On the link between column density distribution and density scaling relation in star formation regions

Abstract

We present a method to derive the density scaling relation $⟨n⟩\propto L^{-\alpha }$ in regions of star formation or in their turbulent vicinities from straightforward binning of the column-density distribution ($N$-pdf). The outcome of the method is studied for three types of $N$-pdf: power law ($7/5\le \alpha \le 5/3$), lognormal ($0.7\lesssim \alpha \lesssim 1.4$) and combination of lognormals. In the last case, the method of Stanchev et al. (2015) was also applied for comparison and a very weak (or close to zero) correlation was found. We conclude that the considered `binning approach' reflects rather the local morphology of the $N$-pdf with no reference to the physical conditions in a considered region. The rough consistency of the derived slopes with the widely adopted Larson's (1981) value $\alpha \sim 1.1$ is suggested to support claims that the density-size relation in molecular clouds is indeed an artifact of the observed $N$-pdf.

11 pages, 4 figures; to appear in the Bulgarian Astronomical Journal, vol. 27, 2017

References in corpus (1)

• Density scaling relation in Orion A: effects of region selection