Search for HOOH in Orion

Journal article, 2015

Context. The abundance of key molecules determines the level of cooling that is necessary for the formation of stars and planetary systems. In this context, one needs to understand the details of the time dependent oxygen chemistry, leading to the formation of O-2 and H2O. Aims. We aim to determine the degree of correlation between the occurrence of O-2 and HOOH (hydrogen peroxide) in star-forming molecular clouds. We first detected O-2 and HOOH in rho Oph A, we now search for HOOH in Orion OMCA, where O-2 has also been detected. Methods. We mapped a 3' x 3' region around Orion H-2-Peak 1 with the Atacama Pathfinder Experiment (APEX). In addition to several maps in two transitions of HOOH, viz. 219.17 GHz and 251.91 GHz, we obtained single-point spectra for another three transitions towards the position of maximum emission. Results. Line emission at the appropriate LSR-velocity (Local Standard of Rest) and at the level of >= 4 sigma was found for two transitions, with lower signal-to-noise ratio (2.8-3.5 sigma) for another two transitions, whereas for the remaining transition, only an upper limit was obtained. The emitting region, offset 18 '' south of H2-Peak 1, appeared point-like in our observations with APEX. Conclusions. The extremely high spectral line density in Orion makes the identification of HOOH much more difficult than in rho Oph A. As a result of having to consider the possible contamination by other molecules, we left the current detection status undecided.