clump decomposition methods and the dqs tony wong university of illinois

Clump decomposition methods and the DQS Tony Wong University of Illinois Interstellar Turbulence Fourier transform power spectra (Lazarian & Pogosyan 2000) Wavelets (including -variance) Spectral correlation function (Rosolowsky et al. 1999) Principal component analysis (Brunt & Heyer 2002) Clumpfind (Williams et al. 1994) Gaussclumps (Stutzki & Gsten 1990) CPROPS (Rosolowsky & Leroy 2006) Statistical methods: Structural decomposition: NANTEN 12 CO Mopra 13 CO Mopra C 18 O SEST 1.2 mm Column density and 13 CO opacity 8 Highest opacity regions G Ring radius ~10 pc; consistent with 10 km s -1 expansion for 1 Myr -corrected total cloud mass is only slightly (~10%) larger than would be derived from the optically thin assumption with T ex =20 K. However, distribution of column densities differs significantly on the high end. Column density PDF -corrected Comparison with Ridge et al. (2006) Extinction (2MASS) CO emission (FCRAO) Ostriker, Stone, Gammie 2001 A log-normal volume density distribution is expected from isothermal turbulence The column density PDF should transition from log-normal to Gaussian as more independent zones along the line of sight are integrated. Comparison with simulations high B low B CLUMPFIND: Use a hierarchy of contour levels to identify emission maxima. Clumps are identified as closed contours in contour plot Contested emission assigned to nearest clump using friends of friends algorithm GAUSSCLUMPS: Model the cloud as a sum of triaxial Gaussian components. Can distinguish tight blends of clumps Clump properties follow immediately Tendency to create many small clumps CPROPS: Use contouring like CLUMPFIND, but do not try to divide contested emission. Identify local maxima larger than all neighbors Require >2 contrast above merge level with other maxima Segmentation into Clumps Clump Numbers - 13 CO CLFINDGAUSSCPROPS Clump Numbers - 13 CO CLFINDGAUSSCPROPS Number of clumps fraction of total flux decomposed 100%64%9.3% Distribution of Masses CLFINDGAUSS CPROPS Distribution of Radii CLFINDGAUSS CPROPS Luminosity vs. Radius CLFINDGAUSSCPROPS While molecular clouds as a whole have approximately constant surface density, clumps within them seem to have approximately constant volume density. Line width vs. Radius CLFINDGAUSSCPROPS No strong correlation, especially for latter 2 methods. Luminosity vs. Line width CLFINDGAUSSCPROPS Not independent of previous two relations! Virial vs. Luminous Mass CLFINDGAUSSCPROPS x-axis: T b R 2 y-axis: R 2 >>1: clump must be confined by external pressure ~1: clump is close to self-gravitating