2017/03/31 by D. Kandel, A. Lazarian, D. Pogosyan
Physics and Astronomy · #Absorption (acoustics) #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atomic physics #Computational physics #Emissivity #Magnetic field #Magnetohydrodynamic turbulence #Magnetohydrodynamics #Mechanics #Meteorology #Optical depth #Optics #Physics #Quantum mechanics #Radiative transfer #Solar and Space Plasma Dynamics #Spectral line #Stellar, planetary, and galactic studies #Turbulence #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx1358
published as MNRAS 470, 3103-3123 (2017) · Published in MNRAS, minor changes to match the published version
openalex publication_date 2017/06/01 · arxiv created 2017/08/09 · arxiv updated 2017/08/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the effect of dust absorption on the recovery velocity and density spectra as well as on the anisotropies of magnetohydrodynamic turbulence using the velocity channel analysis (VCA), velocity coordinate spectrum (VCS) and velocity centroids. The dust limits volume up to an optical depth of unity. We show that in the case of the emissivity proportional to the density of emitters, the effects of random density get suppressed for strong dust absorption intensity variations arise from the velocity fluctuations only. However, for the emissivity proportional to squared density, both density and velocity fluctuations affect the observed intensities. We predict a new asymptotic regime for the spectrum of fluctuations for large scales exceeding the physical depths to unit optical depth. The spectrum gets shallower by unity in this regime. In addition, the dust absorption removes the degeneracy resulted in the universal K−3 spectrum of intensity fluctuations of self-absorbing medium reported by Lazarian & Pogosyan. We show that the predicted result is consistent with the available H ii region emission data. We find that for sub-Alfvénic and trans-Alfvénic turbulence one can get the information about both the magnetic field direction and the fundamental Alfvén, fast and slow modes that constitute MHD turbulence.