First results from the UHRF: ultra-high-resolution observations of interstellar CH, Formula and CN towards Formula Ophiuchi

Crawford, Ian; Barlow, M. J.; Diego, F.; Spyromilio, J.

doi:10.1093/mnras/266.4.903

Cited by 28 publications

(32 citation statements)

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“…Ca has a similar condensation temperature to Ti and therefore comes out of the solid state to produce Ca  in similar energetic/shocked regions to where Ti  is observed, but will be ionised to Ca  in more diffuse, strongly irradiated clouds, so it tends to be found in greatest abundances in warm yet moderately well-shielded regions. CH + is photodissociated in less dense regions, but has been shown to have a broader velocity distribution than K  (Pan et al 2005), consistent with the formation of this molecule in warmer haloes surrounding cold cloud cores (Crawford et al 1994). K  is a good tracer for cool, quiescent, well-shielded clouds with low thermal broadening where the radiation field is attenuated and the photoionisation rate is relatively low.…”

Section: Comparing the Hypothetical Ch 2 Cnmentioning

confidence: 58%

The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

Cordiner

Sarre²

2007

A&A

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The hypothesis that the cyanomethyl anion CH 2 CN − is responsible for the relatively narrow diffuse interstellar band (DIB) at 8037.8± 0.15 Å is examined with reference to new observational data. The 0 0 0 absorption band arising from the 1 B 1 −X 1 A transition from the electronic ground state to the first dipole-bound state of the anion is calculated for a rotational temperature of 2.7 K using literature spectroscopic parameters and results in a rotational contour with a peak wavelength of 8037.78 Å. By comparison with diffuse band and atomic line absorption spectra of eight heavily-reddened Galactic sightlines, CH 2 CN − is found to be a plausible carrier of the λ8037 diffuse interstellar band provided the rotational contour is Doppler-broadened with a b parameter between 16 and 33 km s The rotational level populations may be influenced by nuclear spin statistics, resulting in the appearance of additional transitions from K a = 1 of ortho CH 2 CN − near 8025 and 8050 Å that are not seen in currently available interstellar spectra. For CH 2 CN − to be the carrier of the λ8037 diffuse interstellar band, either a) there must be mechanisms that convert CH 2 CN − from the ortho to the para form, or b) the chemistry that forms CH 2 CN − must result in a population of K a levels approaching a Boltzmann distribution near 3 K.

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Section: Comparing the Hypothetical Ch 2 Cnmentioning

confidence: 58%

The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

Cordiner

Sarre²

2007

A&A

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“…The velocity structure of CH in this line of sight is somewhat complex but gives an FWHM of approximately 2 km s~1 for a single "-doublet component, from the work of Crawford et al (1994). This translates to 0.5 cm~1 near 1370…”

Section: Line Widthsmentioning

confidence: 93%

Assignment of the λ1369.13 Diffuse Interstellar Absorption Band and Three Other Far‐Ultraviolet Interstellar Absorption Lines to the CH Molecule

Watson

2001

ApJ

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The three unidentiÐed interstellar lines jj1368. 74, 1369.13, and 1370.87 are here assigned to the CH molecule, including the di †use interstellar band (DIB) at 1369.13 A consistent rotational assignment A . of the interstellar lines and the 3dÈX 2% laboratory spectrum is presented. The predominant broadening mechanism of the lines appears to be predissociation, which is found to be greater for lines with upper levels of d parity, including the DIB, than for lines with upper levels of c parity. The oscillator strength of the 3dÈX 2% transition is estimated to be f B 0.033. Using the theoretical n* dependence of the parameters together with the wavenumber of the observed laboratory Q-form branch, an unidentiÐed interstellar line at 1270.96 is assigned to the strongest line of the 4dÈX 2% transition of CH.A Subject headings : ISM : lines and bands È ISM : molecules È methods : laboratory È molecular data È ultraviolet : ISM

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“…Since we cannot separate the uncertainty in the baseline definition, we adopt the smallest number of Gaussians consistent with the dataset (with reduced χ 2 close to 1). We chose 3 Gaussians rather than 2 because Crawford et al (1994) report a 3-Gaussians decomposition of the ultra-high resolution CH + profile toward ζOph. The final value from the UVES data is thus R = 78.47 ± 2.65(3.53), with a 3-Gaussian fit.…”

Section: ζ Ophmentioning

confidence: 99%

Interstellar $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratios through CH$^+\lambda\lambda $3957,4232 absorption in local clouds: incomplete mixing in the ISM

Casassus¹,

Stahl²,

Wilson

2005

A&A

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Abstract.The 12 C/ 13 C isotope ratio is a tracer of stellar yields and the efficiency of mixing in the ISM. 12 CH + / 13 CH + is not affected by interstellar chemistry, and is the most secure way of measuring 12 C/ 13 C in the diffuse ISM. R = 12 C/ 13 C is 90 in the solar system. Previous measurements of 12 CH + λλ3957.7,4232.3 and 13 CH + λλ3958.2,4232.0 absorption toward nearby stars indicate some variations in 12 C/ 13 C, with values ranging from 40 to 90 suggesting inefficient mixing. Except for the cloud toward ζOph, these R values are strongly affected by noise. With UVES on the VLT we have improved on the previous interstellar 12 C/ 13 C measurements. The weighted 12 C/ 13 C ratio in the local ISM is 78.27 ± 1.83, while the weighted dispersion of our measurements is 12.7, giving a 6.9σ scatter. Thus we report on a 6.9σ detection of 16.2% root-mean-square variations in the carbon isotopic ratio on scales of ∼100 pc: R = 74.7 ± 2.3 in the ζOph cloud, while R = 88.6 ± 3.0 toward HD 152235 in the Lupus clouds, R = 62.2 ± 5.3 towards HD 110432 in the Coalsack, and R = 98.9 ± 10.1 toward HD 170740. The observed variations in 13 C/ 12 C are the first significant detection of chemical heterogeneity in the local ISM.

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First results from the UHRF: ultra-high-resolution observations of interstellar CH, Formula and CN towards Formula Ophiuchi

Cited by 28 publications

References 0 publications

The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

Assignment of the λ1369.13 Diffuse Interstellar Absorption Band and Three Other Far‐Ultraviolet Interstellar Absorption Lines to the CH Molecule

Interstellar $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratios through CH$^+\lambda\lambda $3957,4232 absorption in local clouds: incomplete mixing in the ISM

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First results from the UHRF: ultra-high-resolution observations of interstellar CH, Formula and CN towards Formula Ophiuchi

Cited by 28 publications

References 0 publications

The CH$_\mathsf{2}$CN- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

The CH$_\mathsf{2}$CN- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

Assignment of the λ1369.13 Diffuse Interstellar Absorption Band and Three Other Far‐Ultraviolet Interstellar Absorption Lines to the CH Molecule

Interstellar $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratios through CH$^+\lambda\lambda $3957,4232 absorption in local clouds: incomplete mixing in the ISM

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The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?

The CH$_\mathsf{2}$CN^- molecule: carrier of the $\mathsf{\lambda}$8037 diffuse interstellar band?