Volume 520, September-October 2010
|Number of page(s)||20|
|Section||Interstellar and circumstellar matter|
|Published online||23 September 2010|
Table A.1: HCO+ (0-1) absorption line analysis results.
Table A.2: HNC (0-1) absorption line analysis products.
Table A.3: HCN (0-1) absorption line analysis products.
Table A.4: CN (0-1) absorption line analysis products.
Tables A.1-A.4 contains the
results of the Gaussian
decompostion procedure that we have applied to the spectra. The column
densities, given in the last columns, are derived assuming a single
for all the levels of a given molecule as
where , , and are the rest frequency, the upper and lower level degeneracies and the Einstein's coefficients of the observed transition, is the partition funtion, and c is the speed of light. We also remind that for a Gaussian profile of peak opacity and FWHM , the opacity integral is . For an excitation temperature of 2.73 K, Eq. (A.1) becomes
using the HCO+ J=0-1, HNC J=0-1, HCN J,F=0,1-1,2, and CN J,F1,F=0,1/2,3/2-1,1/2,3/2 transitions respectively.
In a spectrum, the possible velocity substructures are systematically
erased due to the finite velocity resolution
This could be
modelled as an uncertainty on the velocity position of each point.
Unfortunately the errors on the abscissa are rarely included in
procedures because the system is considerably heavier to solve and
often prevents convergence. To evaluate the resulting uncertainties on
parameters, namely the central opacity, the velocity centroid, and the FWHM,
we apply the fitting procedure on 3000 synthetic spectra of FWHM
between 0.3 and 3.4 km s-1 sampled with
spectral resolution of the observations
km s-1. A noise is added to
the x-coordinates of all the spectral points. The
rms of all
the measured linewidths
is found to scale as
and decreases from 0.04 to 0.01 km s-1 as the true linewidth increases from 0.3 to 3.4 km s-1. These uncertainties are smaller than (or comparable to) those inferred from the fitting procedure and the resulting errors on the column densities are at most 12%. In comparison the resulting errors on central opacities and velocity centroids are negligible.
Table C.1: Rates k of the main reactions of the cyanide chemistry.
show the main production and destruction pathways of the hydrogenation
chains of carbon, nitrogen, and
cyano, resulting from the PDR (
AV = 0.4)
AV = 0.4,
= 10-11 s-1)
respectively. These figures are simplified: for each species, only the
reactions which altogether contribute at least to 70 percent of the
total destruction and formation rate are displayed. There is one major
difference between these networks: in a UV-dominated chemical model,
the cyanide chemistry is initiated by:
while in a chemistry driven by turbulent dissipation, the hydrogenation chain of cyano is triggered by the ion-neutral reactions:
Since the pathways displayed in Figs. C.1 and C.2 depend on the chemical rates, and since the nitrogen and cyanide chemistry are still poorly known, we list the chemical rates we have adopted in our models for several reactions in Table C.1.
Chemical network of a UV-dominated chemistry: = 50 cm-3 and AV = 0.4. This figure is simplified: for each species, only the reactions which altogether contribute at least to 70 percent of the total destruction and formation rate are displayed. The red arrow show the endoenergetic reactions with the energy involved.
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Same as Fig. C.1 for a turbulence-dominated chemistry: = 50 cm-3, AV = 0.4 and a = 10-11 s-1. For the sake of simplicity, the main destruction route of N (N + CH2+ HCN+ + H) and the main formation pathway of N+ (photodissociation of NO+) are not displayed here: those two species are therefore highlighted.
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