J/A+A/609/A129 HCN, HNC and DNC spectra of 27 sources (Colzi+, 2018)
Nitrogen and hydrogen fractionation in high-mass star forming cores from
observations of HCN and HNC.
Colzi L., Fontani F., Caselli P., Ceccarelli C., Hily-Blant P.,
Bizzocchi L.
<Astron. Astrophys. 609, A129 (2018)>
=2018A&A...609A.129C 2018A&A...609A.129C (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Radio lines
Keywords: radio lines: ISM - ISM: molecules - ISM: abundances
Abstract:
The ratio between the two stable isotopes of nitrogen, 14N and
15N, is well measured in the terrestrial atmosphere (∼272), and for
the pre-solar nebula (∼441, deduced from the solar wind).
Interestingly, some pristine solar system materials show enrichments
in 15N with respect to the pre-solar nebula value. However, it is not
yet clear if and how these enrichments are linked to the past chemical
history because we have only a limited number of measurements in dense
star-forming regions. In this respect, dense cores, which are believed
to be the precursors of clusters and also contain intermediate- and
high-mass stars, are important targets because the solar system was
probably born within a rich stellar cluster, and such clusters are
formed in high-mass star-forming regions. The number of observations
in such high-mass dense cores has remained limited so far. In this
work, we show the results of IRAM-30m observations of the J=1-0
rotational transition of the molecules HCN and HNC and their
15N-bearing counterparts towards 27 intermediate- and high-mass dense
cores that are divided almost equally into three evolutionary
categories: high-mass starless cores, high-mass protostellar objects,
and ultra-compact Hii regions. We have also observed the DNC(2-1)
rotational transition in order to search for a relation between the
isotopic ratios D/H and 14N/15N. We derive average 14N/15N
ratios of 359±16 in HCN and of 438±21 in HNC, with a dispersion of
about 150-200. We find no trend of the 14 N/15 N ratio with
evolutionary stage. This result agrees with what has been found for
N2H+ and its isotopologues in the same sources, although the
14N/15N ratios from N2H+ show a higher dispersion than in HCN/HNC,
and on average, their uncertainties are larger as well. Moreover, we
have found no correlation between D/H and 14N/15N in HNC. These
findings indicate that (1) the chemical evolution does not seem to
play a role in the fractionation of nitrogen, and that (2) the
fractionation of hydrogen and nitrogen in these objects is not
related.
Description:
We performed observations of the J=1-0 rotational transition of
H15NC, HN13C, HC15N and H13CN towards the 27 sources observed
by Fontani et al. (2015ApJ...808L..46F 2015ApJ...808L..46F) from 6 to 9 June, 2015, using
the 3mm receiver of the IRAM-30m telescope.
We simultaneously observed the J=2-1 transition of DNC with the 2mm
receiver.
IRAM-30m Telescope, 1mm and 3mm receivers, fast Fourier transform
spectrometers: FTS50
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sources.dat 142 27 *Total column densities (beam-averaged), of
H15NC, HN13C, DNC (table 3) and HC15N and
H13CN(1-0) transitions (table 4)
dnc/* . 27 DNC spectra
h13cn/* . 27 H13CN spectra
h15nc/* . 27 H15NC spectra
hc15n/* . 27 HC15N spectra
hn13c/* . 27 HN13C spectra
--------------------------------------------------------------------------------
Note on sources.dat: Total column densities computed as explained in Sect. 3.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: sources.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Type Type (HMPO, HMSC or UCHII)
7- 19 A13 --- Source Source name
20 A1 --- n_Source [w] Note on Source (1)
