Microwave Background Anisotropies Due to the Kinematic Sunyaev-Zel'dovich Effect of the Lyman-alpha Forest

Abstract

The Lyman-alpha absorption systems observed in the spectra of QSOs are likely to possess bulk peculiar velocities. The free electrons in these systems scatter the microwave background and distort its spectrum through the kinematic Sunyaev-Zel&#39;dovich effect. I calculate the temperature fluctuations of the microwave sky due to variations in the number of Lyman-alpha systems along different lines-of-sight throughout the universe. The known population of absorbers out to z=5 introduces anisotropies on angular scales <1&#39; with an rms amplitude of order (DeltaT/T)= 10^{-6}*(Omega_Lya/0.05)*(v/400km/s), where Omega_Lya is the cosmological density parameter of ionized gas in Lyman-alpha absorption systems, and v is the rms line-of-sight peculiar velocity of these systems at z=3. Detection of this signal will provide valuable information about the cosmic velocity field and the gas content of Lyman-alpha absorption systems at high redshifts.