Compact dusty clouds and efficient H$_2$ formation in diffuse ISM

TL;DR

This paper investigates how compact dusty clouds in the diffuse interstellar medium enhance molecular hydrogen formation by providing optimal conditions for atomic recombination on dust grains.

Contribution

It introduces the role of compact dusty clouds in increasing H$_2$ formation rates and analyzes the underlying mechanisms and astrophysical implications.

Findings

Compact dusty clouds significantly boost H$_2$ formation in diffuse ISM.

Gaseous clumps around dust clouds facilitate atomic hydrogen recombination.

Enhanced H$_2$ formation impacts interstellar chemistry and star formation processes.

Abstract

The formation of compact dusty clouds in diffuse interstellar medium (ISM) has been recently proposed and studied by Tsytovich et al. (2014). In the present paper, an effect of the clouds on the rate of H$\to$H$_2$ 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 H$_2$ 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 H$_2$ formation enhancement.