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J/A+A/583/A53       Search for H2O2 in Orion                     (Liseau+, 2015)

Search for H2O2 in Orion. Liseau R., Larsson B. <Astron. Astrophys. 583, A53 (2015)> =2015A&A...583A..53L (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; YSOs Keywords: astrochemistry - ISM: general - ISM: individual objects: Orion H2-Peak 1 - ISM: molecules - ISM: abundances - stars: formation Abstract: 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 molecular oxygen and water. We aim to determine the degree of correlation between the occurrence of O2 and HOOH (hydrogen peroxide) in star-forming molecular clouds. We first detected O2 and HOOH in the rho Ophiuchi cloud (core A), we now search for HOOH in Orion Molecular Cloud OMC A, where O2 has also been detected. We mapped a 3x3arcmin2 region around Orion H2-Peak 1 with the Atacama Pathfinder Experiment (APEX). In addition to several maps in two transitions of HOOH, viz. 219.17GHz and 251.91GHz, we obtained single-point spectra for another three transitions towards the position of maximum emission. Line emission at the appropriate LSR-velocity (Local Standard of Rest) and at the level of greater or equal to 4σ was found for two transitions, with lower S/N (2.8-3.5σ) for another two transitions, whereas for the remaining transition, only an upper limit was obtained. The emitting region, offset 18arcsec 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. Description: The region around the position "Orion H2-Peak 1" (Chen et al., 2014ApJ...793..111C) was observed with the Atacama Pathfinder Experiment(APEX, in 2014 during the time August to December (Table 1). APEX is a 12m single dish telescope at 5100m altitude in northern Chile. We used two receivers from the SHeFI1 suite, i.e., APEX-1 for (303-211) 219GHz and (615-505) 252GHz and APEX-2 for (404-312) 269GHz and (505-413), (514-606) 319GHz, respectively (Energyy level diagrams are found in Bergman et al., 2011A&A...531L...8B). At these frequencies, the HPBW of APEX is 20" to 28". The rms value of the telescope pointing accuracy is 2". Maps were obtained on-the-fly in the 219GHz and 252GHz lines, with a sampling rate of 9"/pix,oversampling the 3'x3' region in these lines. Toward the offset position (0", -18"), single position spectra were obtained at 269GHz and 319GHz. For the instantaneous bandwidth of 2.5GHz, we used as backend the Fast Fourier Transform Spectrometer (FFTS) with 32768 spectral channels. We selected a spectral resolution of 76.3kHz per channel, corresponding to a velocity resolution of about ∼0.1km/s. The data were reduced with the software packages GILDAS/CLASS ( and xs ( All our data are retrievable from the ESO Science Archive APEX ( Objects: ----------------------------------------------------------------- RA (ICRS) DE Designation(s) ----------------------------------------------------------------- 05 35 13.57 -05 22 03.8 Orion H2-Peak 1 = NAME ORION PEAK 1 ----------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 159 10 List of fits files fits/* 0 10 Individual fits files
Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 24 I5 --- Nx Number of pixels along X-axis 26- 27 I2 --- Ny ? Number of pixels along Y-axis 29- 33 I5 --- Nz ? Number of slices for datacubes 35- 57 A23 --- Date Observation date ( 59- 70 E12.6 Hz bFreq Lower value of frequency interval 72- 82 E11.6 Hz BFreq Upper value of frequency interval 84- 90 F7.1 Hz dFreq Frequency resolution 92- 96 I5 Kibyte size Size of FITS file 98-120 A23 --- FileName Name of FITS file, in subdirectory fits 122-159 A38 --- Title Title of the FITS file
Acknowledgements: Rene Liseau, rene.liseau(at)
(End) Patricia Vannier [CDS] 21-Oct-2015
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