2002ApJ...578..211S


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.29CET00:51:44

2002ApJ...578..211S - Astrophys. J., 578, 211-223 (2002/October-2)

Galactic 12C/13C ratios from millimeter-wave observations of interstellar CN.

SAVAGE C., APPONI A.J., ZIURYS L.M. and WYCKOFF S.

Abstract (from CDS):

The N=1⟶0 transitions of 12CN and 13CN(X 2Σ+) at 113.5 and 108.8 GHz, respectively, have been observed in a sample of 13 Galactic molecular clouds using the Kitt Peak 12 m radio telescope. The objects studied include the Galactic center [SgrB2(OH)], sources in the solar neighborhood such as Orion A and NGC 2024, and various other clouds with and without star formation. Hyperfine structure, arising from the nitrogen nuclear spin, was resolved in the spectra of both species, enabling an accurate determination of the opacity in 12CN. From these measurements, estimates of the 12C/13C isotope ratio were obtained. These values fall in the range 12C/13C∼20-70 and exhibit a noticeable gradient with distance from the Galactic center. In general, the ratios obtained from CN are very similar to those determined from millimeter observations of CO but are consistently lower than those derived from H2CO. If chemical fractionation is occurring in CN, it is comparable to that in CO. The highest 12C/13C ratios (65±12 and 70±11) were obtained toward two known photon-dominated regions (the Orion Bar and NGC 2024); CN in these two sources may be undergoing some isotope-selective photodissociation. The 12C/13C ratio of 43±7, found in Orion A, is similar to that determined from optical observations of CN toward a nearby source, ζ Ophiuchi, but significantly lower than the average value found in comets (90±10). This difference suggests that substantial enrichment of 13C has occurred during the past 4.6 Gyr in the solar neighborhood.

Abstract Copyright:

Journal keyword(s): Astrochemistry - Galaxy: Abundances - ISM: Abundances - ISM: Clouds - ISM: Molecules - Radio Lines: ISM

Simbad objects: 19

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Number of rows : 19

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME W 3 OH HII 02 27 04.1 +61 52 22           ~ 947 2
2 TMC-1 MoC 04 41 45.9 +25 41 27           ~ 1382 0
3 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2031 1
4 [RLK73] IRc 2 IR 05 35 14.51548 -05 22 30.5943           ~ 582 1
5 M 42 HII 05 35 17.3 -05 23 28           ~ 3756 0
6 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 734 0
7 NAME Ori A MoC 05 38 -07.1           ~ 2705 0
8 NGC 2024 Cl* 05 41 43 -01 50.5           ~ 1077 1
9 LDN 183 MoC 15 54 12.2 -02 49 42           ~ 690 1
10 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1739 2
11 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11831 0
12 NAME Sgr B2 (OH) MoC 17 47 20.8 -28 23 32           ~ 80 0
13 SNR G012.8-00.2 SFR 18 14 14.0 -17 55 50           ~ 221 0
14 OH 34.26 +0.15 SFR 18 53 18.54 +01 14 57.9           ~ 468 0
15 W 49 SFR 19 10 20 +09 07.7           ~ 514 1
16 NAME W 51 Main reg 19 23 43.8 +14 30 37           ~ 131 0
17 W 51 SNR 19 23 50 +14 06.0           ~ 1160 1
18 [MBS2007c] CygX-N44 Rad 20 39 01.01 +42 22 50.2           ~ 363 0
19 NGC 7538 OpC 23 13 37 +61 30.0           ~ 831 0

    Equat.    Gal    SGal    Ecl

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2020.11.29-00:51:44

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