CAOSP abstracts, Volume: 53, No.: 1, year: 2023

Author(s): Vasylkivskyi, Y.V.; Stepkin, S.V.; Konovalenko, O.O.
Journal: Contributions of the Astronomical Observatory Skalnaté Pleso, vol. 53, no. 1, p. 17-27.
Date: 02/2023
Title: The low-frequency carbon radio recombination lines in medium toward S140 nebula
Keyword(s): cold interstellar medium, radio spectroscopy, radio recombination lines
Pages: 17 -- 27
DOI: https://doi.org/10.31577/caosp.2023.53.1.17
NASA ADS Abstract Service: 2023CoSka..53a..17V
Citation:
License: This work is licensed under a Creative Commons Attribution 4.0 International License

Abstract: Low-frequency carbon radio recombination lines (RRLs) serve as an effective probe of cold, partially ionized gas diagnostic. In this paper we report about studies of these lines towards the S140 nebula at UTR-2 near 26 MHz. As a spectrometer, the 4096-channel digital correlometer was used. Low-frequency carbon RRLs were detected for the S140 line of sight and its environs, the line of sight being shifted in 3° by declination to one and other side. For all three directions the similar relative line intensities were obtained. Measured line widths do not coincide with high-frequency RRLs line widths. This can tell us that a low-frequency line forming region is not associated with the S140 nebula itself. By an iterative analysis it was obtained that values of electron temperature T_e = 50 ÷ 100 K and electron density N_e = 0.01 cm^-3 most closely match our experimental data. Due to the fact that the sizes of the line forming region (or regions) exceed the solid angle of the S140 nebula, and due to the mismatch between the widths of low-frequency and high-frequency RRLs, and also based on our analysis of physical conditions of the line forming region it was proposed that low-frequency lines were formed in the local medium associated with HI clouds lying on the line of sight. Further observations and interpretation will help to describe the physical parameters of the medium in different Galactic directions.