Modeling Lyα emission from high-z galaxies Stockholm get-together, 2010 Dark Cosmology Centre | Niels Bohr Institutet | Københavns Universitet www.dark-cosmology.dk/~pela

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)

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

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

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

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

Effects of dust Central parts affected most ⇒ Spectrum is narrowed

Effects of dust Dust/nodust-ratio resembles a Gaussian

Escape fraction

IGM transmission

IGM transmission

Homogeneous universe

Retarded Hubble flow

Retarded Hubble flow

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

Impact on the Lya profile

Summary • Dust makes SB profile more extended

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

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

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