Solid CO in the Taurus dark clouds

Abstract

The infrared vibrational feature of solid state CO at 4.67 µm wavelength is detected towards five sources in or behind the dark cloud complex in Taurus. A comparison with millimetre-wave data suggests that a significant fraction (up to 40 per cent) of the CO may be depleted on to grains. The adjacent CN feature at 4.62 µm observed in W33A by Lacy et al. is absent from our spectra, suggesting that the grain mantles in Taurus are unannealed.