The Lyman-α signature of the first galaxies

We present the Cosmic Lyman-α Transfer code (COLT), a new massively parallel Monte-Carlo radiative transfer code, to simulate Lyman-α (Lyα) resonant scattering through neutral hydrogen (H I) as a probe of the first galaxies. We explore the interaction of centrally pro-duced Lyα radiation with the host galactic environment. The Lyα photons emitted from the luminous starburst region escape with characteristic features in the line profile depending on the density distribution, ionization structure, and bulk velocity fields. For example, the pres-ence of anisotropic ionized bubbles exhibits a tall peak close to line centre with a skewed tail that drops off gradually. Furthermore, moderate ( ∼ 10 km s−1) local outflow is capable of producing an amplified peak redward of line centre when compared with the blue peak. Ideal-ized models of first galaxies explore the effect of mass, anisotropic H II regions, and radiation pressure driven winds on Lyα observables. We employ mesh refinement to resolve critical structures responsible for characteristic Lyα features. We also post-process an ab initio cos-mological simulation and examine images from photons captured at various escape distances within the (1 Mpc)3 comoving volume. Finally, we discuss the emergent spectra and surfac