| Abstract : | We explore the effect of galactic feedback processes and background-radiation-field(UVB) on the detectability, gas phase distribution, and physical conditions of metal species such as CIV, OVI, and NeVIII in low-z IGM. We use three different cosmological hydrodynamical simulations with varied feedback prescriptions at z=0.5. The gas fraction in different density-temperature-phases changes significantly due to variations in feedback, especially the inclusion of AGN feedback increases the metal enrichment in lower overdensities. As most of the absorption comes from a combination of various density-temperature regions, variation UVB introduces two effects, firstly the column density of absorbers changes even if the same number of components are present and secondly, new absorbing components become significant for lower-intensity UVB. Comparing different simulations we find AGN-feedback is necessary to reproduce the observed OVI Column-density-distribution-function(CDDF). For the first time, we show Voigt profile fitted column densities of simulated OVI absorbers produce CDDF in good agreement with the low-z observation. The variation in feedback in simulation with AGN feedback can mimic the effect of UVB variation. Therefore, one needs to compare more observables (like HI-metal association, the association between different ions, and their spatial clustering) with the simulations to draw robust conclusions on the feedback processes and/or intensity of the ionizing radiation field. The HI-OVI association is enhanced in lower-intensity UVB for simulations having AGN-feedback but the opposite trend is observed for simulations having only stellar-feedback. Analysis of associated absorption in CIV and NeVIII indicates the effect of feedback on different observables is more significant than the effect of UVB, reflecting their physical origin to be high-density-low-temperature and low-density-high-temperature gas respectively. We find OVI originates predominantly in low-density photoionized gas for simulations with AGN-feedback and from higher-density collisionally ionized gas for simulations without it. |
