Interaction between Galaxies and the Intergalactic Medium at z = 3

Abstract

In this thesis, we aim to study the clustering properties of galaxies at z ≈ 3 and the relationship between galaxies and the IGM at these redshift via clustering correlation functions. We use the combined data from the VLT LBG Survey (Bielby, 2008) and the Keck survey (Steidel, 2003) to measure the LBG-LBG correlation function. We aim to estimate the infall parameter, β from the ratio of LBG-LBG correlation function in redshift space, ξ (s), and in real space, ξ (r). We found agreement with Bielby et al. (2008) in the ξ (s) result from the VLT data. Our LBG-LBG ξ (s) from the combined data is consistent with the observed ξ (s) from da Angela et al. (2005), where γ = 1.71 and s0 = 5.1 h−1 Mpc. We also tested the effect of redshift errors by using the z−space distortions model from da Angela et al. (2005) with our parameters. We found the peculiar velocities had a smaller effect in the combined data compared to only VLT data. This may be because smaller redshift errors in Steidel et al. (2003). By computing and fitting ξ (s)/ξ (r), we get β = 0.14 at z = 3. This gives a bias factor, b = 6.8. This result agrees with Bielby et al. (2008), β = 0.21 , estimated by fitting the power-law ξ (r) to the measurement of ξ (σ, π) from the combined data.

We then calculate the Lyα-LBG and LBG-CIV correlation function. We attempt to (a) investigate the effect of feedback on the LBG-Lyα cross correlation, (b) compare the LBG-CIV cross-correlation with LBG-LBG ξ (s) to see if CIV absorption systems are distributed like LBGs. We use a different approach to reanalyze the Lyα-LBG ξ (s), with different ways of estimating the error to compare our result with Bielby et al. (2008). Our results agree with those of Bielby et al. (2008) but with slightly smaller error bars. Results
from high and low resolution QSO spectra are compared to the results of Adelberger et al. (2003) and Adelberger et al. (2005). We found a decrease in transmissivity at distances below 3 h−1 Mpc and an increase of < flux/cont > to the mean value at larger scales.We detected how these results were affected by the LBG velocity dispersion found in Chapter 3. We also perform CIV-LBG cross correlation. It is consistent with the LBG- LBG auto-correlation function. This is consistent with CIV systems and LBGs being the same objects as they show the same clustering behaviour.

We then employed the GIMIC simulations to create synthetic Lyα spectra and Galaxies. Our main aims are to study (a) the LBG-LBG ξ (s) to see if we can detect the effects of peculiar velocities by comparing real and redshift space correlation functions, (b) the LBG-Lyα ξ (s) to understand more about outflow and feedback. We selected galaxies in the simulation by stellar mass. From our results, the LBG-LBG correlation functions in real and redshift space tend to appear as power laws. The effect of peculiar velocities in redshift space has been detected since the LBG-LBG ξ (s) in redshift space tends to have lower clustering than ξ (r) in real space at small scales. From the LBG-Lyα ξ (s), we found a decrease in <flux/cont> at separations below 5 h−1 Mpc. ξ (s) increases and reaches the mean value at <flux/cont> ≈ 0.70 at larger scales. At small distances near LBGs, we see no effect from the wind from the simulations. The results seem to agree with Adelberger et al. (2005) rather than Adelberger et al. (2003). Therefore they are less in agreement with our VLT results which show some evidence for feedback at small scales.