A search for evidence of small-scale inhomogeneities in dense cores from line profile analysis

In order to search for intensity fluctuations on the HCN(1-0) and HCO⁺(1-0) line profiles, which could arise due to possible small-scale inhomogeneous structure, long-term observations of high-mass star-forming cores S140 and S199 were carried out. The data were processed by the Fourier filtering method. Line temperature fluctuations that exceed the noise level were detected. Assuming the cores consist of a large number of randomly moving small thermal fragments, the total number of fragments is ∼ 4 × 10⁶ for the region with linear size ∼ 0.1 pc in S140 and ∼ 10⁶ for the region with linear size ∼ 0.3 pc in S199. Physical parameters of fragments in S140 were obtained from detailed modeling of the HCN emission in the framework of the clumpy cloud model.