The turbulence of the interstellar medium of active galaxies

Aims. The paper is devoted to the influence of hydrodynamic turbulence in the gaseous medium of active galaxies on the profile of the [CII] 158 μm emission line. Methods. From a sample of galaxies with observed profiles of the [CII] 158 μm line, we selected galaxies with a measured full width half maximum. The calculated rotational velocities of the disk galaxies in our selection proved to be clearly greater than 200 km s−1, even without taking dark mass into account. We assumed that the observed widths of the [CII] 158 μm line are due to turbulent eddies in the Kolmogorov cascade process of turbulent energy transfer, and we calculated the corresponding rates of transfer of this energy. In this process, turbulent energy dissipates, thereby heating the medium and causing excitation and subsequent luminescence in the [CII] 158 μm line. Results. The calculated rates of turbulent energy transfer – (k(1039 − 1044 erg s−1), with a coefficient k = 0.01 − 0.1) – are of the same order of magnitude as the observed luminosities in the [CII] 158 μm line (approximately a few 1037 − 1042 erg s−1). Moreover, a clear close connection exists between these quantities. The behavior of this dependence differs for starburst and active galactic nuclei galaxies, a difference that is probably due to varying kinematic conditions in the medium. To test the possibility of generating the maximum turbulent velocity of about 200 km s−1, we constructed the same dependence for a maximum velocity of 600 km s−1. In such cases, the dependence between the luminosity of the [CII] 158 μm line and the turbulent energy transfer rate remains unchanged.