Characterizing the chemical pathways for water formation -- A deep search for hydrogen peroxide

TL;DR

This study searches for hydrogen peroxide in various astrophysical environments, finds it only in Oph A, and explores the conditions favoring its formation, revealing its sensitivity to temperature and the uniqueness of Oph A.

Contribution

It provides the first extensive search for HOOH in diverse sources and analyzes the conditions for its formation, highlighting Oph A's unique chemical environment.

Findings

HOOH detected only in Oph A among surveyed sources.

Upper limits for HOOH abundance are lower in other sources.

HOOH formation is highly temperature-dependent, favoring 20-30 K.

Abstract

In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., A&A, 2011, 531, L8). This detection appeared a posteriori quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3$\sigma$ upper limits for the abundance of HOOH relative to H$_2$ lower than in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the puzzle to why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O$_2$. Our chemical models show that the production of HOOH is extremely sensitive to the temperature, and favored only in the range 20$-$30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20$-$30 K.