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  • The Pressure Structure of Molecular Clouds


    Abstract. Broadly, we seek to understand the role of pressure in star forming molecular clouds. We examine molecular line data of the Perseus region from the COMPLETE survey alongside radiative transfer-processed ‘observations’ of the turbulent simulations of S. Offner to try to (1) understand to what extent we can actually measure pressure through observations, and (2) study how pressure changes within a cloud’s substructure.


    1. Internal pressure in GMCs acts to resist collapse locally and is an important part of the force balance equation controlling the efficiency of star formation

    2. Pressure of the ambient ISM “external” to clouds may act to help confine them against dissipation on short timescales – i.e. clouds may be in pressurized virial equilibrium even if unbound according to simple virial analysis (Field, Blackman & Keto 2011).

    3. Clouds are complex, turbulent entities that contain hierarchical structure and both large- and small-scale features (in density, velocity, possibly magnetic fields).

    4. Molecular line observations of clouds reveal some of this structure but are limited to a small dynamic range in density (for a single tracer) and one dimension of the velocity field. Observations also represent only a snapshot in what is in reality a dynamic system. Simulations have the advantage of allowing the time evolution within clouds to be followed, and including the full (“true”) six-dimensional phase space information, but are heavily reliant on the (necessarily limited) input physics.

    5. Dendrograms represent a powerful tool for probing hierarchical structure and can be applied to real and simulated data to make progress on understanding the pressure structure within and external to clouds.

    6. We have analyzed data from COMPLETE and synthetic cubes from radiative transfer-processed turbulent simulations to attempt to clarify the role of pressure within clouds and in the star formation process.

    \(^{13}\)CO integrated intensity map of IC348 in Perseus.

    Expectations from Simple Scaling Laws


    Pressure scaling: \[P \propto \rho \sigma_v^2\]

    Density and velocit