Dust absorption along the line of sight for high-redshift objects

Abstract

We estimate the optical depth distribution of dust present in absorption systems along the line of sight of high redshift galaxies and the resulting reddening. We characterize the probability distribution of the transmission to a given redshift and the shape of the effective mean extinction law by means of analytical estimates and Monte Carlo simulations. We present our results in a format useful for applications to present samples of high redshift galaxies and discuss the implications for observations with the James Webb Space Telescope. Our most realistic model takes into account the metallicity evolution of Damped Lyman Alpha absorbers and predicts that the effects of dust absorption are modest: at redshift z \gtrsim 5 the transmission is above 0.8 at an emitted wavelength λ_e = 0.14 μm with probability 90%. Therefore dust obscuration along the line of sight will affect only marginally observations at very high redshift.