Cyanogen excitation in diffuse interstellar clouds

Katherine C. Rot*, David M. Meyer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


We present high signal-to-noise ratio observations of optical CN absorption from die B 2Σ+-X 2Σ+ (0, 0) and (1, 0) vibrational bands in the five diffuse lines of sight toward ζ Ophiuchi, ζ Persei, HD 27778, HD 21483, and HD 154368. The observed level of CN excitation is consistent with direct satellite and rocket measurements of the cosmic microwave background radiation (CMBR), implying that local collisional effects are small. The weak 2.64 mm CN line emission observed toward HD 21483 and HD 154368 is used to correct the observed CN excitation temperatures and derive a weighted mean CMBR temperature at 2.64 mm of 2.729(+0.023, -0.031) K which agrees remarkably well with the COBE measurement obtained with the FIRAS instrument of 2.726 ± 0.010 K. These absorption data were obtained during 10 separate observing runs, and we find excellent agreement between independent equivalent width measurements resulting from widely varying instrument combinations. Finally we discuss the limitations and future applications of CN excitation absorption-line measurements.

Original languageEnglish (US)
Pages (from-to)129-143
Number of pages15
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 1 1995


  • Cosmic microwave background
  • ISM: clouds
  • ISM: molecules

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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