Search for: All records

Abstract How do galaxies of different luminosities contribute to the metal absorber populations of varying species and strength? We present our analysis of the predicted metal contributions from galaxies as observed in quasar absorption line spectra during the end of the epoch of reionization (10 ≥z≥ 5.5). This was done by implementing on-the-fly particle tracking into the latestTechnicolor Dawnsimulation and then linking Cii, Civ, Siii, Siiv, Oi, and Mgiiabsorbers to host galaxies in postprocessing. We define the host galaxy luminosity distribution (HGLD) as the rest-frame ultraviolet luminosity distribution of galaxies contributing ions to an absorber, weighted by the fractional contribution, and compute its dependence on ion and absorber strength. The HGLD shape is predicted to be indistinguishable from the field luminosity function, indicating that there is no relationship between the absorber strength or ion and the luminosity of the dominant contributing galaxy. Switching from galaxy luminosity to stellar mass, the predicted host galaxy mass distributions (HGMDs) indicate that more-massive galaxies contribute a higher fraction of metal ions to absorbers of each species, with the HGMDs of stronger absorbers extending out to higher masses. We conclude that the fraction of absorbing metal ions contributed by galaxies increases weakly with stellar mass, but the scatter in luminosity at fixed stellar mass obscures this relationship. For the same reason, we predict that observational analyses of the absorber–galaxy relationship will uncover stronger trends with stellar mass than with luminosity. 

Abstract We explore how the assumption of ionization equilibrium modulates the modeled intergalactic medium at the end of the hydrogen epoch of reionization using the cosmological radiation hydrodynamicTechnicolor Dawnsimulation. In neutral and partially ionized regions where the metagalactic ultraviolet background is weak, the ionization timescalet_ion≡ Γ⁻¹exceeds the Hubble time. Assuming photoionization equilibrium in such regions artificially boosts the ionization rate, accelerating reionization. By contrast, the recombination timet_rec<t_ionin photoionized regions, with the result that assuming photoionization equilibrium artificially increases the neutral hydrogen fraction. Using snapshots in the range 8 ≥z≥ 5, we compare the predicted Lyαforest (LAF) flux power spectrum with and without the assumption of ionization equilibrium. Small scales (k> 0.1 rad s km⁻¹) exhibit reduced power from 7 ≤z≤ 5.5 in the ionization equilibrium case, while larger scales are unaffected. This occurs for the same reasons: ionization equilibrium artificially suppresses the neutral fraction in self-shielded gas and boosts ionizations in voids, suppressing small-scale fluctuations in the ionization field. When the volume-averaged neutral fraction drops below 10⁻⁴, the signature of nonequilibrium ionizations on the LAF disappears. Comparing with recent observations indicates that these nonequilibrium effects are not yet observable in the LAF flux power spectrum.