Galactic Winds and Extended Lya Emission from the Host Galaxies of High Column Density QSO Absorption Systems

摘要

We present 3D resonant radiative transfer simulations of the spatial andspectral diffusion of the Lya radiation from a central source in the hostgalaxies of high column density absorption systems at z ~ 3. The radiativetransfer simulations are based on a suite of cosmological galaxy formationsimulations that reproduce a wide range of observed properties of damped Lyaabsorption systems. The Lya emission is predicted to be spatially extended upto several arcsec, and the spectral width of the Lya emission is broadened toseveral hundred (in some case more than thousand) km/s. The distribution andthe dynamical state of the gas in the simulated galaxies is complex, the latterwith significant contributions from rotation and both in- and out-flows. Theemerging Lya radiation extends to gas with column densities of N_HI ~ 10^{18}cm^{-2} and its spectral shape varies strongly with viewing angle. The strongdependence on the central \hi column density and the HI velocity field suggeststhat the Lya emission will also vary strongly with time on timescales of a fewdynamical times of the central region. Such variations with time should beespecially pronounced at times where the host galaxy undergoes a major mergerand/or starburst. Depending on the pre-dominance of in- or out-flow along agiven sightline and the central column density, the spectra show prominent bluepeaks, red peaks or double-peaked profiles. Both spatial distribution andspectral shape are very sensitive to details of the galactic windimplementation. Stronger galactic winds result in more spatially extended Lyaemission and - somewhat counterintuitively - a narrower spectral distribution.