Compact Dusty Clouds and Efficient H2 Formation in Diffuse Interstellar Medium

Abstract

The formation of compact dusty clouds in diffuse interstellar medium (ISM) has been recently proposed and studied by Tsytovich et al. In the present paper, the effect of the clouds on the rate of H → H2 transition in the ISM is examined. We discuss the mechanisms leading to the formation of the clouds and the creation of gaseous clumps around them, analyze the main processes determining the efficiency of the recombination of atomic hydrogen on dust grains, and estimate the expected enhancement of the global H2 formation due to the presence of the clouds. In conclusion, we argue that the compact dusty clouds provide optimum conditions for the atomic recombination in diffuse ISM, and point out some astrophysical implications of the resulting H2 formation enhancement. © 2018. The American Astronomical Society. All rights reserved.