1997/11/06 by Paolo Padoan, Mika Juvela, Mike Juvela +3 · 2 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Choked flow #Compressibility #Flow (mathematics) #Magnetohydrodynamics #Molecular cloud #Optical properties and cooling technologies in crystalline materials #Radiative transfer #Solar and Space Plasma Dynamics #Spectral line #Supersonic speed #astro-ph
paper · pdf · doi:10.1086/306060
33 pages, 12 figures included, 5 jpeg figures not included (fig1a, fig1b, fig3, fig4 fig5), submitted to ApJ
arxiv created 1997/11/06 · openalex publication_date 1998/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The dynamics of molecular clouds is characterized by supersonic random motions in the presence of a magnetic field. We study this situation using numerical solutions of the three-dimensional compressible magnetohydrodynamic (MHD) equations in a regime of highly supersonic random motions. The non-LTE radiative transfer calculations are performed through the complex density and velocity fields obtained as solutions of the MHD equations, and more than 5 × 10 5 spectra of 12 CO, 13 CO, and CS are obtained. In this way we build synthetic molecular clouds of 5 and 20 pc diameter, evolved for about one dynamical time from their initial configuration. We use a numerical flow without gravity or external forcing. The flow is super-Alfvénic. Synthetic data consist of sets of 90 × 90 synthetic spectra with 60 velocity channels, in five molecular transitions: J = 1 → 0 and J = 2 → 1 for 12 CO and 13 CO, and J = 1 → 0 for CS. Although we do not consider the effects of stellar radiation, gravity, or mechanical energy input from discrete sources, our models do contain the basic physics of magnetofluid dynamics and non-LTE radiation transfer and are therefore more realistic than previous calculations. As a result, these synthetic maps and spectra bear a remarkable resemblance to the corresponding observations of real clouds.