The millimeter and submillimeter spectrum of CN in its first four vibrational states

Skatrud, David D.; Lucia, Frank C. De; Blake, Geoffrey A.; Sastry, K. V. L. N.

doi:10.1016/0022-2852(83)90290-4

Cited by 70 publications

(43 citation statements)

References 12 publications

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“…With an observed line intensity ratio of 1.58 ± 0.06 (Table 2) and τ 1 = 2τ 2 (see Skatrud et al 1983 for relative LTE intensities under optically thin conditions) we then find…”

Section: The [Cn]/[ 13 Cn] Abundance Ratiomentioning

confidence: 57%

“…For the fit to the line profile we assumed optical depth ratios between individual HF components that are consistent with the relative intensities given by Skatrud et al (1983). Observed CN profiles are displayed in Fig.…”

Section: Cn Line Intensity Anomaliesmentioning

confidence: 93%

“…where Σg i,1 and Σg i,2 are 0.667 and 0.333, respectively (Skatrud et al 1983), we then obtain for the "optical depth corrected" total CN N = 1−0 line intensities I 1 = I 2 = 60.4±5.4 K km s −1 . For 13 CN (spectra are shown in Fig.…”

Section: The [Cn]/[ 13 Cn] Abundance Ratiomentioning

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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“…With an observed line intensity ratio of 1.58 ± 0.06 (Table 2) and τ 1 = 2τ 2 (see Skatrud et al 1983 for relative LTE intensities under optically thin conditions) we then find…”

Section: The [Cn]/[ 13 Cn] Abundance Ratiomentioning

confidence: 57%

Section: Cn Line Intensity Anomaliesmentioning

confidence: 93%

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Dense gas in nearby galaxies

Wang

Henkel²,

Chin

et al. 2004

A&A

129

184

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“…This work has been been partially supported by the EC Marie-Curie Research Training Network "The Molecular Universe" (MRTN-CT-2004-512302). Skatrud et al (1983). …”

Section: Discussionmentioning

confidence: 99%

Nitrogen chemistry and depletion in starless cores

Hily-Blant¹,

Walmsley

Forêts

et al. 2010

A&A

119

128

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Aims. We investigated the chemistry of nitrogen-containing species, principally isotopologues of CN, HCN, and HNC, in a sample of pre-protostellar cores. Methods. We used the IRAM 30 m telescope to measure the emission in rotational and hyperfine transitions of CN, HCN, 13 CN, H 13 CN, HN 13 C, and HC 15 N in L 1544, L 183, Oph D, L 1517B, L 310. The observations were made along axial cuts through the dust emission peak, at a number of regularly-spaced offset positions. The observations were reduced and analyzed to obtain the column densities, using the measurements of the less abundant isotopic variants in order to minimize the consequences of finite optical depths in the lines. The observations were compared with the predictions of a free-fall gravitational collapse model, which incorporates a non-equilibrium treatment of the relevant chemistry. Results. We found that CN, HCN, and HNC remain present in the gas phase at densities well above that at which CO depletes on to grains. The CN:HCN and the HNC:HCN abundance ratios are larger than unity in all the objects of our sample. Furthermore, there is no observational evidence for large variations of these ratios with increasing offset from the dust emission peak and hence with density. Whilst the differential freeze-out of CN and CO can be understood in terms of the current chemistry, the behaviour of the CN:HCN ratio is more difficult to explain. Models suggest that most nitrogen is not in the gas phase but may be locked in ices. Unambiguous conclusions require measurements of the rate coefficients of the key neutral-neutral reactions at low temperatures.

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“…To derive line intensities, we fitted simple Gaussian profiles to the observed lines taking Notes. CN N = 2-1 line frequencies were measured in laboratory by Skatrud et al (1983); we use here the fitted values from the CDMS Database (Müller et al 2001). into account the hyperfine structure of the C 17 O J = 2−1 and CN N = 2−1 lines. We used the "HFS (hyperfine structure)" method of the CLASS data analysis program in the GILDAS 1 package for this purpose.…”

Section: Observationsmentioning

confidence: 99%

A sensitive survey for¹³CO, CN, H₂CO, and SO in the disks of T Tauri and Herbig Ae stars

Guilloteau¹,

Folco²,

Dutrey³

et al. 2013

A&A

106

151

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Aims. We investigate the suitability of several molecular tracers, in particular CN N = 2−1 line emission, as a confusion-free probe of the kinematics of circumstellar disks. Methods. We use the IRAM 30-m telescope to perform a sensitive search for CN N = 2−1 in 42 T Tauri or Herbig Ae systems located principally in the Taurus-Auriga region. 13 CO J = 2−1 is observed simultaneously to provide an indication of the level of confusion with the surrounding molecular cloud. The bandpass also contains two transitions of ortho-H 2 CO, one of SO and the C 17 O J = 2−1 line which provide complementary information on the nature of the emission. Results. While 13 CO is in general dominated by residual emission from the cloud, CN exhibits a high disk detection rate >50% in our sample. We even report CN detection in stars for which interferometric searches failed to detect 12 CO, presumably because of obscuration by a foreground, optically thick, cloud. Comparison between CN and o-H 2 CO or SO line profiles and intensities divide the sample in two main categories. Sources with SO emission are bright and have strong H 2 CO emission, leading in general to [H 2 CO/CN] > 0.5. Furthermore, their line profiles, combined with a priori information on the objects, suggest that the emission is coming from outflows or envelopes rather than from a circumstellar disk. On the other hand, most sources have [H 2 CO/CN] < 0.3, no SO emission, and some of them exhibit clear double-peaked profiles characteristics of rotating disks. In this second category, CN is likely tracing the proto-planetary disks. From the line flux and opacity derived from the hyperfine ratios, we constrain the outer radii of the disks, which range from 300 to 600 AU. The overall gas disk detection rate (including all molecular tracers) is ∼68%, and decreases for fainter continuum sources. Conclusions. The current study demonstrates that gas disks, like dust disks, are ubiquitous around young PMS stars in regions of isolated star formation, and that a large fraction of them have R out > ∼ 300 AU. It also shows the potential of the CN N = 2−1 transition to probe the kinematics of these disks, thereby measuring the stellar mass, using high resolution observations with ALMA.

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The millimeter and submillimeter spectrum of CN in its first four vibrational states

Cited by 70 publications

References 12 publications

Dense gas in nearby galaxies

Dense gas in nearby galaxies

Nitrogen chemistry and depletion in starless cores

A sensitive survey for¹³CO, CN, H₂CO, and SO in the disks of T Tauri and Herbig Ae stars

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The millimeter and submillimeter spectrum of CN in its first four vibrational states

Cited by 70 publications

References 12 publications

Dense gas in nearby galaxies

Dense gas in nearby galaxies

Nitrogen chemistry and depletion in starless cores

A sensitive survey for13CO, CN, H2CO, and SO in the disks of T Tauri and Herbig Ae stars

Contact Info

Product

Resources

About

A sensitive survey for¹³CO, CN, H₂CO, and SO in the disks of T Tauri and Herbig Ae stars