A Search for Evidences of Small-Scale Imhomogeneities in Dense Cores from Line Profile Analysis

TL;DR

This study searches for small-scale inhomogeneities in dense star-forming cores by analyzing line profile fluctuations in HCN and HCO+ emissions, revealing numerous thermal fragments indicative of complex internal structures.

Contribution

It introduces a method to detect and quantify small-scale inhomogeneities in dense cores using line profile analysis and Fourier filtering, providing new insights into their internal structure.

Findings

Detected line temperature fluctuations exceeding noise levels.

Estimated millions of small thermal fragments within the cores.

Modeled physical parameters of fragments in S140.

Abstract

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-time observations of the S140 and S199 high-mass star-forming cores were carried out. The data were processed by the Fourier filtering method. Line temperature fluctuations that exceed noise level were detected. Assuming the cores consist of a large number of randomly moving small thermal fragments a total number of fragments is $\sim 4\cdot 10^6$ for the region with linear size $\sim 0.1$~pc in S140 and $\sim 10^6$ for the region with linear size $\sim 0.3$~pc in S199. Physical parameters of fragments in S140 were obtained from detailed modeling of the HCN emission in a framework of the clumpy cloud model.