Interstellar CNO isotope Ratios

Henkel, C.; Wilson, T. L.; Langer, N.; Chin, Y.-N.; Mauersberger, R.

doi:10.1007/3540586210_5

Cited by 33 publications

(48 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been reported that the galactic ratio appears to be dependent on the distance from the galactic centre (see e.g., Henkel et al 1994;Wilson & Rood 1994). The interstellar ratios estimated within 100 pc along different lines of sight vary between 62 and 98 (Casassus et al 2005).…”

Section: The Relative Abundances C and O Isotopesmentioning

confidence: 94%

OH/IR stars and their superwinds as observed by theHerschelSpace Observatory

Justtanont

Teyssier

Barlow

et al. 2013

A&A

View full text Add to dashboard Cite

Aims. In order to study the history of mass loss in extreme OH/IR stars, we observed a number of these objects using CO as a tracer of the density and temperature structure of their circumstellar envelopes. Methods. Combining CO observations from the Herschel Space Observatory with those from the ground, we trace mass loss rates as a function of radius in five extreme OH/IR stars. Using radiative transfer modelling, we modelled the dusty envelope as well as the CO emission. The high-rotational transitions of CO indicate that they originate in a dense superwind region close to the star while the lower transitions tend to come from a more tenuous outer wind which is a result of the mass loss since the early AGB phase.Results. The models of the circumstellar envelopes around these stars suggest that they have entered a superwind phase in the past 200-500 years. The low 18 O/ 17 O (∼0.1 compared to the solar abundance ratio of ∼5) and 12 C/ 13 C (3-30 cf. the solar value of 89) ratios derived from our study support the idea that these objects have undergone hot-bottom burning and hence that they are massive M ≥ 5 M AGB stars.

show abstract

Section: The Relative Abundances C and O Isotopesmentioning

confidence: 94%

OH/IR stars and their superwinds as observed by theHerschelSpace Observatory

Justtanont

Teyssier

Barlow

et al. 2013

A&A

View full text Add to dashboard Cite

show abstract

“…As a consequence, τ( 13 CO J = 2−1)> τ( 13 CO J = 1−0). The fact that the correlation between 12 C/ 13 C and 16 O/ 18 O ratios is almost independent of the choice of transition (J = 1−0 or J = 2−1) does not prove but strongly suggests that the 13 CO opacities are small (see also Bergman et al 1992 and H94 Henkel et al 1994b;Langer & Henkel 1995 Table 2) and a 12 C/ 13 C ratio of 50 ± 10 we obtain 14 N/ 15 N = 105 ± 26, in good agreement with Chin et al (1999).…”

Section: Isotope Ratiosmentioning

confidence: 99%

Dense gas in nearby galaxies

Wang

Henkel²,

Chin

et al. 2004

A&A

Self Cite

129

184

View full text Add to dashboard Cite

Abstract.A multi-line millimeter-wave study of the nearby starburst galaxy NGC 4945 has been carried out using the Swedish-ESO Submillimeter Telescope (SEST). The study covers the frequency range from 82 GHz to 354 GHz and includes 80 transitions of 19 molecules. 1.3 mm continuum data of the nuclear source are also presented. An analysis of CO and 1.3 mm continuum fluxes indicates that the conversion factor between H 2 column density and CO J = 1−0 integrated intensity is smaller than in the galactic disk by factors of 5−10. A large number of molecular species indicate the presence of a prominent high density interstellar gas component characterized by n H 2 ∼ 10 5 cm −3 . Some spectra show Gaussian profiles. Others exhibit two main velocity components, one at ∼450 km s −1 , the other at ∼710 km s −1 . While the gas in the former component has a higher linewidth, the latter component arises from gas that is more highly excited as is indicated by HCN, HCO + and CN spectra. Abundances of molecular species are calculated and compared with abundances observed toward the starburst galaxies NGC 253 and M 82 and galactic sources. Apparent is an "overabundance" of HNC in the nuclear environment of NGC 4945. While the HNC/HCN J = 1−0 line intensity ratio is ∼0.5, the HNC/HCN abundance ratio is ∼1. From a comparison of K a = 0 and 1 HNCO line intensities, an upper limit to the background radiation of 30 K is derived. While HCN is subthermally excited (T ex ∼ 8 K), CN is even less excited (T ex ∼ 3−4 K), indicating that it arises from a less dense gas component and that its N = 2−1 line can be optically thin even though its N = 1−0 emission is moderately optically thick. Overall, fractional abundances of NGC 4945 suggest that the starburst has reached a stage of evolution that is intermediate between those observed in NGC 253 and M 82. Carbon, nitrogen, oxygen and sulfur isotope ratios are also determined. Within the limits of uncertainty, carbon and oxygen isotope ratios appear to be the same in the nuclear regions of NGC 4945 and NGC 253. S ratios (6.4 ± 0.3, 195 ± 45, 105 ± 25 and 13.5 ± 2.5 in NGC 4945, respectively) appear to be characteristic properties of a starburst environment in which massive stars have had sufficient time to affect the isotopic composition of the surrounding interstellar medium.

