The Detection of Extragalactic [TSUP]15[/TSUP]N: Consequences for NitrogenNucleosynthesis and Chemical Evolution

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

doi:10.1086/311875

Cited by 61 publications

(66 citation statements)

References 25 publications

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“…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 Ratiossupporting

confidence: 64%

“…C01 detected the HCN J = 1−0 and 3-2 transitions, while Chin et al (1999) reported the detection of the J = 1−0 lines of HCN, H 13 CN, and HC 15 N, indicating a surprisingly small 14 N/ 15 N isotope ratio. Here we combine the three J = 1−0 transitions with detections of the HCN and H 13 CN J = 3−2 lines and a highly tentative detection of the HCN J = 4−3 transition (Fig.…”

Section: Hcnmentioning

confidence: 99%

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Dense gas in nearby galaxies

Wang

Henkel²,

Chin

et al. 2004

A&A

129

184

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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.

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Section: Isotope Ratiossupporting

confidence: 64%

Section: Hcnmentioning

confidence: 99%

Dense gas in nearby galaxies

Wang

Henkel²,

Chin

et al. 2004

A&A

129

184

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“…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

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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.

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“…In the ISM, 15 N/ 14 N ratios from $0.005 to $0.0015 were observed (see Terzieva & Herbst 2000). The molecule HC 15 N was identified in the LMC and in the starburst galaxy NGC 4945, and a 15 N/ 14 N ratio of 1 Â 10 À2 was derived by Chin et al (1999). Thus, we have f 15 N= 14 Ng LMC ¼ 4:3.…”

Section: Other Minor Isotopesmentioning

confidence: 85%

“…This implies that the large difference between LMC and PSC is caused by an underabundance of 14 N in the LMC (relative to the PSC) rather than an overabundance of 15 N. In the future, these observations in the LMC will certainly provide constraints for any theory of Galactic evolution. However, at this time there is considerable uncertainty about a representative abundance in the ISM and about stellar production modes and production sites of 15 N (Gherz et al 1998;Chin et al 1999), so that using the 15 N/ 14 N ratio in dwarf galaxies for testing the validity of our mixing model would be premature. 22 Ne.-Whereas the PSC value 20 Ne/ 22 Ne ¼ 13:7 AE 0:3 is well established from solar wind measurements (Geiss et al 1972;Kallenbach et al 1997), interstellar isotopic data of neon have large error limits, and data from dwarf galaxies are not available.…”

Section: Other Minor Isotopesmentioning

confidence: 99%

Chemical Evolution in Our Galaxy during the Last 5 Gyr

Geiss

Gloeckler

Charbonnel

2002

ApJ

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A significant fraction of the gas in the Galactic disk comes from quasi-continuous infall of external material that is moderately processed by stellar nucleosynthesis. Based on a comparison of the abundances in the protosolar cloud (PSC) and the Local Interstellar Cloud (LIC), we propose that the infalling matter carries the nucleosynthetic signature of dwarf galaxies. The dwarfs have low metallicity, and secondary products of stellar nucleosynthesis are scarce as compared to primary products. Using a simple model, we show that the differences found in the LIC and PSC compositions can be explained by adding material processed in dwarf galaxies to the material processed in the Galactic disk. Moreover, some previously unexplained composition observations in the Galaxy, such as the apparently anomalously high metallicity of the Sun, or the '' 18 O puzzle '' could be resolved in this way.

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The Detection of Extragalactic [TSUP]15[/TSUP]N: Consequences for NitrogenNucleosynthesis and Chemical Evolution

Cited by 61 publications

References 25 publications

Dense gas in nearby galaxies

Dense gas in nearby galaxies

A 1.3 cm line survey toward Orion KL

Chemical Evolution in Our Galaxy during the Last 5 Gyr

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