J/MNRAS/478/3693 N in Galactic high-mass star-forming cores (Colzi+, 2018)
Nitrogen fractionation in high-mass star-forming cores across the Galaxy.
Colzi L., Fontani F., Rivilla V.M., Sanchez-Monge A., Testi L.,
Beltran M.T., Caselli P.
<Mon. Not. R. Astron. Soc., 478, 3693-3720 (2018)>
=2018MNRAS.478.3693C 2018MNRAS.478.3693C (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Star Forming Region ; Abundances
Keywords: stars: formation - stars: massive - ISM: abundances - ISM: molecules -
primordial nucleosynthesis
Abstract:
The fractionation of nitrogen (N) in star-forming regions is a poorly
understood process. To put more stringent observational constraints on
the N-fractionation, we have observed with the IRAM-30-m telescope a
large sample of 66 cores in massive star-forming regions. We targeted
the (1-0) rotational transition of HN13C, HC15N, H13CN and
HC15N, and derived the 14N/15N ratio for both HCN and HNC. We
have completed this sample with that already observed by Colzi et al.,
and thus analysed a total sample of 87 sources. The 14N/15N ratios
are distributed around the Proto-Solar Nebula value with a lower limit
near the TA value (∼272). We have also derived the 14N/15N
ratio as a function of the Galactocentric distance and deduced a
linear trend based on unprecedented statistics. The Galactocentric
dependences that we have found are consistent, in the slope, with past
works but we have found a new local 14N/15N value of ∼400,
i.e. closer to the Prosolar Nebula value. A second analysis was done,
and a parabolic Galactocentric trend was found. Comparison with
Galactic chemical evolution models shows that the slope until 8 kpc is
consistent with the linear analysis, while the flattening trend above
8 kpc is well reproduced by the parabolic analysis.
Description:
The 67 sources analysed in this work were observed with the IRAM-30-m
telescope in 2014 August. We have used the FTS spectrometer (Fast
Fourier Transform Spectrometer) to cover the frequency range
85.7-93.5GHz with a frequency resolution of 200kHz, corresponding
to 0.6km/s at the observed frequencies.
We have observed the rotational transitions J=1-0 of HN13C,
H15NC, H13CN and HC15N towards 67 massive star-forming cores to
derive the 14N/15N ratios.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 67 67 List of the observed sources
table3.dat 86 67 Total column densities of observed transitions
and 14N/15N ratios
tablea1.dat 68 67 Values obtained with the fitting procedure
described in Section 3 to the HN13C lines
tablea2.dat 67 67 Values obtained with the fitting procedure
described in Section 3 to the H15NC(1-0) lines
tablea3.dat 67 67 *Values obtained with the fitting procedure
described in Section 3 to the H13CN lines
tablea4.dat 66 66 Values obtained with the fitting procedure
described in Section 3 to the HC15N(1-0) lines
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Note on tablea3.dat: Note that in some cases (e.g. 18310-0825M3) for the two
isotopologues the fitted line width can be different and this can be explained
by a higher rms in a spectrum than in the other cases. The higher rms noise
worsen the S/N for the 15N-isotopologues which have weaker emission lines
with respect to 13C-isotopologues.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Source Source name
13- 14 A2 --- n_Source [* ] Note on Source (1)
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 25 F4.1 s RAs Right ascension (J2000)
27 A1 --- DE- Declination sign (J2000)
28- 29 I2 deg DEd Declination (J2000)
31- 32 I2 arcmin DEm Declination (J2000)
34- 37 F4.1 arcsec DEs Declination (J2000)
39- 44 F6.2 deg GLON Galacitc longitude
46- 50 F5.2 deg GLAT Galacitc latitude
52- 55 F4.1 kpc Dist Galactocentric distance of the source obtained
from the distance to the Sun of the
associated star-forming region
56 A1 --- n_Dist [* ] Note ob dist (1)
58- 61 F4.1 kpc DGC Galactocentric distance
63- 64 I2 K Tex ?=- Excitation temperature (2)
65- 67 A3 --- n_Tex [* ] Note on Tex (1)
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Note (1): Notes as follows:
* = Sources with distance ambiguity, due to their position within the solar
circle, for which we have chosen the near distance. For details see
Sridharan et al. (2002ApJ...566..931S 2002ApJ...566..931S).
** = Sources selected from the literature (Wouterloot et al., 1993,
Cat. J/A+AS/98/589; Fontani et al. (2011A&A...529L...7F 2011A&A...529L...7F);
Tan et al. (2014, Protostars and Planets VI, p. 149);
Beltran et al. (2016, AR&A, 24, 6);
Cesaroni et al. (2017A&A...602A..59C 2017A&A...602A..59C).
*** = Sources for which it was not possible to obtain Tex from CH3CN and
then we have used a Tex of 35K, which is the mean value of the
excitation temperatures of the sources.
