PRECISE OBSERVATIONS OF THE 12C/13C RATIOS OF HC3N IN THE LOW-MASS STAR-FORMING REGION L1527

Araki, Mitsunori; Takano, Shuro; Sakai, Nami; Yamamoto, Satoshi; Oyama, Takahiro; Kuze, Nobuhiko; Tsukiyama, Koichi

doi:10.3847/1538-4357/833/2/291

Cited by 27 publications

(33 citation statements)

References 56 publications

(90 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This kind of anomaly, known as isotopic fractionation, has been reported and studied, not only in HC3N but also in HC5N and other carbon-chain molecules, in several hot and cold sources (e.g. Takano et al 1998;Sakai et al 2007Sakai et al , 2013Li et al 2016;Araki et al 2016;Taniguchi et al 2016aTaniguchi et al ,b, 2017. The relative abundances ratios of the 13 C isotopologues can be also calculated using column densities estimated from the most conspicuous transitions assuming LTE conditions (see Table 2).…”

Section: Isotopic Fractionation and Astrochemical Implicationsmentioning

confidence: 92%

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Duronea

Bronfman

Mendoza³

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Using APEX-1 and APEX-2 observations, we have detected and studied the rotational lines of the HC 3 N molecule (cyanoacetylene) in the powerful outflow/hot molecular core G331.512-0.103. We identified thirty-one rotational lines at J levels between 24 and 39; seventeen of them in the ground vibrational state v=0 (9 lines corresponding to the main C isotopologue and 8 lines corresponding to the 13 C isotopologues), and fourteen in the lowest vibrationally excited state v 7 =1. Using LTE-based population diagrams for the beam-diluted v=0 transitions, we determined T exc =85±4 K and N (HC 3 N)=(6.9±0.8)×10 14 cm −2 , while for the beam-diluted v 7 =1 transitions we obtained T exc =89±10 K and N (HC 3 N)=2±1×10 15 cm −2 . Non-LTE calculations using H 2 collision rates indicate that the HC 3 N emission is in good agreement with LTE-based results. From the non-LTE method we estimated T kin ≃90 K, n(H 2 )≃2×10 7 cm −3 for a central core of 6 arcsec in size. A vibrational temperature in the range from 130 K to 145 K was also determined, values which are very likely lower limits. Our results suggest that rotational transitions are thermalized, while IR radiative pumping processes are probably more efficient than collisions in exciting the molecule to the vibrationally excited state v 7 =1. Abundance ratios derived under LTE conditions for the 13 C isotopologues suggest that the main formation pathway of HC 3 N is C 2 H 2 + CN → HC 3 N + H.

show abstract

Section: Isotopic Fractionation and Astrochemical Implicationsmentioning

confidence: 92%

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Duronea

Bronfman

Mendoza³

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…It has been suggested that the analogous exchange reaction of 13 C + with 12 CN could produce the observed (relative) 13 C enrichment of the CN group in cyanopolyynes (Takano et al 1998;Araki et al 2016), but the viability of this mechanism has yet to be conclusively demonstrated in dense molecular clouds. Based on the relative similarities of the 12 C/ 13 C ratios in the different C atoms of HC 5 N in TMC-1, Taniguchi et al (2016) deduced that the main route to synthesizing the observed HC 5 N is via hydrocarbon ion (plus N-atom) chemistry.…”

Section: New Hc7n Isotopologuesmentioning

confidence: 99%

“…Depleted 12 C/ 13 C ratios have previously been observed in TMC-1 for the closely related molecules HC 3 N and HC 5 N, as well as CCH and CCS (Sakai et al 2013). Modeling efforts are in progress to understand this isotopic depletion, which seems to be a common characteristic of carbon chains in cold interstellar gas (Yoshida et al 2015;Araki et al 2016).…”

Section: New Hc7n Isotopologuesmentioning

confidence: 99%

Deep K-band Observations of TMC-1 with the Green Bank Telescope: Detection of HC₇O, Nondetection of HC₁₁N, and a Search for New Organic Molecules

Cordiner

Charnley²,

Kisiel

et al. 2017

ApJ

View full text Add to dashboard Cite

The 100 m Robert C. Byrd Green Bank Telescope K-band (KFPA) receiver was used to perform a highsensitivity search for rotational emission lines from complex organic molecules in the cold interstellar medium towards TMC-1 (cyanopolyyne peak), focussing on the identification of new carbon-chain-bearing species as well as molecules of possible prebiotic relevance. We report a detection of the carbon-chain oxide species HC 7 O and derive a column density of (7.8 ± 0.9) × 10 11 cm −2 . This species is theorized to form as a result of associative electron detachment reactions between oxygen atoms and C 7 H − , and/or reaction of C 6 H 2 + with CO (followed by dissociative electron recombination). Upper limits are given for the related HC 6 O, C 6 O and C 7 O molecules. In addition, we obtained the first detections of emission from individual 13 C isotopologues of HC 7 N, and derive abundance ratios HC 7 N/HCCC 13 CCCCN = 110 ± 16 and HC 7 N/HCCCC 13 CCCN = 96 ± 11, indicative of significant 13 C depletion in this species relative to the local interstellar elemental 12 C/ 13 C ratio of 60-70. The observed spectral region covered two transitions of HC 11 N, but emission from this species was not detected, and the corresponding column density upper limit is 7.4 × 10 10 cm −2 (at 95% confidence). This is significantly lower than the value of 2.8 × 10 11 cm −2 previously claimed by Bell et al. (1997) and confirms the recent non-detection of HC 11 N in TMC-1 by Loomis et al. (2016). Upper limits were also obtained for the column densities of malononitrile and the nitrogen heterocycles quinoline, isoquinoline and pyrimidine.

