CN and HCN in dense interstellar clouds

Gai I. Boger*, Amiel Sternberg

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


We present a theoretical investigation of CN and HCN molecule formation in dense interstellar clouds. We study the gas-phase CN and HCN production efficiencies from the outer photon-dominated regions (PDRs) into the opaque cosmic-ray-dominated cores. We calculate the equilibrium densities of CN and HCN and of the associated species C+, C, and CO, as functions of the far-ultraviolet (FUV) optical depth. We consider isothermal gas at 50 K, with hydrogen particle densities from 102 to 106 cm -3. We study clouds that are exposed to FUV fields with intensities (at 1000 Å) from 1 × 10-18 to 1 × 10-14 ergs s-1 cm-2 Hz-1 sr-1, or 20 to 2 × 105 times the mean interstellar FUV intensity. We assume cosmic-ray H2 ionization rates ranging from 5 × 10 -17 s-1 to an enhanced value of 5 × 10-16 s-1. We also examine the sensitivity of the density profiles to the gas-phase sulfur abundance.

Original languageEnglish
Pages (from-to)302-315
Number of pages14
JournalAstrophysical Journal
Issue number1 I
StatePublished - 10 Oct 2005


  • Galaxies: ISM
  • ISM: evolution
  • Molecular processes


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