Detection of interstellar hydrogen peroxide

Abstract

Context. The molecular species hydrogen peroxide, HOOH, is likely to be a key ingredient in the oxygen and water chemistry in the interstellar medium. Aims. Our aim with this investigation is to determine how abundant HOOH is in the cloud core ρ Oph A. Methods. By observing several transitions of HOOH in the (sub)millimeter regime we seek to identify the molecule and also to determine the excitation conditions through a multilevel excitation analysis. Results. We have detected three spectral lines toward the SM1 position of ρ Oph A at velocity-corrected frequencies that coincide very closely with those measured from laboratory spectroscopy of HOOH. A fourth line was detected at the 4σ level. We also found through mapping observations that the HOOH emission extends (about 0.05 pc) over the densest part of the ρ Oph A cloud core. We derive an abundance of HOOH relative to that of H 2 in the SM1 core of about 1 × 10 −10 . Conclusions. To our knowledge, this is the first reported detection of HOOH in the interstellar medium.

Detection of the hydroperoxyl radical HO2towardρOphiuchi A

“…We assume for lines 4 and 5 that the measured flux is coming from the two unresolved hyperfine components proportionally to A ul × g u , as expected for two optically thin lines originating from two levels of the same energy. We assume a source size of 24 , as for hydrogen peroxide (Bergman et al 2011b), and as derived by the analysis of Bergman et al (2011a). We derive a rotational temperature of 16 ± 3 K, slightly lower than the rotational temperature derived for HOOH (22 ± 3 K, Bergman et al 2011b), but marginally consistent with it within the error bars.…”

“…We assume a source size of 24 , as for hydrogen peroxide (Bergman et al 2011b), and as derived by the analysis of Bergman et al (2011a). We derive a rotational temperature of 16 ± 3 K, slightly lower than the rotational temperature derived for HOOH (22 ± 3 K, Bergman et al 2011b), but marginally consistent with it within the error bars. The derived HO 2 column density is (2.8 ± 1.0) × 10 12 cm −2 .…”

“…A significant step in the understanding of water formation was achieved thanks to the detection with APEX of HOOH in Oph A (Bergman et al 2011b This detection has been carefully modeled with an astrochemical model combining reactions in the gas phase and on the grain surfaces based on the hybrid moment equation (HME) method (Du & Parise 2011), applied to the conditions of the Oph A cloud (Du et al 2012). The model successfully reproduces simultaneously the abundances of the observed gas-phase HOOH, O 2 , H 2 CO and CH 3 OH.…”

Multi-line detection of O2towardρOphiuchi A

“…Background image is courtesy of Spitzer IRAC-MIPS (blue: 3.6 μm, green: 8 μm, red: 24 μm). (Liseau et al 2010), N 2 H + (1−0) (di Francesco et al 2004), deuterated molecules (Bergman et al 2011a) and the recently discovered H 2 O 2 (HOOH, Bergman et al 2011b). For the 2.8 km s −1 feature, we are unable to entirely exclude the possibility that it is due to an unidentified species.…”

ExoMol line lists – XV. A new hot line list for hydrogen peroxide

“…Hydrogen peroxide has also been detected in the atmosphere of Europa (Hand & Brown 2013) in the 3.5 µm region. The first detection of interstellar H2O2 was made by Bergman et al (2011) and is believed to play an important role in astrophysical water chemistry similar to that on Earth. Du et al (2012) suggest that H2O2 is produced on dust-grains via the hydrogenation of grain HO2 and released into the gas-phase through surface reactions.…”