show abstract

“…For example, in HC 3 N, the 12 C/ 13 C ratio is ∼85-86 if the two acetylenic carbons are considered, but the value decreases to ∼64 for the CN moiety. These varying ratios are attributed to gas-phase chemical fractionation in formation processes, and require low temperatures near T ∼ 10 K, as found in the starless cores in sources like TMC-1 (e.g., Araki et al 2016). In Orion-KL, the 12 C/ 13 C ratios for HC 3 N and its isotopologues vary greatly depending on the carbon atom and on the region of the cloud.…”

Section: Introductionmentioning

confidence: 99%

“…Not all measurements of 12 C/ 13 C ratios are suitable for Galactic gradient determinations, however. In cold, dark clouds, such as TMC-1 and L1527, carbon isotope anomalies have been observed in various long-chain molecules, e.g., HC 3 N, C 4 H, and C 3 S (e.g., Sakai et al 2013;Araki et al 2016). Differing 12 C/ 13 C ratios are obtained, depending on the carbon atom.…”

Section: Introductionmentioning

confidence: 99%

The ¹²C/¹³C Ratio in Sgr B2(N): Constraints for Galactic Chemical Evolution and Isotopic Chemistry

Halfen

Woolf

Ziurys

2017

ApJ

View full text Add to dashboard Cite

A study has been conducted of 12 C/ 13 C ratios in five complex molecules in the Galactic center. H 2 CS, CH 3 CCH, NH 2 CHO, CH 2 CHCN, and CH 3 CH 2 CN and their 13 C-substituted species have been observed in numerous transitions at 1, 2, and 3 mm, acquired in a spectral-line survey of Sgr B2(N), conducted with the telescopes of the Arizona Radio Observatory (ARO). Between 22 and 54 individual, unblended lines for the 12 C species and 2-54 for 13 C-substituted analogs were modeled in a global radiative transfer analysis. All five molecules were found to consistently exhibit two velocity components near V LSR ∼ 64 and 73 km s −1 , with column densities ranging from N tot ∼ 3 × 10 14 −4 × 10 17 cm −2 and ∼2 × 10 13 −1 × 10 17 cm −2 for the 12 C and 13 C species, respectively. Based on 14 different isotopic combinations, ratios were obtained in the range 12 C/ 13 C = 15±5 to 33±13, with an average value of 24±7, based on comparison of column densities. These measurements better anchor the 12 C/ 13 C ratio at the Galactic center, and suggest a slightly revised isotope gradient of 12 C/ 13 C = 5.21(0.52) D GC + 22.6(3.3). As indicated by the column densities, no preferential 13 C enrichment was found on the differing carbon sites of CH 3 CCH, CH 2 CHCN, and CH 3 CH 2 CN. Because of the elevated temperatures in Sgr B2(N), 13 C isotopic substitution is effectively "scrambled," diminishing chemical fractionation effects. The resulting ratios thus reflect stellar nucleosynthesis and Galactic chemical evolution, as is likely the case for most warm clouds.

show abstract

PRECISE OBSERVATIONS OF THE ¹²C/¹³C RATIOS OF HC₃N IN THE LOW-MASS STAR-FORMING REGION L1527

Cited by 27 publications

References 56 publications

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Deep K-band Observations of TMC-1 with the Green Bank Telescope: Detection of HC₇O, Nondetection of HC₁₁N, and a Search for New Organic Molecules

The ¹²C/¹³C Ratio in Sgr B2(N): Constraints for Galactic Chemical Evolution and Isotopic Chemistry

Contact Info

Product

Resources

About

PRECISE OBSERVATIONS OF THE 12C/13C RATIOS OF HC3N IN THE LOW-MASS STAR-FORMING REGION L1527

Cited by 27 publications

References 56 publications

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Cyanoacetylene in the outflow/hot molecular core G331.512−0.103

Deep K-band Observations of TMC-1 with the Green Bank Telescope: Detection of HC7O, Nondetection of HC11N, and a Search for New Organic Molecules

The 12C/13C Ratio in Sgr B2(N): Constraints for Galactic Chemical Evolution and Isotopic Chemistry

Contact Info

Product

Resources

About

PRECISE OBSERVATIONS OF THE ¹²C/¹³C RATIOS OF HC₃N IN THE LOW-MASS STAR-FORMING REGION L1527

Deep K-band Observations of TMC-1 with the Green Bank Telescope: Detection of HC₇O, Nondetection of HC₁₁N, and a Search for New Organic Molecules

The ¹²C/¹³C Ratio in Sgr B2(N): Constraints for Galactic Chemical Evolution and Isotopic Chemistry