The Lognormal Probability Distribution Function of the Perseus Molecular Cloud: A Comparison of HI and Dust

Abstract

The shape of the probability distribution function (PDF) of molecular clouds is an important ingredient for modern theories of star formation and turbulence. Recently, several studies have pointed out observational difficulties with constraining the low column density (i.e. Av <1) PDF using dust tracers. In order to constrain the shape and properties of the low column density probability distribution function, we investigate the PDF of multiphase atomic gas in the Perseus molecular cloud using opacity-corrected GALFA-HI data and compare the PDF shape and properties to the total gas PDF and the N(H2) PDF. We find that the shape of the PDF in the atomic medium of Perseus is well described by a lognormal distribution, and not by a power-law or bimodal distribution. The peak of the atomic gas PDF in and around Perseus lies at the HI-H2 transition column density for this cloud, past which the N(H2) PDF takes on a powerlaw form. We find that the PDF of the atomic gas is narrow and at column densities larger than the HI-H2 transition the HI rapidly depletes, suggesting that the HI PDF may be used to find the HI-H2 transition column density. We also calculate the sonic Mach number of the atomic gas by using HI absorption line data, which yields a median value of Ms=4.0 for the CNM, while the HI emission PDF, which traces both the WNM and CNM, has a width more consistent with transonic turbulence.

Accepted to ApJL; comments welcome

References in corpus (20)

• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• What determines the density structure of molecular clouds ? A case study of Orion B with Herschel
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• Molecular clouds have power-law probability distribution functions
• Class 0 Protostars in the Perseus Molecular Cloud: A Correlation Between the Youngest Protostars and the Dense Gas Distribution
• The 21-SPONGE HI Absorption Survey I: Techniques and Initial Results
• Understanding star formation in molecular clouds II. Signatures of gravitational collapse of IRDCs
• Cold and Warm Atomic Gas around the Perseus Molecular Cloud. II. The Impact of High Optical Depth on the HI Column Density Distribution and Its Implication for the HI-to-H2 Transition
• Herschel's view of the large-scale structure in the Chamaeleon dark clouds
• Observational Diagnostics of Self-Gravitating MHD Turbulence in Giant Molecular Clouds
• Density probability distribution functions of diffuse gas in the Milky Way
• Cold and warm atomic gas around the Perseus molecular cloud I: Basic Properties
• THOR - The HI, OH, Recombination Line Survey of the Milky Way - The pilot study: HI observations of the giant molecular cloud W43
• Galactic interstellar turbulence in the southern sky seen through spatial gradients of the polarization vector
• The COMPLETE Nature of the Warm Dust Ring in Perseus
• HI-to-H2 Transitions in the Perseus Molecular Cloud
• On the fidelity of the core mass functions derived from dust column density data
• Tracing the general structure of Galactic molecular clouds using Planck data: I. The Perseus region as a test case

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• Gravitationally Bound Gas Determines Star Formation in the Galaxy
• The Transition from a Lognormal to a Power-Law Column Density Distribution in Molecular Clouds: An Imprint of the Initial Magnetic Field and Turbulence
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