J/A+A/633/A54 B0355+508 reduced spectra (Chantzos+, 2020)
The first steps of Interstellar Phosphorus Chemistry.
Chantzos J., Rivilla V.M., Vasyunin A., Redaelli E., Bizzocchi L.,
Fontani F., Caselli P.
<Astron. Astrophys. 633, A54 (2020)>
=2020A&A...633A..54C 2020A&A...633A..54C (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Interstellar medium ; Spectroscopy ; Radio lines
Keywords: astrochemistry - line: identification - molecular processes -
ISM: molecules
Abstract:
Phosphorus-bearing species are essential to the formation of life on
Earth, however they have barely been detected in the interstellar
medium. In particular, towards star-forming regions only PN and PO
have been identified so far. Since only a small number of detections
of P-bearing molecules are available, their chemical formation
pathways are not easy to constrain and are thus highly debatable. An
important factor still missing in the chemical models is the initial
elemental abundance of phosphorus, that is, the depletion level of P
at the start of chemical models of dense clouds.
In order to overcome this problem, we study P-bearing species in
diffuse and translucent clouds. In these objects phosphorus is
expected to be mainly in the gas phase and therefore the elemental
initial abundance needed in our chemical simulations corresponds to
the cosmic one and is well constrained.
For the study of P-bearing chemistry we used an advanced chemical
model. We updated and significantly extended the P-chemistry network
based on chemical databases and previous literature. We performed
single-pointing observations with the IRAM 30m telescope in the 3mm
range towards the line of sight to the strong continuum source
B0355+508 aiming for the (2-1) transitions of PN, PO, HCP, and CP.
This line of sight incorporates five diffuse and/or translucent
clouds.
The (2-1) transitions of the PN, PO, HCP, and CP were not detected. We
report high signal-to-noise-ratio detections of the (1-0) lines of
13CO, HNC, and CN along with a first detection of C34S towards
this line of sight. We have attempted to reproduce the observations of
HNC, CN, CS, and CO in every cloud with our model by applying typical
physical conditions for diffuse or translucent clouds. We find that
towards the densest clouds with vLSR= -10, -17 km/s the best-fit
model is given by the parameters (nH, AV, Tgas) = (300cm-3,
3mag, 40K).
According to our best-fit model, the most abundant P-bearing species
are HCP and CP (1e-10). The molecules PN, PO, and PH3 also show
relatively high predicted abundances of 1e-11. We show that the
abundances of these species are sensitive to visual extinction,
cosmic-ray ionization rate, and the diffusion-to-desorption energy
ratio on dust grains. The production of P-bearing species is favored
towards translucent rather than diffuse clouds, where the environment
provides a stronger shielding from the interstellar radiation. Based
on our improved model, we show that the (1-0) transitions of HCP, CP,
PN, and PO are expected to be detectable with estimated intensities of
up to ∼200mK.
Description:
The observations of the HCP (2-1), CP (2-1), PN (2-1) and PO (2-1)
transitions in the 3mm range were carried out at the IRAM 30m
telescope located at Pico Veleta (Spain) towards the line of sight to
the compact extragalactic quasar B0355+508.
Objects:
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RA (2000) DE Designation(s)
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03 59 29.75 +50 57 50.2 B0355+508 = QSO B0355+508
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sp13co.dat 29 271 13CO spectrum towards B0355+508
spc34s.dat 29 237 C34S spectrum towards B0355+508
spcn.dat 29 279 CN spectrum towards B0355+508
sphnc.dat 29 223 CN spectrum towards B0355+508
spcp.dat 29 234 CP spectrum towards B0355+508
sphcp.dat 29 197 HCP spectrum towards B0355+508
sppn.dat 29 231 PN spectrum towards B0355+508
sppo.dat 29 268 PO spectrum towards B0355+508
cnallhyp.dat 29 1978 CN spectra towards B0355+508
pchemnet.dat 114 466 Chemical Network of two-body reactions
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Byte-by-byte Description of file: sp*.dat
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Bytes Format Units Label Explanations
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2- 17 E16.10 km/s Vlsr Velocity
19- 29 E11.4 K TMB Main beam temperature
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Byte-by-byte Description of file: cnallhyp.dat
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Bytes Format Units Label Explanations
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4- 13 F10.3 MHz Freq Frequency
19- 29 E11.4 K TMB Main beam temperature
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Byte-by-byte Description of file: pchemnet.dat
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Bytes Format Units Label Explanations
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3- 10 A8 --- R1 Reactant 1
20- 27 A8 --- R2 Reactant 2
40- 47 A8 --- P1 Product 1
57- 64 A8 --- P2 Product 2
74- 81 A8 --- P3 Product 3
91- 98 E8.2 --- alpha Rate coefficient, in s-1 or cm3/s units
101-105 F5.2 --- beta Rate coefficient, in s-1 or cm3/s units
108-114 F7.1 --- gamma Rate coefficient, in s-1 or cm3/s units
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Acknowledgements:
Johanna Chantzos, chantzos(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 04-Nov-2019