1998ApJ...507L.171W

We present 100 and 200 µm ISOPHOT observations of the dense core L1498. We have mapped the central core by using ΔI₂₀₀=I₂₀₀-I₁₀₀MΘ, where ΔI₂₀₀ is a measure of the emission from the cold dust and Θ=I₁₀₀MI₂₀₀ in the outer regions. The dust continuum emission provides information about the chemical depletion and the properties of cold cores where there is a lack of gas tracers. Previous observations of L1498 show that the emission from CS and CCS lies outside of the NH₃ core. The peak in ΔI₂₀₀ lies close to the previously observed NH₃ peak. A comparison with high spatial resolution observations of C¹⁸O emission shows that the ΔI₂₀₀ maximum coincides with a dip in the C¹⁸O emission at the core center. We estimate that the depletion factor for C¹⁸O in this region is at least 8 and is likely to be much larger. Such high depletion has significant implications for studies of gas-grain chemistry and protostellar cores.