1. Modeling Lyα emission from high-z galaxies
Stockholm get-together, 2010
Dark Cosmology Centre | Niels Bohr Institutet | Københavns Universitet

2. Modeling Ly profiles Verhamme et al. (2008)
Various scenarios has been invoked:
The fact that Lyα line profiles are often seen to exhibit a P Cygni-like profile has led to the suggestion that high-velocity outflows of gas are needed to enable escape (Kunth et al. 1998; Östlin et al. 2008; Atek et al. 2008).
However, at high redshifts many galaxies are still accreting matter, which should result in an increased blue peak. Since this is rarely observed, the shape could be caused by other mechanisms, e.g. IGM absorption.
Verhamme et al. (2008)

3. Numerical approach Cosmological N-body + hydro simulation
+ hi-res resimulations of interesting regions
+ ionizing UV RT
+ galactic Ly RT with dust
According to the analytical solution of a homogeneous medium, f_esc should be ~10e-5
+ IGM RT

4. Dust
Each cell:
nHI, T, vbulk, LLya, Zi ⇒ nd

5. Initial position of emitted photons
Photons that are eventually absorbed
Photons that eventually escape

6. Effects of dust
Central parts affected most ⇒ Surface brightness profile looks even more extended

7. Effects of dust
Central parts affected most ⇒ Spectrum is narrowed

8. Effects of dust
Dust/nodust-ratio resembles a Gaussian

9. Escape fraction

10. IGM transmission

11. IGM transmission

12. Homogeneous universe

13. Retarded Hubble flow

14. Retarded Hubble flow

15. Transmission as a function of redshift
z = 3.6
z = 5.7
z = 6.3

16. Impact on the Lya profile

17. Summary •
Dust makes SB profile more extended

18. Summary • Dust makes SB profile more extended •
Escape fraction is much smaller for
photons in the wings of the spectrum

19. Summary • Dust makes SB profile more extended •
Escape fraction is much smaller for
photons in the wings of the spectrum •
Escape fraction decreases with increasing Mvir

20. Summary • Dust makes SB profile more extended •
Escape fraction is much smaller for
photons in the wings of the spectrum •
Escape fraction decreases with increasing Mvir •
Retarded Hubble flow may explain at least some of the asymmetric Ly profiles