Molecular clouds have power-law probability distribution functions (not log-normal)

Author(s)

Joao Alves, Marco Lombardi, Charles Lada

Abstract

We investigate the shape of the probability distribution of column

densities (PDF) in molecular clouds. Through the use of low-noise,

extinction-calibrated Planck-Herschel emission data for eight molecular

clouds, we demonstrate that, contrary to common belief, the PDFs of

molecular clouds are not described well by log-normal functions, but are

instead power laws with exponents close to two and with breaks between

AK≃0.1 and 0.2mag, so close to the CO self-shielding limit and not

far from the transition between molecular and atomic gas. Additionally,

we argue that the intrinsic functional form of the PDF cannot be

securely determined below AK≃0.1mag, limiting our ability to

investigate more complex models for the shape of the cloud PDF.

Organisation(s)

Department of Astrophysics

External organisation(s)

Università degli Studi di Milano-Bicocca, Harvard-Smithsonian Center for Astrophysics

Journal

IAU General Assembly Meeting

Volume

Publication date

08-2015

Austrian Fields of Science 2012

103003 Astronomy, 103004 Astrophysics

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