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 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 2014ApJ...793..111C) was observed with the Atacama Pathfinder
Experiment(APEX, http://www.apex-telescope.org/) 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 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 (http://www.ira.inaf.it/~brand/gag.html) and xs
(ftp://yggdrasil.oso.chalmers.se/pub/xs/). All our data are
retrievable from the ESO Science Archive APEX
(http://archive.eso.org/wdb/wdb/eso/apex/form).
Objects:
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RA (ICRS) DE Designation(s)
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05 35 13.57 -05 22 03.8 Orion H2-Peak 1 = NAME ORION PEAK 1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 159 10 List of fits files
fits/* . 10 Individual fits files
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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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 (YYYY-MM-DDThh:mm:ss.ss)
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
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Acknowledgements:
Rene Liseau, rene.liseau(at)chalmers.se
(End) Patricia Vannier [CDS] 21-Oct-2015