SIMBAD references

The [CI]³P₁-³P₀ 492 GHz fine structure line has been detected in the high-latitude cloud toward HD 210121 using the James Clerk Maxwell Telescope. The measured [CI] line strengths vary between T_MB=0.6-1.6K and appear correlated with the CO J=1-0 emission. The inferred [CI] column densities can be well explained by models with densities n_H∼500-5000cm^–3 and a low incident radiation field, which causes the C⁺, C -> CO transition zone to be shifted to lower A_V values. The derived N(C)/N(CO) ratio is about 3 6, significantly larger than found in dense PDRs. Cooling by [CI] is larger than that by CO in this cloud and may be compatable to that by [CII] within a factor of a few.