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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 (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) 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/* 89 27 DNC spectra h13cn/* 89 27 H13CN spectra h15nc/* 89 27 H15NC spectra hc15n/* 89 27 HC15N spectra hn13c/* 89 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): 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)
(End) Laura Colzi [Univ. Florence, Italy], Patricia Vannier [CDS] 20-Nov-2017
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