1. Lyman α – impact of the intergalactic medium
DARS get-together, Ebeltoft, 2010
Dark Cosmology Centre | Niels Bohr Institutet | Københavns Universitet

2. Lyman a • Put constraints on the epoch of reionization
• Crucial for determing redshifts in the hi-z Universe
• Map the Cosmic Web
• Explore young galaxies and a multitude of
of their properties, e.g
• Kinematics and dynamics
• Star formation rates
• Morphology
• Stellar population
• Outflows
• Gas accretion
• Maybe even more I can’t think of right now...

3. Observed Ly profiles
Tapken et al. (2008)

4. 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)

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

6. IGM transmission

7. IGM transmission

8. Ly forest

9. Gunn-Peterson trough

10. Homogeneous universe

11. Retarded Hubble flow

12. Retarded Hubble flow

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

14. Impact on the Lya profile

15. Probing the Epoch of Reionization

16. Probing the Epoch of Reionization
Songaila (2004)

17. Probing the Epoch of Reionization
WMAP: zre = 11.0 ± 1.4
Thomson scattering optical depth:

18. Probing the Epoch of Reionization

19. Summary •
Retarded Hubble flow may explain at least some of the asymmetric Ly profiles
zre,WMAP and zre,QSO could be reconciled through more realistic treatment of the ionization history •