show abstract

“…Thus, isotope selective photodissociation by UV photons should not affect the 14 N/ 15 N ratio a lot either. Since 15 N may originate in massive stars and is potentially destroyed in lower mass stars (e.g., Henkel et al 1994;Wilson & Rood 1994;Chin et al 1999;Wang et al 2009), such an enhanced 15 N in a massive starforming regions like Orion KL can be expected. Furthermore, our value is similar to the 111 ± 17 in the Large Magellanic Cloud (LMC) massive star-forming region N113, the ∼100 in the LMC star-forming region N159HW, and the value in the central region of NGC 4945 (Chin et al 1999).…”

Section: 23mentioning

confidence: 99%

A 1.3 cm line survey toward Orion KL

Gong

Henkel

Thorwirth

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

Context. The nearby Orion Kleinmann-Low nebula is one of the most prolific sources of molecular line emission. It has served as a benchmark for spectral line searches throughout the (sub)millimeter regime. Aims. The main goal is to systematically study the spectral characteristics of Orion KL in the λ ∼ 1.3 cm band. Methods. We carried out a spectral line survey with the Effelsberg-100 m telescope toward Orion KL. It covers the frequency range between 17.9 GHz and 26.2 GHz, i.e., the radio "K band". We also examined ALMA maps to address the spatial origin of molecules detected by our 1.3 cm line survey. Results. In Orion KL, we find 261 spectral lines, yielding an average line density of about 32 spectral features per GHz above 3σ (a typical value of 3σ is 15 mJy). The identified lines include 164 radio recombination lines (RRLs) and 97 molecular lines. The RRLs, from hydrogen, helium, and carbon, stem from the ionized material of the Orion Nebula, part of which is covered by our beam. The molecular lines are assigned to 13 different molecular species including rare isotopologues. A total of 23 molecular transitions from species known to exist in Orion KL are detected for the first time in the interstellar medium. Non-metastable (J > K) 15 NH 3 transitions are detected in Orion KL for the first time. Based on the velocity information of detected lines and the ALMA images, the spatial origins of molecular emission are constrained and discussed. A narrow feature is found in SO 2 (8 1,7 −7 2,6 ), but not in other SO 2 transitions, possibly suggesting the presence of a maser line. Column densities and fractional abundances relative to H 2 are estimated for 12 molecules with local thermodynamic equilibrium (LTE) methods. Rotational diagrams of non-metastable 14 NH 3 transitions with J = K + 1 to J = K + 4 yield different results; metastable (J = K) 15 NH 3 is found to have a higher excitation temperature than non-metastable 15 NH 3 , also indicating that they may trace different regions. Elemental and isotopic abundance ratios are also estimated: He/H = (8.7 ± 0.7)% derived from the ratios between helium RRLs and hydrogen RRLs; 12 C/ 13 C = 63 ± 17 from 12 CH 3 OH/ 13 CH 3 OH; 14 N/ 15 N =100 ± 51 from 14 NH 3 / 15 NH 3 ; and D/H = (8.3 ± 4.5) × 10 −3 from NH 2 D/NH 3 . The dispersion of the He/H ratios derived from Hα/Heα pairs to Hδ/Heδ pairs is very small, which is consistent with theoretical predictions that the departure coefficients b n factors for hydrogen and helium are nearly identical. Based on a non-LTE code that neglects excitation by the infrared radiation field and a likelihood analysis, we find that the denser regions have lower kinetic temperature, which favors an external heating of the hot core.

show abstract

Interstellar CNO isotope Ratios

Cited by 33 publications

References 41 publications

OH/IR stars and their superwinds as observed by theHerschelSpace Observatory

OH/IR stars and their superwinds as observed by theHerschelSpace Observatory

Dense gas in nearby galaxies

A 1.3 cm line survey toward Orion KL

Contact Info

Product

Resources

About