Photoelectric heating for dust grains at high redshifts

Abstract

Lyman-a absorption systems at z 3 with N H I 0 3 10 14 cm 2 have been found to be enriched with a mean metallicity of Z=Z 10 2:5 , and a large scatter in the metallicity. It is reasonable to assume that the process of initial enrichment of the intergalactic medium (IGM) at z 0 3 also produced dust grains. We explore the implications of the presence of dust grains in the IGM at high redshift, in particular, the contribution of photoelectric emission from grains by hard background photons to the net heating rate of the IGM.