Observational Diagnostics of Selfgravitating MHD Turbulence in Giant Molecular Clouds
Abstract
We study the observable signatures of selfgravitating magnetohydrodynamics (MHD) turbulence by applying the probability density functions (PDFs) and the spatial density power spectrum to synthetic column density maps. We find that there exists three characterizable stages of the evolution of the collapsing cloud which we term “early,” “intermediate,” and “advanced.” At early times, i.e., t\lt 0.15{t}_{{ff}}, the column density has a power spectral slope similar to nongravitating supersonic turbulence and a lognormal distribution. At an intermediate stage, i.e., 0.15{t}_{{ff}}\lt t≤slant 0.35{t}_{{ff}}, there exist signatures of the first cores in the shallower PDF and power spectrum powerlaw slopes. The column density PDF powerlaw tails at these times have line of sight averaged slopes ranging from 2.5 to 1.5 with shallower values belonging to simulations with lower magnetic field strength. The density power spectrum slope becomes shallow and can be characterized by P(k)={A}_{1}{k}^{{β }_{2}}{e}^{k/{k}_{c}}, where A_{1} describes the amplitude, {k}^{{β }_{2}} describes the classical powerlaw behavior, and the scale k_{c} characterizes the turn over from turbulence dominated to selfgravity dominated. At advanced stages of collapse, i.e., ≈ t\gt 0.35{t}_{{ff}}, the power spectral slope is positive valued, and a dramatic increase is observed in the PDF moments and the Tsallis incremental PDF parameters, which gives rise to deviations between PDFsonic Mach number relations. Finally, we show that the imprint of gravity on the density power spectrum can be replicated in nongravitating turbulence by introducing a deltafunction with amplitude equivalent to the maximum valued point in a given selfgravitating map. We find that the turbulence power spectrum restored through spatial filtering of the high density material.
 Publication:

The Astrophysical Journal
 Pub Date:
 July 2015
 DOI:
 10.1088/0004637X/808/1/48
 arXiv:
 arXiv:1505.03855
 Bibcode:
 2015ApJ...808...48B
 Keywords:

 dust;
 extinction;
 ISM: kinematics and dynamics;
 magnetic fields;
 magnetohydrodynamics: MHD;
 molecular data;
 stars: formation;
 turbulence;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted to ApJ