Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

Assuming the CH₃OH column densities given by Meier et al. (2005) these intensity ratios translate into SiO-CH₃OH column density ratios of ${\sim}0.01{-}0.04$ for $n\gtrsim5\times10^4$ cm^-3 ( ${\sim}3$ times larger if $n\sim10^4$ cm^-3).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... ${\sim}0.01{-}0.03$ )

Calculated from SiO and C₂H₅OH column densities measured in GC clouds (Martín-Pintado et al. 1997,2001), assuming a constant C₂H₅OH-to-CH₃OH abundance ratio of ${\sim}0.05$ (Requena-Torres et al. 2005, in prep.).

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.