Early-type stars observed in the ESO UVES Paranal observatory project - IV. studies of CN, CH+ and CH in the interstellar medium

J. Smoker*, C. Ledoux, E. Jehin, F. P. Keenan, M. Kennedy, R. Cabanac, C. Melo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


High spectral resolution (~80 000) and signal-to-noise observations from the Ultraviolet and Visual Echelle Spectrograph Paranal Observatory Project (UVES-POP) are used to study the interstellarmolecular lines CN (3874 Å), CH+ (3957, 4232 Å) and CH (3886, 4300 Å) towards 74 O- and B-type stellar sightlines. Additionally, archive data are presented for 140 ELODIE early-type stellar sightlines at R = 42 000, plus 25 FEROS at R = 48 000 and 3 UVES at R > 50 000, mainly in the CH+ (4232 Å) and CH (3886, 4300 Å) transitions. Detection rates are ~45 per cent for CN and ~67 per cent for the other lines in the POP sample, and ~10-15 per cent for CH+ and CH lines in the additional sample. CH and CH+ are well correlated between log[N(CH) cm-2]~12-14, implying that these clouds are CH+-like CH and not CN-like CH. CH is also very well correlated with Na I D in the range log[N(Na I cm-2]) ~12.2-14.2. A few sightlines show tentative velocity shifts of ~2 km s-1 between CH and CH+, which appear to be caused by differences in component strength in blends, and hence do not provide firm evidence for shocks. Finally, we describe a search for 13CH+ in a sightline towards HD 76341. No 13CH+ is detected, placing a limit on the 13CH+ to 12CH+ ratio of ~0.01. If a formal fit is attempted, the equivalent width ratio in the two isotopes is a factor ~90 but with large errors. 

Original languageEnglish
Pages (from-to)1127-1136
JournalMonthly Notices of the Royal Astronomical Society
Early online date20 Dec 2013
Publication statusPublished - 21 Feb 2014


  • Abundances-ISM
  • Clouds-ISM
  • Early-type-ISM
  • General-ISM
  • Stars
  • Structure

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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