Absorption features of high redshift galactic winds

The environment of high-redshift galaxies is characterized by both wind-driven outflowing gas and gravitationally infalling streams. To investigate such galaxy-IGM interplay we have generated synthetic optical absorption line spectra piercing the volume surrounding a starbursting analog of a Lyman Break Galaxy selected in a z ≈ 3 output from a SPH simulation, including a detailed treatment of mechanical feedback from winds. Distributions for several observable species (HI, CIII, CIV, SiII, SiIII, SiIV, OVI, OVII, and OVIII) have been derived by post-processing the simulation outputs. The hot wind material is characterized by the presence of high-ionization species such as OVI, OVII, and OVIII (the latter two observable only in X-ray bands); the colder (T < 10 K) infalling streams can be instead identified by the combined presence of SiII, SiIII, and CIII optical absorption together with OVI that surrounds the cooler gas clumps. However, both line profile and Pixel Optical Depth analysis of the synthetic spectra show that the intergalactic filament in which the wind-blowing galaxy is embedded produces absorption signatures that closely mimic those of the wind environment. We conclude that it is generally very difficult to clearly identify wind-blowing galaxies and their complex gaseous environment at high redshift in optical QSO absorption-line spectra based solely on the observed ion absorption patterns.