Note (2): Tex used to fit the lines for all the sources, computed as explained
in Section 3. The Tex have been derived fitting the K-ladder of CH3CN(5-4)
(Mininni et al., in preparation).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Source Source name
14- 15 A2 --- l_N(HN13C) [≤ ] Limit flag on N(HN13C)
16- 19 F4.1 10+12cm-2 N(HN13C) ?=- HN13C total column density
(beam-averaged) (1)
21- 23 F3.1 10+12cm-2 e_N(HN13C) ? rms uncertainty on N(HN13C)
25- 26 A2 --- l_N(H15NC) [≤ ] Limit flag on N(H15NC)
27- 30 F4.1 10+11cm-2 N(H15NC) ?=- H15NC total column density
(beam-averaged) (1)
32- 35 F4.1 10+11cm-2 e_N(H15NC) ? rms uncertainty on N(H15NC)
36 A1 --- n_N(H15NC) [t] Note on N(H15NC) (G1)
37- 38 A2 --- l_N(H13CN) [≤ ] Limit flag on N(H13CN)
39- 43 F5.1 10+12cm-2 N(H13CN) ?=- H13CN total column density
(beam-averaged) (1)
45- 48 F4.1 10+12cm-2 e_N(H13CN) ? rms uncertainty on N(H13CN)
50- 51 A2 --- l_N(HC15N) [≤ ] Limit flag on N(HC15N)
52- 56 F5.1 10+11cm-2 N(HC15N) ?=- HC15N total column density
(beam-averaged) (1)
58- 61 F4.1 10+11cm-2 e_N(HC15N) ? rms uncertainty on N(HC15N)
62 A1 --- n_N(HC15N) [t] Note on N(HC15N) (G1)
64- 65 A2 --- l_HNC/H15NC [<≥ ] Limit flag on HNC/H15NC
66- 68 I3 --- HNC/H15NC ?=- HNC/H15NC ratio
70- 72 I3 --- e_HNC/H15NC ? rms uncertainty on HNC/H15NC
74- 75 A2 --- l_HNC/HC13N [<≥ ] Limit flag on HNC/HC13N
76- 79 I4 --- HNC/HC13N ?=- HNC/HC13N ratio
81- 83 I3 --- e_HNC/HC13N ? rms uncertainty on HNC/HC13N
85- 86 I2 --- 12C/13C 12C/13C ratio
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Note (1): computed as explained in Section 3.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Source Source name
16- 22 F7.3 km/s vLSR ?=- HN13C(1-0) LSR centroid velocity
24- 27 F4.2 km/s e_vLSR ? rms uncertainty on vLSR
31- 34 F4.2 km/s Dv1/2 ?=- HN13C(1-0) FWHM
36- 39 F4.2 km/s e_Dv1/2 ? rms uncertainty on Dv1/2
41- 42 A2 --- l_Ntot [≤ ] Limit flag on Ntot
43- 46 F4.1 10+12cm-2 Ntot ?=- Total column density
48- 50 F3.1 10+12cm-2 e_Ntot ? rms uncertainty on Ntot
53- 58 F6.4 --- tau ?=- Opacity of the line
60- 65 F6.4 --- e_tau ? rms uncertainty on tau
67- 68 I2 mK sigma rms of observed line
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Source Source name
15- 20 F6.2 km/s vLSR ?=- H15NC(1-0) LSR centroid velocity
22- 25 F4.2 km/s e_vLSR ?=- rms uncertainty on vLSR
26- 27 A2 --- l_Dv1/2 [≤ ] Limit flag on Dv1/2
28- 31 F4.2 km/s Dv1/2 ?=- H15NC(1-0) FWHM
33- 36 F4.2 km/s e_Dv1/2 ? rms uncertainty on Dv1/2
38- 39 A2 --- l_Ntot [≤ ] Limit flag on Ntot
40- 43 F4.1 10+12cm-2 Ntot ?=- Total column density
45- 48 F4.1 10+12cm-2 e_Ntot ? rms uncertainty on Ntot
49 A1 --- n_Ntot [t] Note on Ntot (G1)
52- 57 F6.4 --- tau ?=- Opacity of the line
59- 64 F6.4 --- e_tau ? rms uncertainty on tau
66- 67 I2 mK sigma rms of observed line
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Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Source Source name
15- 20 F6.2 km/s vLSR ?=- H15NC(1-0) LSR centroid velocity
22- 25 F4.2 km/s e_vLSR ? rms uncertainty on vLSR
27- 30 F4.2 km/s Dv1/2 ?=- H15NC(1-0) FWHM
32- 35 F4.2 km/s e_Dv1/2 ? rms uncertainty on Dv1/2
37- 38 A2 --- l_Ntot [≤ ] Limit flag on Ntot
39- 43 F5.1 10+12cm-2 Ntot ?=- Total column density
45- 48 F4.1 10+12cm-2 e_Ntot ? rms uncertainty on Ntot
52- 57 F6.4 --- tau ?=- Opacity of the line
59- 64 F6.4 --- e_tau ? rms uncertainty on tau
66- 67 I2 mK sigma rms of observed line
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Source Source name
15- 20 F6.2 km/s vLSR ?=- HC15N(1-0) LSR centroid velocity
22- 25 F4.2 km/s e_vLSR ? rms uncertainty on vLSR
27- 30 F4.2 km/s Dv1/2 ?=- HC15N(1-0) FWHM
32- 35 F4.2 km/s e_Dv1/2 ? rms uncertainty on Dv1/2
37- 38 A2 --- l_Ntot [≤ ] Limit lfag on Ntot
39- 43 F5.1 10+12cm-2 Ntot ?=- Total column density
45- 48 F4.1 10+12cm-2 e_Ntot ? rms uncertainty on Ntot
49 A1 --- n_Ntot [t] Note on Ntot (G1)
51- 56 F6.4 --- tau ?=- Opacity of the line
58- 63 F6.4 --- e_tau ? rms uncertainty on tau
65- 66 I2 mK sigma rms of observed line
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Global notes:
Note (G1): Note as follows:
t = Tentative detection, as explained in Section 3
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Aug-2021