1995A&A...301..941H

We report the discovery of the SO (N_J=1₀-0₁) line near 30GHz with the MPIfR 100m telescope in two dense cores located in the galactic cirrus clouds MCLD 123.5+24.9 and MCLD 126.6+24.5. The emission is quite intense and extends over several arcmin. Since the SO (N_J=1₀-0₁) line is most likely optically thick, we can only derive a lower limit for the cloud averaged column densities N(SO)>10¹³cm^–2. Both cores have also been mapped in the ¹³CO (J=3-2) transition using the KOSMA 3-m telescope. Applying an escape propability model to match the observed line strength of this transition and of already published (J=1-0) data gives column densities in the range 2.0x10¹⁵cm^–2=<N(¹³CO)=<6.0x10¹⁵cm^–2 and volume densities in the range of 0.5x10⁴cm^–3=<n(H₂)=<2.5x10⁴cm^–3. Comparison of the SO column densities with the H₂ column densities derived from these ¹³CO or already published C¹⁸O column densities gives a lower limit for the fractional abundance of X(SO)>4x10^–9.