al. (2006); Östlin et al. (2008)

  6. Ly escape from high-z galaxies • – Why does Ly escape after all? • Ionized holes? Kunth et al. (2003); Hayes et al. (2007)

  7. Ly escape from high-z galaxies • – Why does Ly escape after all? • Ionized cones + • viewing angle? Tenori-Tagle et al. (1999); Mas-Hesse et al. (2003)

  8. Numerical approach • Cosmological N-body + hydro simulation • + LyRT on AMR grid with dust

  9. Dust Four important quantities: • Cross-section:d() • Density:nd • Albedo: A • Phase function:P() AVNH Pei (1991) + Weingartner & Draine (2001) + Gnedin et al. (2008) e.g. Bohlin, Savage & Drake (1978)

  10. Dust Four important quantities: • Cross-section:d() • Density:nd • Albedo: A • Phase function:P()

  11. Dust Four important quantities: • Cross-section:d() • Density:nd • Albedo: A • Phase function:P()

  12. 10-4 ≥ fion ≥ 1 Dust Four important quantities: • Cross-section:d() • Density:nd • Albedo: A • Phase function:P()

  13. Dust Four important quantities: • Cross-section:d() • Density:nd • Albedo: A • Phase function:P() Calzetti et al. (1995); Lillie et al. (1976); Li & Draine (2001) ALy = 0.32 gLy = 0.73

  14. MOCALATA • Emit photon • Propagate thru ISM • Interact with • gas or dust • New and ñ • In each cell: • LLy, T, vbulk, nHI, nHII, ZC,N,O,Mg,Si,S,Ca,Fe • ✞ • New ñ • Scatter/absorb • Escape

  15. Results Surface brightness map: Without scattering

  16. Results Surface brightness map: With scattering and dust; luminous regions affected more

  17. Results  Surface brightness profile: Prominent features smoothed out

  18. Results Surface brightness profile: Dust helps to make profile looks more extended

  19. Results Surface brightness profile: Dust helps to make profile looks more extended Fynbo et al. (2003)

  20. Results Spectrum: Escape fraction smallest in the wings

  21. Results fesc(Mvir): Escape fraction decreases with galactic mass

  22. IGM transmission

  23. IGM transmission z = 3.6 z = 5.7 z = 6.3 Songaila (2004)

  24. IGM transmission z = 3.6 z = 5.7 z = 6.3

  25. Summary • Many factors help facilitating the escape of Ly • Spectrum affected in a highly non-grey fashion • fesc decreases with increasing Mvir • Dust makes SB profile even more extended • Problem can be inversed: Predict results of future observations (e.g. Ultra-VISTA) • You cannot escape the raptor

  26. Summary • Many factors help facilitating the escape of Ly • Spectrum affected in a highly non-grey fashion • fesc decreases with increasing Mvir • Dust makes SB profile even more extended • Problem can be inversed: Predict results of future observations (e.g. Ultra-VISTA) • You cannot escape the raptor

  27. Summary • Many factors help facilitating the escape of Ly • Spectrum affected in a highly non-grey fashion • fesc decreases with increasing Mvir • Dust makes SB profile even more extended • Problem can be inversed: Predict results of future observations (e.g. Ultra-VISTA) • You cannot escape the raptor

  28. Summary • Many factors help facilitating the escape of Ly • Spectrum affected in a highly non-grey fashion • fesc decreases with increasing Mvir • Dust makes SB profile even more extended • Problem can be inversed: Predict results of future observations (e.g. Ultra-VISTA) • You cannot escape the raptor

  29. Summary • Many factors help facilitating the escape of Ly • Spectrum affected in a highly non- grey fashion • fesc decreases with increasing Mvir • Dust makes SB profile even more extended • Problem can be inversed: Predict results of future observations (e.g. Ultra-VISTA) • You cannot escape the raptor

  30. Extra stuff Parameter study: Escape fraction quite insensitive to input parameters (fortunately/unfortunately)

  31. Extra stuff Parameter study: Escape fraction quite insensitive to input parameters (fortunately/unfortunately)

  32. Extra stuff Parameter study: Escape fraction quite insensitive to input parameters (fortunately/unfortunately)

  33. Extra stuff Simulation parameters (in case of obnoxious question):

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