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C. Brunt

Publications and source records attributed to C. Brunt.

20 records · Page 2Linked to original sources
arXiv2006

Turbulent Gas Flows in the Rosette and G216-2.5 Molecular Clouds: Assessing Turbulent Fragmentation Descriptions of Star Formation

The role of turbulent fragmentation in regulating the efficiency of star formation in interstellar clouds is examined from new wide field imaging of 12CO and 13CO J=1-0 emission from the Rosette and G216-2.5 molecular clouds. The Rosette molecular cloud is a typical star forming giant molecular cloud and G215-2.5 is a massive molecular cloud with no OB stars and very little low mass star formation. The properties of the turbulent gas flow are derived from the set of eigenvectors and eigenimages generated by Principal Component Analysis of the spectroscopic data cubes. While the two clouds represent quite divergent states of star formation activity, the velocity structure functions for both clouds are similar. The sonic scale, lambda_S, defined as the spatial scale at which turbulent velocity fluctuations are equivalent to the local sound speed, and the turbulent Mach number evaluated at 1 pc, M_{1pc}, are derived for an ensemble of clouds including the Rosette and, G216-2.5 regions that span a large range in star formation activity. We find no evidence for the positive correlations between these quantities and the star formation efficiency, that are predicted by turbulent fragmentation models. A correlation does exist between the star formation efficiency and the sonic scale for a subset of clouds with L_{FIR}/M(H_2) > 1 that are generating young stellar clusters. Turbulent fragmentation must play a limited and non-exclusive role in determining the yield of stellar masses within interstellar clouds.

astro-ph↗
arXiv2000

Interstellar Turbulence: I. Retrieval of Velocity Field Statistics

We demonstrate the capability of Principal Component Analysis (PCA) as applied by Heyer & Schloerb (1997) to extract the statistics of turbulent interstellar velocity fields as measured by the energy spectrum, E(k)= k^-beta. Turbulent velocity and density fields with known statistics are generated from fBm simulations. These fields are translated to the observational domain, T(x,y,v), considering the excitation of molecular rotational energy levels and radiative transfer. Using PCA and the characterization of velocity and spatial scales from the eigenvectors and eigenimages respectively, a relationship is identified which describes the magnitude of line profile differences, deltav, and the scale, L, over which these differences occur, deltav=L^alpha. From a series of models with varying values of beta, we find, alpha = 0.33beta - 0.05 for 1 < beta < 3. This provides the basic calibration between the intrinsic velocity field statistics to observational measures and a diagnostic for turbulent flows in the interstellar medium. We also investigate the effects of noise, line opacity, and finite resolution on these results.

astro-ph↗