J/A+A/597/A45 W51 line of sight deuterium fractionation (Vastel+, 2017)
Deuterium fractionation of a distant cold dark cloud along the line of sight
of W51.
Vastel C., Mookerjea B., Pety J., Gerin M.
<Astron. Astrophys. 597, A45 (2017)>
=2017A&A...597A..45V 2017A&A...597A..45V (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Spectroscopy
Keywords: astrochemistry - line: identification - molecular data -
radiative transfer
Abstract:
Herschel/HIFI observations toward the compact HII region W51 has
revealed the presence of a cold dense core along its line of sight in
a high-velocity stream located just in front of W51. This detection
has been made possible through absorption measurements of low-energy
transitions of HDO, NH3, and C3 against the bright background
emitted by the star-forming region. We present a follow-up study of
this core using the high sensitivity and high spectral resolution
provided by the IRAM 30m telescope. We report new detections of this
core in absorption for DCO+ (2-1, 3-2), H13CO+ (1-0), DNC
(3-2), HN13C (1-0), p-H2CO (20,2-10,1, 30,3-20,2),
and in emission for o-NH2D. We also report interferometric observation
of this last species using the IRAM/NOEMA telescope, revealing the
fragmented nature of the source through the detection of two cores,
separated by 0.19-0.24pc, with average sizes of less than
0.16-0.19pc. From a non-LTE analysis, we are able to estimate the
density (∼2.5x104cm-3) and temperature (∼10K) of this component,
typical of what is found in dark clouds. This component (called
W51-core) has the same DCO+/HCO+ ratio (0.02) as TMC-1 and a high
DNC/HNC ratio (0.14). Detection of these deuterated species indicates
that W51-core is similar to an early-phase low-mass star-forming
region, formed from the interaction between the W51 giant molecular
cloud and the high-velocity stream in front of it. The W51 complex
being at about 5kpc, these findings lead to what is the first
detection of the earliest phase of low-mass star-forming region at
such a large distance.
Description:
The fits file have been generated under the GILDAS CLASS command,
between 40 and 90km/s.
Objects:
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RA (2000) DE Designation(s)
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19 23 50 +14 06.0 W51 = SNR G049.2-00.5
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 118 9 List of fits spectra
fits/* . 9 Individual fits spectra
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See also:
J/ApJS/191/232 : CO survey of W51 molecular cloud (Bieging+, 2010)
J/MNRAS/424/1658 : Molecular clumps in W51 giant mol. cloud (Parsons+, 2012)
J/A+A/582/A64 : W51/e2 and G34.3+0.2 IRAM spectra (Lykke+, 2015)
J/A+A/589/A44 : W51 Main NH3 and CH3OH data cubes (Goddi+, 2016)
J/A+A/595/A27 : JVLA images of W51A (Ginsburg+, 2016)
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- 22 I3 --- Nx Number of pixels along X-axis
24- 46 A23 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.sss)
48- 55 F8.4 GHz bFreq Lower value of frequency interval
57- 63 F7.4 GHz BFreq Upper value of frequency interval
65- 71 F7.1 Hz dFreq Frequency resolution
73- 74 I2 Kibyte size Size of FITS file
76- 88 A13 --- FileName Name of FITS file, in subdirectory fits
90-118 A29 --- Title Title of the FITS file
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Acknowledgements:
Charlotte Vastel, cvastel(at)irap.omp.eu
(End) Patricia Vannier [CDS] 15-Nov-2016