A numerical code for solving various Lyman alpha (Lya) radiative transfer (RT) problems is presented. The code is suitable for an arbitrary, three-dimensional distribution of Lya emissivity, gas temperature, density, and velocity field. Capable of ha
ndling Lya RT in an adaptively refined grid-based structure, it enables detailed investigation of the effects of clumpiness of the interstellar (or intergalactic) medium. The code is tested against various geometrically and physically idealized configurations for which analytical solutions exist, and subsequently applied to three Lyman-break galaxies, extracted from high-resolution cosmological simulations at redshift z = 3.6. Proper treatment of the Lya scattering reveals a diversity of surface brightness (SB) and line profiles. Specifically, for a given galaxy the maximum observed SB can vary by an order of magnitude, and the total flux by a factor of 3 - 6, depending on the viewing angle. This may provide an explanation for differences in observed properties of high-redshift galaxies, and in particular a possible physical link between Lyman-break galaxies and regular Lya emitters.
To assess the effect of baryonic ``pinching of galaxy cluster dark matter (DM) haloes, cosmological (LCDM) TreeSPH simulations of the formation and evolution of two galaxy clusters have been performed, with and without baryons included. The simulat
ions with baryons invoke star formation, chemical evolution with non-instantaneous recycling, metallicity dependent radiative cooling, strong star-burst, driven galactic super-winds and the effects of a meta-galactic UV field, including simplified radiative transfer. The two clusters have T_X~3 and 6 keV, respectively, and, at z~0, both host a prominent, central cD galaxy. Comparing the simulations without and with baryons, it is found for the latter that the inner DM density profiles, r<50-100 kpc, steepen considerably: Delta(alpha)~0.5-0.6, where -alpha is the logarithmic DM density gradient. This is mainly due to the central stellar cDs becoming very massive, as a consequence of the onset of late time cooling flows and related star formation. Once these spurious cooling flows have been corrected for, and the cluster gravitational potentials dynamically adjusted, much smaller pinching effects are found: Delta(alpha)~0.1. Including the effects of baryonic pinching, central slopes of alpha~1.0 and 1.2 are found for the DM in the two clusters, interestingly close to recent observational findings. For the simulations with baryons, the inner density profile of DM+ICM gas combined is found to be only very marginally steeper than that of the DM, Delta(alpha)<0.05. However, the total matter inner density profiles are found to be Delta(alpha)~0.5 steeper than the inner profiles in the dark matter only simulations.
