Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence?

Details Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence? Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence?

2010-06-14

arxiv.org/abs/1006.2826v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

6 pages, 6 figures, accepted for publication in MNRAS

Scientific paper

Recent observations of column densities in molecular clouds find lognormal distributions with power-law high-density tails. These results are often interpreted as indications that supersonic turbulence dominates the dynamics of the observed clouds. We calculate and present the column-density distributions of three clouds, modeled with very different techniques, none of which is dominated by supersonic turbulence. The first star-forming cloud is simulated using smoothed particle hydrodynamics (SPH); in this case gravity, opposed only by thermal-pressure forces, drives the evolution. The second cloud is magnetically subcritical with subsonic turbulence, simulated using nonideal MHD; in this case the evolution is due to gravitationally-driven ambipolar diffusion. The third cloud is isothermal, self-gravitating, and has a smooth density distribution analytically approximated with a uniform inner region and an r^-2 profile at larger radii. We show that in all three cases the column-density distributions are lognormal. Power-law tails develop only at late times (or, in the case of the smooth analytic profile, for strongly centrally concentrated configurations), when gravity dominates all opposing forces. It therefore follows that lognormal column-density distributions are generic features of diverse model clouds, and should not be interpreted as being a consequence of supersonic turbulence.

Affiliated with

Also associated with

No associations

Rating

Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Do Lognormal Column-Density Distributions in Molecular Clouds Imply Supersonic Turbulence? will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-103844