A Very High Resolution Survey of Interstellar CH and CH +

Crane, P.; Lambert, David L.; Sheffer, Yaron

doi:10.1086/192180

Cited by 101 publications

(142 citation statements)

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“…Thus, in principle we expect much less variation due to structure in the foreground IS gas towards ζ Per and absorption lines seen in the spectra of that star should be a good indication of the instrumental stability and homogeneity of our measurements. Data from the literature (Allen 1994;Crane et al 1995) do show that W λ values for CH, CH + , CN, Ca i, and Ca ii are constant within errors for ζ Per.…”

Section: Description Of Optical Observationsmentioning

confidence: 87%

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

Boissé¹,

Rollinde

Hily-Blant

et al. 2009

A&A

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Context. The runaway star HD 34078, initially selected to investigate small scale structure in a foreground diffuse cloud, has been shown to be surrounded by highly excited H 2 , the origin of which is unclear. Aims. We first search for an association between the foreground cloud and HD 34078. Second, we extend previous investigations of temporal absorption line variations (CH, CH + , H 2 ) in order to better characterize them and understand their relation to small-scale structure in the molecular gas. Methods. We have mapped the 12 CO(2-1) emission at 12 resolution around HD 34078's position, using the 30 m IRAM antenna. The follow-up of CH and CH + absorption lines has been extended over 5 more years: 26 visible spectra have been acquired since 2003 at high or intermediate resolution. In parallel, CH absorption towards the reddened star ζ Per has been monitored to check the instrumental stability and homogeneity of our measurements. Three more FUSE spectra have been obtained to search for N(H 2 ) variations. Results. CO observations show a pronounced maximum near HD 34078's position, clearly indicating that the star and diffuse cloud are associated. The optical spectra confirm the reality of strong, rapid and correlated CH and CH + fluctuations (up to 26% for N(CH + ) between 2007 and 2008). On the other hand, N(H 2 , J = 0) has varied by less than 5% over 4 years, indicating the absence of marked density structure at scales below 100 AU. We also discard N(CH) variations towards ζ Per at scales less than 20 AU. Conclusions. Observational constraints from this work and from 24 μm dust emission appear to be consistent with H 2 excitation but inconsistent with steady-state bow shock models and rather suggest that the shell of compressed gas surrounding HD 34078 or lying at the boundary of a small foreground clump is seen at an early stage of the interaction. The CH and CH + time variations as well as their high abundances are likely due to chemical structure in the shocked gas layer located at the stellar wind/ambient cloud interface. Finally, the lack of variation in both N(H 2 , J = 0) towards HD 34078 and N(CH) towards ζ Per suggests that quiescent molecular gas is not subject to pronounced small-scale structure.

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Section: Description Of Optical Observationsmentioning

confidence: 87%

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

Boissé¹,

Rollinde

Hily-Blant

et al. 2009

A&A

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“…With a single 1872-element Reticon linear self-scanned photodiode array and the echelle, the typical high-resolution spectrum covered 15 Â at 5000 Â wavelength and the spectral resolving power could approach R-200,000 with a narrow slit (0.3 arcsec). A number of observing programs have used the echelle in double-pass and a TI 800X800 CCD at resolving power R -500,000 (Lambert et al 1990;Hobbs and Welty 1991;Crane et al 1994). …”

Section: Introductionmentioning

confidence: 99%

The high-resolution cross-dispersed echelle white-pupil spectrometer of the McDonald Observatory 2.7-m telescope

Tull¹,

MacQueen²,

Sneden³

et al. 1995

PASP

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476

415

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ABSTRACT. A new high-resolution cross-dispersed echelle spectrometer has been installed at the coudé focus of the McDonald Observatory 2.7-m telescope. Its primary goal was simultaneously to gather spectra over as much of the spectral range 3400 À to 1 /¿m as practical, at a resolution R=X/AX -60,000 with signal-to-noise ratio of -100 for stars down to magnitude 11, using 1-h exposures. In the instrument as built, two exposures are all that are needed to cover the full range. Featuring a white-pupil design, fused silica prism cross disperser, and folded Schmidt camera with a Tektronix 2048X2048 CCD used at either of two foci, it has been in regularly scheduled operation since 1992 April. Design details and performance are described.

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“…Such data have recently been obtained with the 0.9 m coude feed telescope (J£ « 3 χ 10 5 ) at Kitt Peak National Observatory (KPNO) (Meyer, Hawkins & Wright 1993), the coude spectrograph (fi « 5 χ 10 5 ) on the McDonald Observatory 2.7 m telescope (Crane, Lambert & Sheffer 1995), and the Ultra High Resolution Facility (UHRF) (R « 10 6 ) on the 3.9 m Anglo-Australian Telescope (AAT) (Diego et al 1995). In the case of detectors, the current generation of CCDs has high quantum efficiency (QE > 60%) from 3100 Â in the near-UV to 9000 Â in the near-IR.…”

Section: Capabilitiesmentioning

confidence: 99%

“…The interstellar CH A-X Λ4300, CH+ A-X Λ4232, and CN B-X A3875 lines have now been surveyed at very high resolution toward a number of stars by Crane, Lambert & Sheffer (1995) using the McDonald coude and Crawford (1995) using the AAT UHRF. These studies generally find no velocity differences between the CH and CH + absorption lines in a given sightline which provides a challenge for some shock models of CH + production.…”

Section: Very High Resolution Ch Ch+ and Cn Surveysmentioning

confidence: 99%

Optical and ultraviolet observations of diffuse interstellar clouds

Meyer

1997

Symp. - Int. Astron. Union

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Abstract.Absorption-line studies of diffuse interstellar clouds have recently been invigorated at ultraviolet wavelengths with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope and at optical wavelengths with efficient high resolution spectrographs and CCD detectors. These instruments have made it possible to explore new regimes in determining the atomic and molecular abundances of diffuse clouds and tracing the velocity structure of interstellar lines. In the case of the atomic gas, the abundances of elements as diverse as oxygen and krypton have been accurately measured with GHRS and are consistent with a local ISM whose metallicity is about 2/3 that of the Sun. GHRS has also provided new insight on molecular processes in diffuse clouds through observations of CO, C2, HCl, and vibrationally-excited H2. With velocity resolutions of 0.3 km s -1 now attainable, optical spectra of species like CH, CH+, and CN are beginning to probe the physical characteristics of diffuse clouds in detail. Similar spectra of interstellar Na I toward resolvable binary star systems have recently revealed a rich variety of small-scale structure in the cold diffuse gas.

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A Very High Resolution Survey of Interstellar CH and CH +

Cited by 101 publications

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CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

The high-resolution cross-dispersed echelle white-pupil spectrometer of the McDonald Observatory 2.7-m telescope

Optical and ultraviolet observations of diffuse interstellar clouds

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A Very High Resolution Survey of Interstellar CH and CH +

Cited by 101 publications

References 0 publications

CO emission and variable CH and CH+absorption towards HD 34078: evidence for a nascent bow shock?

CO emission and variable CH and CH+absorption towards HD 34078: evidence for a nascent bow shock?

The high-resolution cross-dispersed echelle white-pupil spectrometer of the McDonald Observatory 2.7-m telescope

Optical and ultraviolet observations of diffuse interstellar clouds

Contact Info

Product

Resources

About

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?