21- 22 A2 --- l_N(H15NC) [≤ ] Limit flag on N(H15NC)
23- 25 I3 10+10cm-2 N(H15NC) Total H15NC column density
(beam-averaged)
27- 28 I2 10+10cm-2 e_N(H15NC) ? rms uncertainty on N(H15NC) (2)
29 A1 --- n_N(H15NC) [ut] Note on N(H15NC) (1)
31- 32 I2 10+10cm-2 DN1 ?=- Error on N(H15NC) without considering
the calibration error
34- 38 F5.1 10+11cm-2 N(HN13C) Total HN13C column density
(beam-averaged)
40- 43 F4.1 10+11cm-2 e_N(HN13C) rms uncertainty on N(HN13C) (2)
45- 47 F3.1 10+11cm-2 DN2 Error on N(HN13C) without considering the
calibration error
49- 52 F4.1 10+11cm-2 N(DNC) Total DNC column density (beam-averaged)
54- 56 F3.1 10+11cm-2 e_N(DNC) rms uncertainty on N(DNC) (2)
58- 59 A2 --- l_HNC/H15NC [≥ ] Limit flag on HNC/H15NC
60- 62 I3 --- HNC/H15NC HNC/H15NC isotopic ratio (3)
64- 66 I3 --- e_HNC/H15NC ? rms uncertainty on HNC/H15NC (2)
68- 71 I4 --- HNC/DNC HNC/DNC isotopic ratio (4)
73- 75 I3 --- e_HNC/DNC rms uncertainty on HNC/DNC (2)
77- 82 E6.2 --- DNC/HNC DNC/HNC isotopic ratio
84- 89 E6.2 --- e_DNC/HNC rms uncertainty on DNC/HNC (2)
91- 92 A2 --- l_N(HC15N) [≤ ] Limit flag on N(HC15N)
93- 96 I4 10+10cm-2 N(HC15N) Total N(HC15N) column density
(beam-averaged)
98-100 I3 10+10cm-2 e_N(HC15N) ? rms uncertainty on N(HC15N)
101 A1 --- n_N(HC15N) [ut] Note on N(HC15N) (1)
103-104 I2 10+10cm-2 DN3 ?=- Error on N(HC15N) without considering
the calibration error
106-108 I3 10+11cm-2 N(H13CN) Total H13CN column density
(beam-averaged)
110-111 I2 10+11cm-2 e_N(H13CN) rms uncertainty on N(H13CN) (2)
113-115 F3.1 10+11cm-2 DN4 Error on N(H13CN) without considering the
calibration error
117-118 A2 --- l_HCN/HC15N [≥ ] Limit flag on HCN/HC15N
119-121 I3 --- HCN/HC15N HCN/HC15N isotopic ratio (3)
123-125 I3 --- e_HCN/HC15N ? rms uncertainty on HCN/HC15N (2)
127-128 I2 K Tk Kinetic temperature of the clump (5)
129 A1 --- n_Tk [*] Note on Tk (6)
131-142 A12 --- FName Name used in the spectra files (7)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
w = "warm" HMSC
u = upper limit
t = tentative detection
Note (2): Uncertainties in the column densities and in the isotope ratios
have been computed as explained in Sect. 3.1 and 3.2.
Note (3): it has been multiplied by 12C/13C as described in Section (3.1).
Note (4): it has been multiplied by 12C/13C and by the correction of the
different beams 3.09.
Note (5): kinetic temperatures of the clumps derived from Fontani et al.
(2015ApJ...808L..46F 2015ApJ...808L..46F): for the sources without a derivation of Tk, the mean
value for that evolutionary stage was taken (for the HMSCs the average was
done without the "warm" ones, i.e those with a Tk<20K).
Note (6): * for average value for the specific evolutionary stage
Note (7): The spectra files are named :
FName-dnc.spt in dnc subdirectory,
FName-h13cn.spt in h13cn subdirectory,
FName-h15cn.spt in 15cnn subdirectory,
FName-hc15n.spt in hc15n subdirectory,
FName-hn13c.spt in hn13c subdirectory.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: dnc/* h13cn/* h15nc/* hc15n/* hn13c/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 E17.13 km/s Vlsr LSR velocity
19- 29 E11.5 K Tmb Beam brightness temperature
32- 41 E10.5 --- Tmbf1 ? Tmb computed in the fit
44- 53 E10.5 --- Tmbf2 ? Tmb computed in the fit
56- 65 E10.5 --- Vlsr2 ? LSR velocity for the possible second
component
68- 77 E10.5 --- Tmbs1 ? Beam brightness temperature for the possible
second component
80- 89 E10.5 --- Tmbs2 ? Tmb computed in the fit for the possible
second component
--------------------------------------------------------------------------------
Acknowledgements:
Laura Colzi, colzi(at)arcetri.astro.it
(End) Laura Colzi [Univ. Florence, Italy], Patricia Vannier [CDS] 20-Nov-2017