Measuring Feedback in Damped Lyman Alpha Systems

Abstract

We measure feedback (heating rates) in damped Lyman alpha systems from the cooling rate of the neutral gas. Since cooling occurs through [C II] 158 micron emission, we infer cooling from C II^{*} 1335.7 absorption lines detected with HIRES on the Keck I telescope. The inferred heating rates are about 30 times lower than for the Galaxy ISM. At z = 2.8, the implied star formation rate per unit area is 10^{-2.4+-0.3} solar masses per kpc^{2} per year, and the the star formation rate per unit comoving volume is 10^{-0.8+-0.2} solar masses per Mpc^{3} per year. This is the first measurement of star formation rates in objects likely to be the progenitors of current galaxies.