Discovery of Fulminic Acid, HCNO, in Dark Clouds

TL;DR

This study reports the first detection of fulminic acid (HCNO) in space, observed in several dark clouds and star-forming regions, and explores its formation mechanisms and abundance ratios relative to HNCO.

Contribution

First detection of HCNO in space, with analysis of its abundance and formation pathways in various interstellar environments.

Findings

HCNO detected in three starless cores and a star-forming region.

Abundance ratio of HNCO/HCNO varies between 40-70 in observed regions.

Reaction CH2 + NO is key to HCNO formation, matching observed abundances.

Abstract

We report on the first detection in space of fulminic acid, HCNO. This isomer of HNCO has been observed in three starless cores, B1, L1544 and L183, and in the low mass star forming region L1527 with a measured abundance ratio of HNCO/HCNO between 40-70. However, HCNO was not detected towards the direction of the cyanopolyyne peak of TMC-1 or towards the Orion Hot Core region. The derived HNCO/HCNO abundance ratio in these cases is greater than 350 and 1000 in TMC-1 and Orion, respectively. We find that CH_2 + NO \to HCNO + H is a key reaction for the formation of fulminic acid. A value of 5.5 10^{-12} cm^3 s^{-1} of the corresponding reaction rate coefficient, as given by Miller et al. (2003), allows to reproduce the observed abundances of fulminic acid in both the observed dark clouds and low mass star forming core, where the determined abundance of HNCO in these regions with respect to molecular hydrogen is 1-5 10^{-10}.